determination of aquifer properties and...

QUEENSLAND UNIVERSITY OF TECHNOLOGY

School of Natural Resource Sciences

DETERMINATION OF AQUIFER PROPERTIES AND

HETEROGENEITY IN A LARGE COASTAL SAND

MASS: BRIBIE ISLAND, SOUTHEAST QUEENSLAND

by

Timothy J. Armstrong

B. App. Sc

SUPERVISOR

Dr. Malcolm Cox

Queensland University of Technology

A thesis submitted in partial fulfilment of the requirements for the Degree of Master

of Applied Science.

March, 2006

School of Natural Resource Sciences, Queensland University of Technology

Brisbane Queensland 4001 GPO Box 2423

Abstract

Aquifer heterogeneity within the large coastal sand island of Bribie Island,

Queensland, Australia, has an affect on groundwater occurrence and migration. The

stratigraphy of Bribie Island is complicated by the presence of low permeability

humate-cemented indurated sand layers.

Occurrences of indurated sand layers have previously been identified within many

unconsolidated profiles along the east coast of Australia and around the world.

Indurated sand layers are often discontinuous resulting in localised aquifer

heterogeneity. However, their regional significance is commonly underestimated.

The groundwater resource of Bribie Island is of commercial and environmental

significance to the surrounding bay area. Recent development proposals for the

groundwater resource necessitate an investigation into the nature of the water bearing

properties of the island aquifer and in particular the presence of aquifer

heterogeneity. Investigation of a “reference” transect across Bribie Island has

involved the drilling and development of monitoring wells and the performance of

hydraulic tests.

This study demonstrates how detailed measurement of stratigraphy, groundwater

levels, rainfall, barometric pressure and hydraulic testing can be used in conjunction

to identify and assess aquifer heterogeneity within a sand island environment.

Drill logs confirm the position of a palaeochannel within the sandstone bedrock that

extends from the mainland continuing under Bribie Island. The overlying sediment

profile is thickest within the palaeochannel. The Pleistocene and Holocene

unconsolidated profile reflects a prograding barrier island/strandplain formation.

The vertical sequence of sediments consists of units that range from offshore sandy

silts to foreshore and beach medium-fine grained sands.

An extensive indurated sand layer exists throughout the centre of the island. The

greatest thickness of indurated sand is located centrally on the island beneath the

main beach ridge system. The indurated layer at its thickest is approximately 5-8 m

thick, but over much of the island the thickness is 1-3 m. The top of indurated sand

layer is generally 1-3 m above mean sea level.

Hydrographs from a network of groundwater monitoring wells illustrate that the

groundwater resources across the reference transect can be divided into a shallow

unconfined water table aquifer and basal confined aquifers. These upper and lower

aquifers are characterised by different hydrological processes, physico-chemical

properties, and water chemistry.

The stratification of water levels across the reference transect and the relatively flat

piezometric surface are in contrast with the classical “domed” water table aquifer

expected of a barrier island. Stratified head gradients through the Bribie Island

aquifers suggest groundwater migration to depth is impeded by the indurated sand

layer. An elevated shallow water table results from the mounding of water above the

indurated sand layer. The indurated sand layer is extensive across the reference

transect.

The elevated unconfined groundwater is usually stained with organic matter (“black

water”), where as groundwater sourced from beneath the indurated sand layer is

colourless (“white water”). The unconfined groundwater is also distinguished by

low pH, low bicarbonate concentrations and high concentrations of organic carbon.

Interaction between unconfined groundwater and surface water are also evident.

Hydraulic tests indicate that each of the unconsolidated units across the reference

transect has distinctive hydraulic characteristics. Estimates of vertical and horizontal

hydraulic conductivity of the unconfined aquifer are two to three orders of magnitude

greater than estimates for the indurated sand layer. Beneath the indurated sand layer

hydraulic conductivities of the basal aquifers are also greater by two to three orders

of magnitude than estimates for the indurated sand layer. The lower hydraulic

conductivity within the indurated sand layer is responsible for the local semi-

confinement of the basal aquifers.

Contents

Abstract

List of Figures

List of Appendices

Statement of Original Authorship

Acknowledgements

Glossary

1.0 INTRODUCTION 1 1.1 Aim 2

1.2 Objectives 2

1.3 Significance of Research 2

2.0 BACKGROUND TO MATERIALS AND EVOLUTION 3 2.1 Beaches, Strand Plains and Barrier Coasts 3

2.2 Barrier Coasts 5

2.2.1 Coast environments 5

2.3 Barrier types and facies 6

2.3.1 Prograded barriers 8

2.4 Barrier Coast Hydrology 9

2.4.1 Surface water 9

2.4.2 Groundwater occurrence 10

2.4.3 Porosity and aquifer storage 11

2.4.4 Hydraulic conductivity 13

2.4.5 Aquifer heterogeneity 15

2.4.6 Hydrochemistry 17

2.5 Nature of Indurated Sand 18

3.0 PHYSICAL SETTING OF BRIBIE ISLAND 21 3.1 Regional Setting 21

3.2 Geology 24

3.3 Geomorphology 26

3.3.1 Pleistocene beach ridge system 26

3.3.2 Holocene beach ridge system 29

3.3.3 Active foredune system 29

3.3.4 Estuarine tidal delta system 29

3.4 Drainage System 30

3.5 Climate 30

3.6 Evaporation 31

3.7 Groundwater Recharge 32

3.8 Vegetation 33

3.9 Land Use 33

4.0 HYDROGEOLOGICAL STUDIES OF BRIBIE ISLAND 35

5.0 METHODS 39 5.1 Drilling and Hydraulic Testing 40

5.1.1 Drilling program 40

5.1.2 Well construction 42

5.1.3 Water level monitoring 45

5.1.4 Bailer tests 46

5.1.5 Pumping tests 47

5.2 Hydraulic Tests Analysis 50

5.3 Water and Sediment Sampling 58

5.3.1 Sediment samples 58

5.3.2 Age dating samples 59

5.3.3 Age dating analysis 59

5.3.4 Water sampling 60

5.3.5 Elemental analysis 62

6.0 RESULTS 64 6.1 Island Stratigraphy 65

6.1.1 Aquifer description and distribution 65

6.2 Island Evolution and Age 69

6.3 Island Hydrology 70

6.3.1 Groundwater levels 72

6.4 Barometric Efficiencies 77

6.5 Water Geochemistry 82

6.5.1 Physico-chemical properties 82

6.5.2 Major ion chemistry 84

6.5.3 Water types 85

6.5.4 Organic carbon content 87

6.6 Aquifer Hydraulic Testing 88

6.6.1 Bailer tests 88

6.6.2 Pumping test 1 91



7.0 HYDRAULIC TEST ANALYSIS AND

INTERPRETATION 99 7.1 Bailer Tests 99

7.2 Pumping Tests 102




8.0 DISCUSSION 115 8.1 Comparison of Hydraulic Conductivities 115

8.2 Conceptual Hydrogeological Framework 117

9.0 CONCLUSION 121

REFERENCES

APPENDICES

List of Figures

Figure

1. Comparison of barrier island, strandplain and tidal flat morphologies 4

2. Geometry and morphological relationship of barrier types, Bribie Island (1a) 7

3. Cross section of a typical barrier island, and barrier facies model 9

4. Fresh groundwater water flow through a homogenous and isotropic barrier island

11

5. Range of hydraulic conductivity values of earth materials 14

6. Fresh groundwater flow through a heterogeneous barrier island 16

7. Location of Bribie Island in Moreton Bay, Queensland, Australia 21

8. Geographical map of Bribie Island 22

9. Bribie Island topographical map 23

10. Geological map of Bribie Island 24

11. Aquifer base contour map of Bribie Island 25

12. Lithological map of Bribie Island 27

13. Thickness of indurated sand layer for Bribie Island 28

14. Rainfall data for Bribie Island years 1993 to 2000 31

15. Previous monitoring well locations 38

16. Location of current groundwater monitoring wells 41

17. Typical construction method for monitoring wells 44

18. Manual electrified tape measure for the monitoring of water levels (photo) 45

19. Automatic groundwater level logging equipment and rainfall gauge (photo) 45

20. Schematic illustration of bailer hydraulic test 47

21. Schematic illustration of confined drawdown and cone of depression 48

22. Schematic illustration of cones of depression in pumping wells 49

23. Schematic illustration of the mechanics of a bailer test 52

24. Groundwater flow during a pumping test 53

25. Analysis of data from pumping test with the Theis method 56

26. Locations of surface water sampling points 61

27. Geological cross-section of Bribie Island across the reference transect D-D′ 67

28. Vertical sequence of progradational barrier sequence 68

29. Glacio-eustatic sea level curve for the last 340 000 years 71

30. Hydrographs of water levels from nested monitoring wells 74

31. Hydrographs from automatic loggers on monitoring wells 127 and 090 75

32. Water level contours across the reference transect 76

33. Flow net across the reference transect using averaged groundwater levels 71

34. Computation of barometric efficiency 81

35. Barometric response functions 82

36. Tri-linear diagram of major ion chemistry for groundwater and surface water

86

37. Summarised transect D-D' showing bailer test wells 88

38. Rising head plots derived from bailer testes of foredune and beach sand aquifer

89

39. Rising-head plots derived from bailer testes of swale deposits 90

40. Rising-head plots derived from bailer testes of indurated sand layer 91

41. Vertical cross section of transect D-D′ (pumping test 1) 92

42. Response of monitoring wells during pumping test 1 93


44. Response of monitoring wells during pumping test 2 95

45. Influence of barometric pressure during pumping test 2 96


47. Response of pumping well and monitoring well during pumping test 3 98

48. Plots of bailer test results based on lithological groupings 100

49. Analysis of recovery data from pumping test 1 103

50. Analysis of recovery data from pumping test 2 105

51. Theis analysis of drawdown data from pumping test 3 106

52. Cooper-Jacob analysis of drawdown data from pumping test 3 108

53. Schematic cross section and plan of an aquifer with a straight barrier boundary

109

54. Calculation of radius to image well from Cooper-Jacob plot 111

55. Schematic cross section including barrier boundary conditions 113

56. Stallman analysis of drawdown data from pumping test 3 114

57. Conceptual hydrogeology of Bribie Island including aquifer heterogeneity 120

List of Tables

Table

1. Porosity ranges for unconsolidated sediments 12

2. Specific yield in percent for unconsolidated sediments 12

3. Annual rainfall from registered stations located on Bribie Island 30

4. Mean monthly rainfall – Bongaree 31

5. Mean monthly evaporation – Brisbane 32

6. Well type and slotted casing lengths of monitoring wells across the reference

transect 42

7. Details of pumping tests 50

8. Sediment sampled details for OSL analysis 59

9. Calculated burial ages of sediment samples from Bribie Island 69

10. Barometric efficiencies 79

11. Physico-chemical parameters for groundwater and surface water 83

12. Major ion concentrations for groundwater and surface water 85

13. Total dissolved organic carbon concentrations and charge balances 87

14. Hydraulic conductivity values determined from bailer tests 99

15. Vertical hydraulic conductivity estimates based on head gradients 101

16. Hydraulic conductivity and specific storage estimates 102

17. Previous estimates of hydraulic conductivity for Bribie Island 115

18. Comparative estimates of hydraulic conductivity 117

List of Appendices

Section A: Associated publications

A Chemical character of surface waters on Bribie Island: a preliminary

assessment. (extended abstract)

B The relationship between groundwater and surface water character and

wetland habitats, Bribie Island, Queensland (conference paper)

C Controls over aquifer heterogeneity within a large sand island and analysis by

hydraulic testing, Bribie Island, Queensland, Australia (accepted manuscript -

Hydrogeology Journal)

Section B: Data

D Stratigraphic Logs

E Sediment Age Dating

F Groundwater Level Data

G Physico-chemical Data

H Major and Minor Ion Chemistry

I Calculation of Organic Anion Concentration

Statement of Original Authorship

The work contained in this thesis has not been previously submitted for a degree or

diploma at any other higher education institution. To the best of my knowledge and

belief, the thesis contains no material previously published or written by another

person except where due reference is made.

Signed: ……………………………………………………………………………...

Date: ………………………………………………………………………………..

Acknowledgements

I would like to take this opportunity to thank everyone who has helped with this

project in any way. Successful completion of this study has been made possible

through the practical and professional assistance of many people and institutions, in

particular;

• Dr Malcolm Cox (Principal supervisor)

The expertise and guidance provided to me throughout the project has been

invaluable. Thank you for your encouragement, I am greatly appreciative.

• John Harbison

Thank you for your support and encouragement throughout the project.

Your contributions to fieldwork, hydrogeological discussion and to the

writing process are greatly appreciated.

• Queensland University of Technology

Dr Micaela Preda, Dr Brendan Brooke, Sharron Price, Whathsala Kumar,

Bill Kwiecien

• Caloundra City Council

Bill Haddrill

• Department of Natural Resources, Mines and Energy

Peter Cochrane, Robert Ellis and Bill Mead

• Department of Primary Industries - Forestry

Stan Ward and Dr. Ken Bubb

• Queensland Parks and Wildlife

Bribie Island National Park Rangers

• PRCCA (Pumicestone Region Catchment Coordination Association)

• Pacific Harbour

• HLA Envirosciences Pty. Ltd.

• The Natural Heritage Trust - funding under project (992417)

• Collaborative funding

Caboolture Shire Council and Department of Primary Industry Forestry –

Beerburrum Office

• Thank you to all my friends

• Thank you to all my family

Glossary

• Aquifer

A formation that contains sufficient saturated permeable material to yield

significant quantities of water to wells or springs.

• Aquitard

A saturated unit of low hydraulic conductivity that can store and slowly

transmit groundwater either upward or downward depending on the

vertical hydraulic gradient.

• Barrier boundary

Boundaries that inhibit groundwater flow. Examples are faults, bedrock,

or thinning of an aquifer.

• Conceptual model

A simplified representation of the groundwater system that indicates flow

directions and boundary conditions affecting flow.

• Cone of Depression

A depression in the water table or piezometric surface surrounding a

pumping well. The shape of this depression is similar to an inverted cone.

• Confined Aquifer

An aquifer whose upper and lower boundaries are impervious and in

which the fluid pressure is greater than atmospheric pressure. The water

level in a well penetrating a confined aquifer will rise above the base of the

upper confining layer.

• Darcy’s Law

An equation that relates the volume of water per time moving through a

given cross-sectional area of aquifer to a particular potentiometric head

gradient.

• Drawdown

The amount of water level change from the static water level position

during a pumping test.

• Flow Net

A two-dimensional representation of steady-state groundwater flow. The

flow net consists of intersecting lines of equal hydraulic head and

associated flow lines.

• Heterogeneity

Relating to the physical properties of an aquifer from point A to point B,

including packing, thickness and cementation. Heterogeneous units differ

in physical properties from point A to point B.

• Homogeneity

Relating to the physical properties of an aquifer from point A to point B,

including packing, thickness and cementation. Homogenous units have

similar properties from point A to point B.

• Hydraulic Conductivity

A value representing the relative ability of water to move through a

geologic material of a given permeability.

• Indurated Sand

Quartz sand grains cemented together by the infilling of pores by a variety

of cements, predominately organic matter and clays.

• Perched Water

Unconfined groundwater separated from an underlying main body of

groundwater by an unsaturated zone.

• Permeability

The ability of a porous medium to transmit fluid under a given gradient.

• Piezometric Surface

Imaginary surface that represents the static head. The surface is defined

by the levels to which water will rise in a well when that well penetrates an

aquifer.

• Porosity

The volume of void space within earth materials.

• Specific Storage

The amount of stored water released from a unit volume of aquifer per unit

decline in head.

• Storativity (= Storage Coefficient)

The volume of water released or taken into storage per unit plan area of

aquifer per unit change of head.

• Swale

An extensive depression between series of beach ridges, representing a

period of cessation of progradation.

• Unconfined Aquifer

An aquifer whose upper surface is at atmospheric pressure.

• Water Table

The top of the saturated zone of an unconfined aquifer where the pressure

is at atmospheric pressure.

1

1.0 INTRODUCTION

Sand island formation by the dominant process of beach ridge progradation suggests

that the associated groundwater aquifers may be relatively homogenous. However,

the complex stratigraphic framework of many sand islands produce substantial

aquifer heterogeneity. Heterogeneity of aquifers within sand islands can

significantly affect groundwater occurrence and groundwater movement through the

island (e.g. Harris 1967; Bolyard et al. 1979; Vacher 1988; Burkett 1996; Collins and

Easley 1999; Anderson et al. 2000; Ruppel et al. 2000). Aquifers typical of sand

islands can contain substantial reserves of freshwater that support environmental

flow to wetland habitats, water supply for the island community and offshore

discharge.

Important features of the southeast Queensland coastline are a series of large sand

islands that contain freshwater hydrological systems that store vast quantities of

groundwater. Bribie Island is currently used as a source of freshwater by local

authorities and various land users. Excessive use of groundwater in such settings has

the potential for inducing saltwater intrusion, desiccation of wetlands and

degradation of groundwater quality.

Throughout coastal southeast Queensland the elevation of shallow groundwater

across indurated sand profiles has been well documented (Laycock 1975; Thompson

1981; Reeve et al. 1985; Ward and Grimes 1987; Thompson et al. 1996).

Additionally, Cox et al. (2002) and Ezzy et al. (2002) suggest that the indurated sand

profiles within the coastal area not only produce a degree of separation of

groundwater bodies, but that differences in the chemical composition of the waters is

also quite evident. It is therefore apparent that due to the reduced porosity and

permeability, extensive indurated sand profiles can play a dominant role in

hydrological processes in coastal areas.

A conceptual model for groundwater occurrence on Bribie Island was developed by

Harbison and Cox (1998) and a two-aquifer system proposed. It has been noted that

even small-scale heterogeneities can be important in controlling groundwater flow

2

within sand island environments (Anderson et al. 2000). This current study

investigates the heterogeneity of the Bribie Island aquifers and is designed to

establish the water-bearing properties of aquifer material and presents new data of

stratigraphy, groundwater levels, rainfall, barometric pressure and hydraulic testing.

1.1 Aim

The aim of this research is to quantify aquifer heterogeneity within the

unconsolidated sands of Bribie Island by use of hydraulic testing and determine

vertical and lateral flow of groundwater within a detailed transect of the island and

relate this to groundwater chemistry.

1.2 Objectives

Several research objectives are proposed to achieve the aim of this study:

• Further define the geological framework of Bribie Island with particular

reference to the spatial distribution of stratigraphic units across a reference

transect.

• Identify trends in groundwater levels that may reflect aquifer heterogeneity

across the reference transect.

• Identify spatial variation of groundwater and surface water chemistry that

may highlight processes such as groundwater migration and flow.

• Determine aquifer hydraulic properties of various stratigraphic units with

reference to aquifer heterogeneity across the reference transect.

• Develop a conceptual hydrogeological model including aquifer heterogeneity

of the central section of Bribie Island.

1.3 Significance of Research

The outcomes of this research will have implications for:

• Greater understanding of causes and distribution of aquifer heterogeneity

within coastal environments particularly sand islands.

• Provide information on the role of aquifer heterogeneity and the recharge and

movement of coastal groundwater.

• Contribute hydrogeological information towards an effective groundwater

management plan for Bribie Island.

3

2.0 BACKGROUND TO MATERIALS AND

EVOLUTION

Accumulations of masses of sand are a common occurrence along the east coast of

Australia (e.g. Stephens 1992; Thom 1984; Roy et al. 1994). These coastal sand

bodies are usually related to the position of sea level and are often highly dynamic in

form, and in cases where well developed, these sand masses can host major supplies

of groundwater. The Bribie Island sand mass is described as a partially drowned

extensive strandplain of prograded Pleistocene to Holocene beach ridges (Lang et al.

1998); a distinctive elongate sand spit forms the northern extension of the island.

To enable an understanding of the internal structure, and the occurrence of

groundwater on Bribie Island, some understanding of the evolution and sedimentary

composition of a prograded sand island is necessary. To provide this background a

summary of the geology, morphology and hydrogeology of barrier coasts follows.

2.1 Beaches, Strand Plains and Barrier Coasts

Wave dominated sandy shorelines are often characterised by elongate, shore-parallel

sand deposits. These can occur as single mainland-attached beaches, broader beach-

ridge strandplains, or as barrier islands (Reinson 1984). The prime characteristics of

beaches, strandplains and barrier islands are derived from marine inundation during

rising sea level, and reworking of sediments, as distinct from direct fluvial influx.

These systems are supplied by longshore transport of river-derived sediments,

onshore transport of shelf sediments, erosion of local headlands, and by small coastal

streams (Galloway and Hobday 1983). Migrating sediment is concentrated in barrier

complexes, tidal flats, or may accrete directly on the mainland as strandplain

beaches. The contrasting morphologies of barrier/lagoon and strandplain coasts are

shown in Figure 1.

Barrier islands possess some features of strandplains and are transitional to them in

character (McCubbin 1982; Reinson 1984). For example, barrier islands can consist

of a single active barrier beach (transgressive barrier), or a series of parallel beach

ridges and swales situated behind the active beach shoreline (prograded barrier).

4

Additionally, the prograding barrier typically encloses an extensive back barrier

lagoon/estuary. This lagoonal or estuarine water body distinguishes the prograding

barrier from a strandplain; otherwise the two systems are genetically very similar

(Reinson 1984). An important variable between these systems is the position of sea

level.

Figure 1. Comparison of contrasted morphologies of A) barrier/lagoon, B) strandplain coasts and C)

tidal flats and their relation to different water bodies (after Galloway and Hobday 1983)

Strandplain systems are broad sheet-like, strike-elongate sand bodies that develop by

successive seaward accretion of beach ridges (Galloway and Hobday 1983), and their

multiple beach ridges are separated by narrow, marshy swales. The vertical

5

strandplain sequence is similar to that of a prograding barrier island, grading from

shoreface sand, silt, and mud into quartzose beach sands. The morphological

character of Bribie Island best fits the model of a “drowned” strandplain.

Additionally, strandplains lack the extensive tidal channels associated with low-tidal

and sub-tidal sand bodies (Figure 1).

2.2 Barrier Coasts

Often the term “barrier coast” is applied to coastal, unconsolidated sediment bodies

(islands or drowned strandplains) that are elongate and parallel to the shoreline.

Typically, these sand masses impede drainage from the mainland and are separated

in whole or in part by an estuary or lagoon, swamp or marsh, and/or a sand or mud

flat (McCubbin 1982; Reinson 1984; Thom 1984; Boyd et al. 1992; Davis 1994).

Barrier coasts currently comprise approximately 10-15% of the world’s total

coastline (Glaeser 1978; Summerfield 1991). Considering such a wide global

distribution, this type of coastal setting is of particular importance in respect to

environmental status and hydrological processes.

There is great variation in the type, shape, size, and age of these coastal barriers.

However, there are three common primary requirements for the formation of all

barriers (Davis 1994):

1. a significant sediment supply,

2. marine and wind processes that will develop and maintain the barrier,

and

3. a geomorphic setting where barrier formation can take place.

2.2.1 Coast environments

A number of major geomorphic features are recognised as being common to barrier

systems (Galloway and Hobday 1983; Reinson 1984; Thom 1984); a) the sandy

barrier complex, b) the enclosed body of water behind the barrier (lagoon/estuary),

and c) the channels that cut through the barrier and connect lagoon and sea.

Each environment is characterised by distinct lithofacies. Typically, the barrier

(predominantly sand) is partially vegetated and consists of dune ridges landward of

6

the sub-aerial beach. These sub-aerial beaches may or may not be inundated during

high magnitude storm surge conditions (Thom 1984). The enclosed or partly

enclosed body of water (lagoon or estuary) and associated back barrier (sand or tidal

flats) lie behind the barrier complex (Thom 1984). The lagoonal sedimentary

sequences generally consist of interbedded and interfingering sand, silt and mud

facies characteristic of a number of overlapping sub-environments (Reinson 1984).

Channel inlets provide water movement between the back barrier and open ocean

environments during each tidal cycle. Varying tidal ranges result in inlets of varying

character, in particular the size of the inlet and the longshore migration rate

(Galloway and Hobday 1983). The deepest parts of most channel inlets are

dominated by ebb currents and typically have an erosional base marked by coarse lag

deposits (Reinson 1984).

2.3 Barrier types and facies

Barrier coast development is favoured by relatively flat, low-gradient continental

shelves, abundant sediment supply, and low to moderate tidal range (Glaeser 1978).

The origin of barriers has been attributed to at least three distinct mechanisms:

1. the vertical growth and emergence of offshore bars (bar emergence)

2. down drift growth of spits (spit elongation)

3. detachment of beach ridges from the mainland by a rise in sea level

(ridge engulfment)

The third mechanism is most likely to occur in coastal zones of low relief (Swift

1975), while barriers built by coastwise elongation may be more common along

higher relief coastal zones (Glaeser 1978). Bar emergence is considered less

influential in the development of barrier coastlines, a process which is discussed in

detail by Otvos (2000). Clear distinction is often difficult among these various

modes of origin, particularly as many barriers show evidence of composite

development and modification.

To achieve some clarification, four primary modes of barrier formation exist (Roy

and Thom 1981; Galloway and Hobday 1983; Reinson 1984; Thom 1984) and have

been termed:

7

1. prograded barrier

2. stationary barrier

3. receded barrier

4. episodic transgressive barrier

Typically, the first three are recognised as the most significant modes of barrier

development, however, the inclusion of the fourth mode of formation is necessary to

account for the large sands islands of Fraser, Moreton, and North Stradbroke that

occur on the high-energy east coast of Australia (Stephens 1992; Thom 1984).

Figure 2 illustrates the sectional geometry and morphological relationship of these

four types of barrier formation.

Figure 2. Generalised diagram illustrating the sectional geometry and morphological relationship of

four barrier types (including some variants) that occur on the high-energy east Australian coast

including Bribie Island (1a) and Moreton Is, Nth Stradbroke Is, and Fraser Is (4a) (after Thom 1984)

8

Strandplain deposits such as that of Bribie Island are common on the relatively low-

relief coastline of Queensland (Stephens 1992; Jones 1993). The classification of a

strandplain by Thom (1984) includes prograded barriers that contain the presence of

a parallel ridge/swale pattern (Figure 2, 1a). This pattern can be seen on maps and

aerial photographs of Bribie Island and is characteristic of the prograding evolution

of the island.

2.3.1 Prograded barriers

Prograded barriers or strandplain complexes are characterised by multiple, coast

parallel beach or foredune ridges (Figure 2) and require abundant supplies of near

shore sand for this type of barrier formation (Thom 1984). Sand accumulation takes

place on the beach face and is blown inland onto low-relief foredune ridges where it

is bound by vegetation. Over time these dune sands are subjected to leaching and

soil development. Further accumulation results in seaward migration of the beach

face and the formation of either a beach ridge or strandplain (Thom 1984); narrow

marshy swales typically develop between the ridges (Galloway and Hobday 1983).

These ridges and swales characteristically have amplitude of 3-5 m, often reaching

elevations of 7-10 m above sea level (Thom et al. 1978).

In respect to sediment type and grain size, the typical prograding sequence becomes

coarser upwards from alternating sand and clay of the shelf and lower shoreface, to

sand of the upper shoreface and beach (Galloway and Hobday 1983). Drilling data

from barriers on the east coast of Australia show the beach sands to be uniformly fine

to medium grained and moderately well sorted (Roy et al. 1994). As shown in

Figure 3 the progradational origin of the barrier as well as the coarsening upward

profile of the prograding stratigraphic model.

9

Figure 3. A) Cross-section of a typical barrier island, showing progradational origin of the main

beach ridge system (after McCubbin 1982), B) barrier facies model of prograding barrier island

stratigraphic sequence (after Reinson 1984)

2.4 Barrier Coast Hydrology

A major role of barrier coastlines is in habitat creation, such as sheltering fragile

estuaries and marshlands that serve as incubators for marine organisms.

Additionally, barriers contribute to the cycling of nutrients and other materials

through the natural wetland habitats (Ruppel et al. 2000). A certain amount and

quality of freshwater is therefore needed by all physical, chemical and biological

systems associated with barriers.

All naturally occurring freshwater on these barriers originates from precipitation.

Although rainfall is the most prevalent type of precipitation on barrier coastlines,

precipitation can also take the form of snow, dew condensation and fog interception

(Urish 1977). Freshwater occurrence on barriers can be considered as two forms (a)

surface water, and (b) groundwater, although they may be connected.

2.4.1 Surface water

Surface water drainage patterns are typically little developed and may be diffuse in

character along barrier coastlines due to the low-relief morphology and the highly

transmissive surface sediments. However, despite the highly transmissive upper

dune sands, surface water accumulation can occur throughout many parts of the

10

barrier system. Surface water often occurs within the marshy swales between the

dune ridges. Additionally, if a swale is sufficiently deep it may intersect elevated

groundwater resulting in a “window” into the water table. Open bodies of surface

water are typically restricted to a narrow strip along the coastline behind the foredune

ridges. These water bodies often occur as brackish lagoons which are tidally affected

and are typically separated from the sea by small sand bars that are often breached

during severe storm events.

2.4.2 Groundwater occurrence

Barrier islands contain variable reserves of freshwater, despite being surrounded by

seawater. Precipitation continuously infiltrates permeable island sediments, and a

freshwater body develops as saltwater is displaced (Collins and Easley 1999). Figure

4 illustrates the development of a typical freshwater lens beneath a homogenous and

isotropic barrier island.

In barrier islands, groundwater flow is approximately normal to the long axis of the

island, and the phreatic aquifer takes the form of a Dupuit-Ghyben-Herzberg (DGH)

freshwater lens partially or wholly underlain by more dense saltwater (Urish 1977;

Ruppel et al. 2000). These lenses typically occur under islands that are small, very

permeable, and/or lightly recharged (Vacher 1988).

The DGH principle is a combination of the Dupuit assumption of horizontal flow and

the Ghyben-Herzberg principle that states when a freshwater lens overlies saltwater

water in homogenous and isotropic material, the freshwater lens will extend below

mean sea level (MSL) at a ratio of 40:1 (Harris 1967; Vacher 1988). For an island

characterised by homogenous and isotropic hydraulic properties and similar values

for mean sea level on both the lagoon and ocean sides, the DGH lens should be

symmetrical as illustrated in Figure 4 (Ruppel et al. 2000).

11

Figure 4. Fresh groundwater water flow through a barrier island of homogeneous and isotropic

sedimentary composition, where hf = the head of freshwater above mean sea level and Z is the depth

of the freshwater lens (after Harris 1967)

However, in most islands it is inappropriate to view the boundary between fresh and

saline groundwater as the sharp interface that is generally inferred in respect to the

DGH principle (Vacher 1988). The actual state of the lens is highly dynamic and

influenced by many factors that lead to a transitional zone of finite thickness (Urish

1977; Vacher 1988). The size and position of the transitional zone can be affected

by numerous factors such as higher mean sea level (MSL) on the ocean side of the

island than the lagoon side, tidal action from both sides of the island, freshwater

extraction via evapotranspiration and pumping, recharge amount and variability, and

hydraulic properties of the island aquifer (Harris 1967; Urish 1977; Vacher 1988;

Ruppel et al. 2000).

2.4.3 Porosity and aquifer storage

The amount of groundwater a barrier island aquifer can take in or release for a given

change in head controls the amount of groundwater that can be stored. The amount

of water an aquifer can hold in storage is determined by its porosity (Weight and

Sonderegger 2000); the porosity (n) of a material is the percentage of the formation

that is void of material (Fetter 1994). The general range of porosities that can be

expected for some typical sediments is listed in Table 1.

12

Table 1. Porosity ranges for unconsolidated sediments (after Fetter 1994)

Sediment type Percentage of void space

Well sorted sand or gravel 25 – 50

Sand and gravel, mixed 20 – 35

Glacial till 10 – 20

Silt 35 – 50

Clay 33 – 60

Porosity within a barrier island is governed by the function of size, shape and

arrangement of the sediment grains (Weight and Sonderegger 2000). The porous

voids are typically filled with air or fluid. Primary porosity between the sediment

grains forms during the formation of a barrier island. Secondary porosity is limited

on a sand island and relates to features that occur after the deposit has formed such as

pathways made by vegetation roots and animals burrows. The porosity of an aquifer

can also be reduced; fine-grained material can be flushed into shallow aquifers where

it fills void spaces.

The specific yield (Sy) of an aquifer is the ratio of the volume of water that drains

from a saturated aquifer by gravity, to the total volume of the aquifer (Fetter 1994).

Table 2 lists a number of sediment types and the typical specific yield as percent.

Table 2. Specific yield in percent for unconsolidated sediments (after Fetter 1994)

Material Maximum Minimum Average

Clay 5 0 2

Sandy clay 12 3 7

Silt 19 3 18

Fine sand 28 10 21

Medium sand 32 15 26

Coarse sand 35 20 27

Gravely sand 35 20 25

Since specific yield represents the volume of water that an aquifer will yield by

gravity drainage, with specific retention (Sr) the remainder, the sum of the two is

equal to porosity (Fetter 1994): n = Sy + Sr

13

Storativity (S) is a dimensionless value assigned to an aquifer and relates to the

amount of water an aquifer can store. The storativity for an unconfined aquifer is

typically taken to be equal to the specific yield, and has a range of 0.03 to 0.3 (Fetter

1994). In confined aquifers the water released from storage is a function of the

compressibility of the aquifer materials and the compressibility of water and is

expressed as specific storage (Ss) (Weight and Sonderegger 2000). Storativity values

for confined aquifers (Ss x aquifer thickness) can range from 10-3 to 10-6. Typically,

aquifers that have a storativity value between 0.03 and 10-3 are described as leaky or

semi-confined aquifers.

2.4.4 Hydraulic conductivity

Groundwater contained within the pore spaces of an aquifer is capable of moving

from one void to another. Thus, it is the ability of an aquifer to transmit water that,

together with its ability to hold water, constitute the most significant hydrogeologic

properties (Fetter 1994). Darcy’s Law defines the quantity of groundwater

movement through porous material:

KAiQ −= (1)

Where;

Q = Volumetric discharge rate (L3/t), and L = length or distance

K = Hydraulic conductivity (L/t)

A = b x w, the cross-sectional area perpendicular to flow (L2), [in horizontal flow,

the saturated thickness of the aquifer (b) multiplied by the width of aquifer (w)]

i = Hydraulic gradient (L/L) or slope to the potentiometric surface

Darcy’s law expresses that the volumetric rate (Q) of groundwater is proportional to

the proportionality constant (hydraulic conductivity, K) of the porous media and the

change in head over the length of the material (i.e. hydraulic gradient) (Fetter 1994;

Weight and Sonderegger 2000). The negative sign indicates that the flow is in the

direction of decreasing hydraulic head. Therefore, hydraulic conductivity is

dependant upon the nature of the porous medium and is a measure of the rate at

which water can move through the permeable medium. Hydraulic conductivity may

also be referred to as the coefficient of permeability.

14

Hydraulic conductivity has the dimensions of length over time (L/t). Typical units of

expression are m/day or cm/sec, and hydraulic conductivity values for earth materials

can range over twelve orders of magnitude (Weight and Sonderegger 2000). The

ranges of hydraulic conductivity values for various materials are illustrated in

Figure 5.

Figure 5. Range of hydraulic conductivity values of earth materials (after Weight and Sonderegger

2000)

A barrier island typically composed of silty sands and clean sands will therefore have

a relatively narrow range of hydraulic conductivity from 10-2 to 102 depending upon

the lithology of the island (Figure 5). Due to the relatively high hydraulic

conductivity of barrier islands, a decrease in permeability may have a substantial

affect on the groundwater system.

Estimation of hydraulic conductivity can be made by a number of established

methods. The hydraulic conductivity of unconsolidated sands can be estimated from

the grain-size distribution of a sample by the Hazen method (1911). The effective

grain-size is determined from a grain-size distribution plot, and together with a

sorting coefficient is related to hydraulic conductivity (Fetter 1994; Weight and

Sonderegger 2000). Additionally, the hydraulic conductivity of samples may be

obtained from laboratory measurements via permeameters. Permeameters enable

water to move through the sample and the flux is measured to estimate hydraulic

15

conductivity. However, both grain-size analysis and laboratory testing require the

removal of samples from field conditions. Removal of a sample may disturb

sediment packing leading to error within the estimated hydraulic conductivity. In

situ hydraulic testing to determine aquifer properties therefore often results in more

accurate estimates. In situ hydraulic testing is often performed via bailer or slug tests

and pumping tests.

2.4.5 Aquifer heterogeneity

Very few, if any, coastal barriers are completely homogenous and isotropic (Harris

1967), and aquifer heterogeneity within sand islands has a profound affect on

groundwater occurrence and movement through the island. Lateral or vertical

variations in hydraulic properties and the presence of low permeability layers at

depth have been shown to cause deviations of the freshwater lens from the idealised

DGH morphology (Ruppel et al. 2000).

Layers of less permeable sediment can restrict or prohibit the infiltration of water

through the unsaturated zone, and cause water to accumulate on top of these layers

(Fetter 1994). Elevated groundwater tables that exist above layers of less permeable

units are termed perched water tables (Driscoll 2003). The presence of low

permeable material affecting the groundwater regime of barrier environments is not

uncommon (e.g. Harris 1967; Bolyard et al. 1979; Vacher 1988; Burkett 1996;

Harbison 1998; Collins and Easley 1999; Anderson et al. 2000; Ruppel et al. 2000).

Perched groundwater moves laterally above the low permeability layer and may

either seep downward toward the main water table at the layers margin or is

discharged at the coastal boundary.

Additionally, where the lens is perched on shallow, low permeable material, water

tables are often higher than they would be if the material were not present (Vacher

1988). Figure 6 illustrates the response of the freshwater lens to low permeability

material at a shallow depth within the sedimentary profile of a sand island.

16

Figure 6. Fresh groundwater flow through a barrier island composed of stratified sediments of

different permeability, where hf = the head of freshwater above mean sea level and Z is the depth of

the truncated freshwater lens (after Harris 1967)

As a well studied example, Hatteras Island, North Carolina, USA, contains

heterogeneous stratigraphy resulting in elevated water levels across the island (Harris

1967; Burkett 1996; Anderson et al. 2000). Field data consisting of cross-island

water table trends indicate unusually high water table elevations that are related to a

shallow low permeability unit (Anderson et al. 2000). The low permeability unit was

interpreted as a former wetland that has been buried by a series of parabolic dunes.

Hydraulic tests on Hatteras Island by Burkett (1996) consisted of several multiple

well pumping tests that identified the aquifer to behave as a stratified aquifer. The

conceptual model of the island is similar to that illustrated in Figure 6, with an upper

unconfined aquifer, a deep semi-confined aquifer, and a low permeability layer

separating the two aquifers. Such a model is of significance to Bribie Island.

Burkett (1996) attained values for the hydraulic properties of transmissivity,

horizontal hydraulic conductivity, vertical hydraulic conductivity, and specific yield

for the upper unconfined aquifer. Following from the studies of Burkett (1996),

numerical modelling of the cross-island water levels by Anderson et al. (2000)

provided values of horizontal hydraulic conductivity for the deeper sediments and the

low permeability unit of the stratified island aquifer. The analysis of Anderson et al.

(2000) confirmed that the low permeability unit caused the elevation of the water

table and that the layer provided some confinement of the deeper aquifer.

17

Additionally, aquifer heterogeneity can also impact on the groundwater chemistry of

the island aquifer. Fresh groundwater typically flushes saline water from permeable

zones more rapidly than from low permeable zones. For the case of Hatteras Island,

differential flushing of saltwater water through the stratified permeable and relatively

impermeable sediments has lead to more than one freshwater/saltwater water

interface in the vertical section (Harris 1967). Therefore, the position of the interface

is not governed by the DGH principle or by any of the modifications to this

relationship that assume lithologic homogeneity.

Variable freshwater/saltwater water interface relationships have also been reported

for other barrier islands where aquifer heterogeneity is prominent. The island

aquifers of Grand Isle, Louisiana, USA, and Assateague Island, Maryland, Virginia,

USA, are other examples where variations in hydraulic conductivity and permeability

exist (Bolyard et al. 1979; Collins and Easley 1999).

2.4.6 Hydrochemistry

Results from geochemical studies of groundwater within barrier environments also

indicate that aquifer heterogeneity not only affects the freshwater/saltwater water

interface but can also affect major and minor ionic relationships (Laycock 1975;

Reeve et al. 1985; Collins and Easley 1999; Suresh Babu et al. 2002). Evaporative

processes typically result in an atmospheric supply of ions that reflect ionic ratios of

local seawater. Since groundwater recharge in an island setting is dominated by

rainfall, the resulting groundwater chemistry may also resemble local seawater ionic

ratios. In addition, a low relief sand island such as Bribie Island is highly susceptible

to salt spray and surface water chemistry (ionic ratios) may reflect seawater for this

region (at least partially). Deviation of groundwater ionic ratios from the initial

rainfall chemistry is largely the result of interaction between groundwater and the

island sediment.

For a barrier island, the dominance of an almost entirely silicious dune complex may

result in only minor dissolution of minerals due to the limited degree of weathering.

Enrichment of silica in the groundwater body is typically the most common product

of these weathering processes and serves as a useful indicator of flow path length

18

(Little and Roberts 1982). However, sodium, magnesium, calcium, chloride,

bicarbonate and pH can also be used to discriminate between different water types

that have been exposed to different aquifer materials. Where the aquifer includes

organic rich indurated sand the water chemistry may show signs of ion exchange and

the dissolution of minerals resulting in a groundwater of reduced pH and altered

ionic ratios (Reeve et al. 1985).

As an example, recent hydrogeochemical analysis of groundwater samples from

Valadares Island, Brazil, typically display a chemical signature of sodium,

potassium, and chloride that indicate rainfall as the dominant recharge source

(Suresh Babu 2002). However, the relative enrichment of sodium and the

substantially lower amounts of magnesium and calcium were attributed to the high

concentrations of organic carbon in the water table aquifer. Elevated concentrations

of organic carbon within groundwater samples from numerous coastal barrier

environments have often been associated with low permeability layers (Laycock

1975; Pye 1982; Reeve et al. 1985; Harbison 1998; Anderson et al. 2002). Indurated

podsol layers are a common feature of many coastal areas around the world and

particularly along the Australian eastern coastline. Where drainage is low, such as

that on beach ridge plains, areas of humate deposition may cover wide areas (Pye

1982).

2.5 Nature of Indurated Sand

Humic substances are readily available in highly vegetated coastal areas. Soluble

and colloidal humic substances form as a result of bacterial breakdown of organic

matter and subsequent leaching of humus by rainwater (Pye 1982). The soluble and

colloidal humic substances are rapidly eluviated from the vadose zone and deposited

as cutans on quartz grains (Cox et al. 2002); the resulting layer of dark brown to

black indurated sand is referred to locally as “coffee rock”. However, Pye (1982)

suggests “humicrete” as a more suitably descriptive term for the largely humate-

cemented sediments. Indurated sand has been classified as quartz sand grains

cemented together by the infilling of pores by a variety of cements, predominately

organic matter and clays (Farmer et al. 1983; Thompson et al. 1996; Cox et al. 2002).

19

Humate tends to remain soluble under alkaline conditions and to flocculate where pH

is acidic (Pye 1982). Flocculation has been reported to occur at pH 4.5 and lower,

although, Pye (1982) noted that flocculation of the Cape Flattery, north Queensland,

humate only occurred at pH ≤ 2 and suggested that pH variation is unlikely to be the

major control of humate precipitation. Additionally, since surface water and shallow

groundwater of many coastal sand bodies often have an average pH > 2, it is also

suggested that the prevailing acidic conditions are not the sole source of humate

precipitation.

Therefore, the dominant mechanism for the deposition of humate material in barrier

environments is likely to be mechanical. It is suggested that the repeated flushing of

fresh humate into the sands and the subsequent drying during low rainfall seasons

leads to thickening of cutans and infilling of void spaces (Pye 1982). In some cases

the intergranular space of these sediments is completely filled by humate,

dramatically reducing porosity and permeability (Thompson et al. 1996). This

wetting and drying process is considered integral to the formation of the indurated

layers and is considered to occur typically beneath drained beach ridges. For

example, in areas that remain waterlogged such as the swale areas of barrier coasts,

the absence of the drying phase may only result in very friable organic rich sands and

not highly indurated sand layers.

The elevation of groundwater above indurated sand layers is a common occurrence

due to reduced porosity of the sands. As a consequence streams and lakes associated

with indurated sand layers are commonly formed at higher than normal elevations.

An example of these perched lakes occur within the large quaternary sand masses of

the southeast Queensland coastline, including Fraser Island, Moreton Island, North

Stradbroke Island, and the Cooloola sand mass (Laycock 1975; Little and Roberts

1983; Reeve et al. 1985).

The Cooloola sandmass contains a prominent example of indurated sand

development beneath the sand dunes. The Cooloola National Park and Forestry

Reserve is approximately 100 km north of Bribie Island and consists of a massive

episodic transgressive barrier complex. The sand dunes are dominantly quartz sands

that reach elevations of 260 m above sea level. The sands are highly permeable and

20

the sandmass forms a large unconfined aquifer. Reeve et al. (1985) examined the

chemical composition of waters from springs, creeks and lakes throughout the

Cooloola area as part of a study of landscape dynamics in coastal sand dunes.

Numerous lakes and streams occur at elevated levels above the regional water table

and are considered to be perched above low permeability layers of indurated sand.

These layers are associated with older dune systems (Reeve et al. 1985). The

perched water is usually stained with organic matter (“black water”), where as the

water emanating from the deep-seated main water table is colourless (“white water”).

The organic rich perched water is also distinguished by lower concentrations of

silica, and pH; additionally, higher concentrations of tritium indicate a shorter

residence time than waters of the main storage system (Reeve et al. 1985).

Similarly, Laycock (1975) noted discernable differences between the water

chemistry associated with indurated sand layers and water chemistry of the regional

water table within North Stradbroke Island, southeast Queensland. Like the

Cooloola sandmass, North Stradbroke Island is also classified as an episodic

transgressive barrier. Geophysical investigations on North Stradbroke Island

revealed a number of areas where indurated sand layers displayed a seismic velocity

higher than the surrounding sandy units. This seismic reversal was thought to be due

to the relatively impermeable nature of the indurated sand layer above which there

was an observed saturated zone. This was considered to indicate an area of a

perched water table (Laycock 1975). Surprisingly, the influence of indurated sand

on the regional groundwater regime may in fact be quite localised for large systems

such as North Stradbroke Island and the Cooloola sandmass. However, for smaller

groundwater regimes, the influence of this type of aquifer heterogeneity may be a

dominant feature of the island environment. The following study is focused on the

influence of these heterogeneities on the groundwater regime of Bribie Island.

21

3.0 PHYSICAL SETTING OF BRIBIE ISLAND

3.1 Regional Setting

Bribie Island is located within northern Moreton Bay, southeast Queensland and is

separated from the mainland coastline by the shallow tidal estuary of Pumicestone

Passage (Figure 7). The island is situated approximately 65 km north of the capital

city, Brisbane, has an approximate area of 144 km2, length of 30 km and an average

width of 5 km.

Figure 7. Location of Bribie Island in Moreton Bay, Queensland, Australia. Outer islands which form

Moreton Bay are also shown

Figure 8 illustrates that urban development is restricted to the southern one-third of

Bribie Island, which is a popular retirement and tourist location with a rapidly

growing permanent population. The current population is approximately 15 000 but

22

during summer holiday periods the population of the island can increase by up to

three times (Harbison and Cox 1998). The island is additionally the location of a

weather research station, an aquaculture research station, a water supply reserve,

national park areas, and commercial pine plantations. Road systems in the northern

two thirds of the island are unsealed forestry tracks only.

Figure 8. Geographical map of Bribie Island indicating drainage features, surface water bodies,

residential areas, forestry tracks, and the adjacent mainland (GIS data sourced from NRM & E)

Bribie Island has a landscape more similar to the adjacent coastal lowlands than to

the massive transgressive outer islands of Moreton and North Stradbroke (Coaldrake

1961). A significant proportion of the island is less than 5 m above sea level and the

maximum elevation is 17 m above sea level. North-northwest trending dune ridges

halla

This figure is not available online. Please consult the hardcopy thesis available from the QUT Library

23

(relict foredunes) occur as the dominant topographical features and form the highest

point in the central-eastern section of the island. Figure 9 illustrates that two beach

ridge systems are separated by a large swale (interconnected low-lying Melaleuca

swamp system) extending through the long axis of the island. The central swale is a

relict estuary and is the dominant drainage feature of the island. Surface water

drainage across the island is not well developed due to rapid infiltration through

transmissive surface sands and the low relief of the island. In the south of the island

the natural drainage is via wetlands to Dux and Wright’s Creek, both of which are

now modified. In the north the Central Swale discharges into Westaway Creek. A

series of fresh and brackish lagoons fringe the east coast.

Figure 9. Bribie Island topographical map indicating drainage features, surface water bodies, and two

dominant north-northwest trending dune ridge systems (GIS data sourced from NRM & E)

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3.2 Geology

Bribie Island is composed of Pleistocene to Holocene sand to clayey-sand deposits

overlying bedrock of Jurassic Landsborough Sandstone as illustrated in Figure 10.

The Landsborough Sandstone is predominantly fine-grained quartzose sandstone.

The sandstone contains shale beds, is underlain by a conglomerate base and is in

excess of 100 m thick (Ishaq 1980). Sandstone does not crop out on Bribie Island.

Depth to bedrock is confirmed by drilling.

Figure 10. Generalised geological map of Bribie Island indicating the predominance of Holocene to

Pleistocene unconsolidated material overlying Jurassic Sandstone (GIS data sourced from NRM & E)

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25

During long periods of lower sea level the surface of the sandstone bedrock was

weathered and eroded before deposition of the Bribie Island sand sequences. The

weathered profile of the sandstone bedrock on the mainland can vary in thickness

from several metres to 20 m thick and exhibits laterite zonation (Oberhardt 2000;

Ezzy et al. 2002). Previous studies on the adjacent mainland indicate the sandstone

provides a limited resource of groundwater (Cox et al. 1996). Limited data exists

relating to the weathered sandstone beneath Bribie Island. However, it is inferred

that the weathered sandstone beneath the unconsolidated sediments of Bribie Island

is of limited groundwater resources as per the mainland.

A palaeochannel within the sandstone bedrock extends from the mainland (Ezzy

2000; Oberhardt 2000) continuing northeast under Bribie Island as illustrated in

Figure 11. This bedrock low is confirmed by drillhole data (Harbison 1998). The

sediment profile is thickest in the vicinity of the palaeochannel with depths > 40 m.

Figure 11. Aquifer base contour map of Bribie Island from drillhole data (after Harbison 1998).

Geographical features are also indicated

26

3.3 Geomorphology

The unconsolidated deposits result from sea level variations during the Pleistocene

and Holocene (Coaldrake 1960; Lumsden 1964). The island has been formed by the

deposition of sand supplied by the net northward movement of sands along the

mainland coastline by the process of longshore drift (Isaacs and Walker 1983). The

shallow sand profiles are typically comprised of well-sorted, reworked, fine to

medium-grained sands (Harbison 1998), and are thinnest towards the north west of

the island as illustrated in Figure 11.

The stratigraphic successions of Quaternary sand deposits of Bribie Island comprise

four main units (Lumsden 1964; Hekel and Day 1976; Ishaq 1980; Harbison 1998):

1. Pleistocene beach ridge system

2. Holocene beach ridge system

3. active foredune system

4. estuarine tidal delta system

3.3.1 Pleistocene beach ridge system

The Pleistocene beach ridge sands constitute the most widespread unit within the

island and consist of fine to medium quartz sand. Features such as the multiple

beach ridges and parallel foredunes as illustrated in Figure 12 are related solely to

progradation (Coaldrake 1960; Lumsden 1964; Pye and Bowman 1984). Prior to

erosion, these ridges were “hinged” at a headland east of Caloundra Head and

followed a gradual concave sweep to the south (Harbison 1998). The longitudinal

axes of these ridges are aligned parallel with the prevailing southeast winds that can

be readily seen in aerial photographs. The total thickness of the Pleistocene

sediments varies from 5 to 25 m, and they dip gently to the south and east beneath

the Holocene beach ridge sediments (Ishaq 1980).

Within the Pleistocene dune sands exists an extensive indurated sand layer at an

approximate depth of 5-6 m with a maximum measured thickness of 9 m (Ishaq

1980). The indurated sand layer has good correlation between drill holes. Harbison

(1998) graphically displayed the occurrence and thickness of the indurated sand layer

27

across the island (Figure 13), the indurated layer at its thickest is approximately 5-8

m thick, but over much of the island the thickness is 1-3 m.

Figure 12. Lithological map of Bribie Island indicating the four major types of geomorphology;

Pleistocene beach ridges, Holocene beach ridges, active foredunes, and estuarine tidal delta deposits

(GIS data sourced from NRM & E)

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28

The greatest thickness of indurated sand is located centrally on the island beneath the

main beach ridge system. Based on existing drill hole data the degree of induration

decreases with depth to a zone of dark brown stained sands. Indurated sand is

uncommon in the Holocene beach ridges south of the Woorim – Bongaree road and

in the tidal delta areas (Harbison 1998). The top of indurated sand layer is generally

1-3 m above mean sea level.

Analysis of samples from Bribie Island using Scanning Electron Microscopy (SEM)

has revealed the presence of cutans infilling the pores, suggesting that cementation is

mainly by organic material (Harbison 1998). Results from Loss On Ignition (LOI)

analysis of Bribie Island indurated sand samples indicate a range of organic carbon

concentrations of 2.3 - 7.7 % (n=11) with an average of 4 % (Harbison 1998; Cox et

al. 2002).

Figure 13. Thickness of indurated sand layer for Bribie Island based on drillhole data (after Harbison

1998)

29

3.3.2 Holocene beach ridge system

Holocene beach ridge sands occupy the southernmost part of Bribie Island. These

sands consist of well-sorted quartz sand with shell rich fragments (Ishaq 1980). The

beach ridges display varying alignments (Figure 11) that are most likely due to a

change in recent marine current patterns within Moreton Bay (Armstrong 1990;

Harbison 1998). These sediments display the ridge swale morphology similar to the

older Pleistocene ridges. It is not possible to determine the boundary of younger and

older sand deposits with any accuracy, because of the similarity in lithology and

absence of a marker horizon (Ishaq 1980). Additionally, recent accretion of beach

ridges in the south of the island is suggested to have occurred concurrently with

erosion of the active foredune further to the north. Along the east coast of Bribie

Island the ocean current trend is to the south, leading to the movement of eroded

sediment in this direction. The southerly ocean current is in opposition to the

northward longshore currents that dominate the rest of the regional coastline. The

change in current direction is the result of refraction of northward moving longshore

currents around the headland of Moreton Island (Jones 1992; Lester 2000).

3.3.3 Active foredune system

The active foredunes are typically between 5-10 m in height and occur as a narrow

strip along the eastern coastline, as illustrated in Figure 9. Most of these dunes are

stabilised by full vegetation. However, erosion is occurring along this section of the

coastline creating erosion scarps (Jones 1992). Four large coastal lagoons are

situated immediately behind the active foredunes. The active foredune system

extends to the north and forms a narrow spit. The spit can experience severe erosion

leading to a possible future breakthrough (Lester 2000).

3.3.4 Estuarine tidal delta system

Estuarine sediments predominately occur on the western part of Bribie Island (Figure

12) and are composed of sands and mud deposited in low energy bay and lagoonal

environments (Hekel and Day 1976; Ishaq 1980). The estuarine deposits occur

within the central swale between beach ridge deposits and in the tidal delta system

(Harbison 1998). The central swale is suggested to have in-filled during the last

6000 years, initially from the south. Deltaic deposits are derived from local lithic

30

sources and marine sources; they consist of low-lying poorly sorted sediments and

occur in the north and west of the island (Harbison 1998).

3.4 Drainage System

The drainage patterns of Bribie Island are ill-defined; however surface water exists in

the form of highly ephemeral streams, marshy swales, and coastal lagoons. Most

significant surface water flow occurs on the island notably after heavy rainfall

periods. Additionally, significant flow of surface water occurs after heavy rainfall

periods from the beach ridges towards the central swale and the coastal lagoons.

Ponded water is often held in depressions where an organic silt seal often restricts the

infiltration of surface water for days to weeks after a heavy rainfall event (Harbison

1998).

3.5 Climate

Bribie Island has a sub-tropical climate typical of coastal southeast Queensland with

mean monthly maximum temperatures ranging from 20 oC to 29 oC. Currently there

are no rainfall stations on Bribie Island registered with the Bureau of Meteorology.

However, previous records from two abandoned registered stations in the south of the

island give an annual rainfall amount of approximately 1350 mm (Isaacs and Walker

1983; Harbison 1998). Annual and monthly rainfall statistics are shown in Tables 3

and 4 respectively for the period of registered operation (Isaacs and Walker 1983).

Table 3. Annual rainfall from registered stations located on Bribie Island (after Werner 1998)

Station Number and

Location

040697

Redcliffe

SES

040027

Bribie Is.

(Bongaree)

040685

Bribie Is.

(UQ)

040284

Beerburrum

040040

Caloundra

SS

Period 1981-1997 1931-1990 1978-1993 1898-2003 1899-1992

Average annual

rainfall (mm/yr) 1179 1358 1287 1444 1560

Maximum annual

rainfall (mm/yr) 1530 (1983) 2471 (1974) 1639 (1988) 2802 (1974) 2560 (1974)

Minimum annual

rainfall (mm/yr) 721 (1993) 726 (1944) 940 (1979) 407 (1902) 726 (1902)

31

Table 4. Mean monthly rainfall – Bongaree (after Isaacs and Walker 1983)

Month J F M A M J J A S O N D

Mean (mm) 173 190 178 108 105 84 70 49 46 102 103 132

In addition to rainfall stations, an isolated tipping-bucket rainfall gauge is situated on

the central eastern coastline. The rainfall gauge is operated by the Queensland

Department of Natural Resources, Mines and Energy and records values of rainfall

that approximate 1400 mm per year (Harbison 1998). The wettest months are the

summer period of December to March, and the winter is comparatively dry as

illustrated in Figure 14. Summer cyclonic conditions are also occasional. There is

an increase in annual rainfall in a northerly direction along the island of 20% as a

result of rain shadow effects from the two large outer islands, Moreton Island and

North Stradbroke Island (Harbison 1998).

Figure 14. Rainfall data for Bribie Island years 1993 to 2000. Data provided by the tipping bucket

rainfall gauge operated by the Queensland Department of Natural Resources, Mines and Energy No.

540055

3.6 Evaporation

No evaporation data are published for Bribie Island. The nearest evaporation station

is located at the Brisbane Airport approximately 60 km to the south. Results from a

class A pan (Table 5) show the variation in evaporation during the year (Isaacs and

32

Walker 1983). These records indicate the mean annual evaporation at Brisbane is

approximately 1570 mm.

Table 5. Mean monthly evaporation – Brisbane (after Isaacs and Walker 1983)

Month J F M A M J J A S O N D

Mean (mm) 180 142 142 117 83 66 72 100 131 157 176 202

Av. daily (mm/d) 5.8 5.1 4.6 3.9 2.7 2.2 2.3 3.2 4.4 5.1 5.9 6.5

Typical of coastal southeast Queensland, evaporation slightly exceeds mean annual

rainfall. Additionally, Harbison (1998) indicates that potential evapotranspiration for

Bribie Island for the period 1990-1995 has daily ranges between 17 mm and 1 mm

per day, with an average day-to-day variation of 2 mm. The average annual potential

evapotranspiration for the same period is 1770 mm/year (Harbison 1998); of note

Bubb and Croton (2002) suggest that for the pine plantation evapotranspiration rates

approximate 1100 mm/yr.

3.7 Groundwater Recharge

Harbison (1998) indicates that a comparison of rainfall amounts with monitoring

well water levels indicates that four general situations occur, which have been

quantified by correlation of hydrographs with mean cumulative rainfall. The four

situations are summarised as follows:

a) recharge is well-correlated with rainfall, which is typical of well-drained

Holocene ridges (e.g. the area south of the Woorim-Bongaree Road);

b) recharge is poorly-correlated with rainfall (i.e. the water table “under-

responds’ to rainfall events). This situation is found in deeper boreholes in

Pleistocene sand deposits overlain by indurated sand layers.

c) recharge “over-responds” to rainfall. This is typical of swales where

recharge has been laterally directed from topographically higher areas,

either as surface runoff or as shallow seepage across indurated sand layers;

and

d) recharge and rainfall are poorly-correlated, but there are large hydrograph

fluctuations. These fluctuations are common in areas under strong tidal

influence.

33

Water levels in bores in the southern part of the island are also subject to

anthropogenic influences, such as injection and extraction of water for irrigation and

domestic uses. These factors can complicate natural discharge and tidal effects.

After rainfall, recharge to the regional water table generally occurs within 48 hours,

which allows the response to be studied at spatially discrete points. Harbison (1998)

estimated recharge (using the chloride accretion method) at 7% for the island as a

whole and 18% for the southern part of the island respectively. Previous estimates of

recharge to the southern part of the Bribie Island are 40-45% (Lumsden 1964) and

18% (Ishaq 1980). A previous estimate for the whole of island based on numerical

modelling is 8% (DNR 1996).

3.8 Vegetation

Pine plantation has replaced large tracts of native vegetation across the central two

thirds of the island. The pines are restricted predominantly to the two dune systems

leaving native Melaleuca woodland to dominate the adjacent swales and coastal

zones. Vegetation types in the less-disturbed areas on the island are related to soil

water availability, soil nutrient status, salinity, waterlogging tolerance and landform

age (Harbison and Cox 1998). As a result, zonation of vegetation communities and

species can also serve as useful indicators of shallow groundwater occurrence

(Harbison 1998).

3.9 Land use

The northern two thirds of Bribie Island is under the management of the Queensland

Parks and Wildlife (QPW) organisation. However, the Queensland Department of

Primary Industries – Forestry (DPI-Forestry), uses the majority of this area under

special lease for the growth of pine plantations. Commercial pine plantations have

been in service on Bribie Island since 1960 when Australian Paper Manufactures

(APM) planted the first rotation. During the first rotation the pines suffered greatly

from high stocking rates, minimal thinning, insect attack, drought and fire.

Ownership of the plantation changed from APM to CSR Softwoods before DPI-

Forestry took over the operation. Removal of the first rotation was finalised at the

end of 2002 while planting of the second rotation occurred concurrently.

34

Remnant vegetation is mostly secured as National Park. The National Park area

includes the entire northern spit, the active foredune of the east coast, the deltaic and

tidal areas of the western coastline, and the area south of the pine plantation.

Additionally, corridors through the plantation have been established to help minimise

impact on fauna movement throughout the island. The remnant vegetation of the

central swale is currently under the control of the Queensland Department of Natural

Resources and Mines (NRM & E).

35

4.0 HYDROGEOLOGICAL STUDIES OF BRIBIE

ISLAND

Since the opening of the Bribie Bridge in 1963, large urban expansion on the island

has placed high demands on the potable water supply. Supply of potable water to the

growing urban population on the island has been the priority of most groundwater

investigations over the last four decades. The investigations have been almost

entirely concentrated in the younger Holocene sands in the south of the island

adjacent to the residential areas.

Groundwater management on the island was initiated in 1963. At the request of the

Department of Local Government, the Geological Survey of Queensland (GSQ)

carried out drilling of 31 wells at an average depth of 14 m (Lumsden 1964). An

area of 2.6 km2 was proposed and set aside as a water reserve south of the cross-

island road (Figure 15), this being considered the deepest part of the aquifer. Of the

thirty-one wells, 3 were abandoned, 6 were established as extraction wells, 16

observation wells were placed along an east-west transect, and 6 observation wells

were placed adjacent to the coastline. Further investigations in 1966-1967, included

the drilling of an additional 21 extraction wells within the water reserve to

supplement the existing system.

After continuing problems with the extraction wells due to iron fouling of the

screens, groundwater extraction was converted in 1971 to a 3 km long and 5 m deep

extraction trench located within the water reserve. John Wilson and Partners (1979)

reviewed the performance of the water reserve, trench system, pumping plant, and

the treatment processes. It was recommended that the water reserve be expanded to

the west and north and the trench system be fully developed. The existing trench

system was extended and a second trench north of the cross-island road was

constructed. Both trenches were also subsequently deepened.

A hydrogeological reconnaissance of the southern part of the island was undertaken a

second time by GSQ in 1980 (Ishaq 1980). The investigation considered the further

expansion of the water reserves particularly south of the cross-island road (Figure

15). However, two other areas north of the cross-island road were also noted for

36

future consideration, the eastern coastal strip, and the area south of the pine

plantation. Additional to field observation of water levels and water balance

calculations, Ishaq (1980) analysed two pumping tests conducted by John Wilson

and Partners in 1966. The pumping tests were designed to give estimates of aquifer

parameters such as hydraulic conductivity and aquifer specific storage.

Groundwater modelling of the southern section of the island was initiated with a two-

dimensional dynamic model (cross-sectional) to determine the response of the saline

groundwater interface adjacent to the main water extraction trench (Isaacs 1983). To

further develop the modelling process a finite difference numerical model (horizontal

planar) of the same area was developed (Isaacs and Walker 1983). Both of these

models worked from assumed hydraulic parameters and indicated that the

groundwater heads should be raised between the extraction trench and the adjacent

sea. The relocation of the effluent recharge beds to the southeast of the island was

recommended to artificially increase the groundwater heads. The effects of effluent

recharge, the fate of the recharged effluent, and the rate of change of water quality

was investigated by Marsalek and Isaacs (1988).

The first whole-of-island hydrogeological investigation was initiated by the Water

Resources Commission in 1992 and included the drilling of 23 observation wells

along 7 cross-island transects from the north (adjacent to Westaway Creek) to the

southern coastline as shown in Figure 15 (Department of Environment and Heritage

1993). Since 1992 regular monitoring of groundwater levels and chemistry from the

extensive observation well network has been conducted and results have been stored

within the NRM & E groundwater database. Additionally, two wells were fitted with

continuous groundwater level logging devices and a rainfall gauge installed on the

eastern coast beside one of the automated wells. To further the whole-of-island

investigation, the Groundwater Assessment Group of NRM & E installed 6

additional observation wells across the island in 1995. From the observed

groundwater levels a transient finite-difference numerical model was developed

(Werner 1998). The model was designed to support management of the pine

plantation clear-felling operation.

37

A similar process was also undertaken in 1998 where a transient finite-difference

groundwater model was developed to investigate processes involved with the

development of an extraction well field along the axis of the Pleistocene beach ridge

in the north of the island (Werner 1998). The model incorporated varying recharge

rates, hydraulic parameters and extraction rates. However, a limiting factor for the

model was that the elevated water table was not included in the model nor was there

consideration for low permeability areas. Hence the model found difficulty in

achieving calibrated results.

Harbison (1998) also conducted an integrated study of the hydrogeology for the

whole of Bribie Island with a goal of developing a conceptual groundwater model.

Cross-sections across the existing DNRM & E transects A-G are included within the

DNR (1996 unpublished) report. These transects were evaluated by Harbison (1998)

to develop a conceptual model of Bribie Island. The groundwater regime of the

island was defined in terms of geology, water level fluctuations, response to rainfall

and geochemistry. Additionally, aquifer hydraulic properties were also attained

through laboratory hydraulic testing. Harbison (1998) noted that the critical factors

in the behaviour of the groundwater system are the elevation of the seawater

boundary, the extent of low permeability layers and the degree of aquifer

heterogeneity predominantly in the form of indurated sand layers.

The following study continues the investigation of the hydrogeological regime of

Bribie Island. This study is focused on transect D-D’ across the middle of the island.

This transect is referred to as the “reference transect” within the remainder of this

study. In situ testing of the Bribie Island sand mass across the reference transect has

been designed to quantify the hydraulic properties of the island aquifers. This data is

required for further development of the conceptual groundwater model.

38

Figure 15. Previous monitoring well locations, transect lines, drainage features and surface water

bodies

39

5.0 METHODS

A number of standard techniques for the assessment of physical and chemical

properties of aquifer materials, water chemical character and determination of in situ

permeability of the sand mass were applied. Prior to this testing a groundwater well

drilling program was designed and implemented. The overall approach taken can be

subdivided into three parts:

a) Drilling and hydraulic testing

All existing data including monitoring wells locations and water level

records were collated before hydraulic testing was performed. A

comprehensive drilling program was undertaken to expand the monitoring

well network and test the sand mass at different depths. The well network

enabled time-series monitoring of groundwater levels and the

performance of hydraulic testing.

b) Water and sediment sampling

Each drill hole was progressively logged during drilling and samples were

taken at intervals of interest for laboratory analysis. Selected sediment

samples were also collected for age dating analysis. Groundwater

samples were collected from the monitoring well network for testing of

field physico-chemical properties and for total ion chemical analysis.

c) Data analysis

Hydraulic test data were analysed by analytical methods to gain estimates

of hydraulic conductivity and specific storage across the reference

transect. Age dating of sediment samples by the optically stimulated

luminescence (OSL) method was also performed to identify trends in

island evolution and island stratigraphy. Both groundwater and surface

water samples were analysed geochemically for chemical type and ionic

ratios.

40

5.1 Drilling and Hydraulic Testing

It is possible to determine in situ hydraulic conductivity and specific storage values

of a formation by means of tests carried out in monitoring wells. These tests

typically involve the measurement of the water level around one or more monitoring

wells during which the water level is raised or lowered. An array of monitoring

wells were designed to monitor water levels from various levels within the

formation.

5.1.1 Drilling program

Twenty-one groundwater monitoring wells were installed in March 2001 along two

transects across the middle of Bribie Island. The new monitoring wells are

sequentially numbered from 14100131 – 14100151 and their locations are illustrated

in Figure 16. The numbering system compliments the existing Queensland

Department of Natural Resources and Mines (NRM & E) groundwater monitoring

well identification system. The prefix of 14100 will be omitted here for brevity.

The new drill holes were constructed using the rotary mud drilling method. 150 mm

holes were drilled through the unconsolidated sand profile using a wash bore blade

bit. The rotary mud drilling method is considered the most appropriate for

unconsolidated material particularly for dune sand such as the Bribie Island aquifers

(Land and Water Biodiversity Committee 2003). The rotary mud drilling method

relies on the injection of drilling mud/water slurry to support the drill hole and to

carry the cuttings to the surface. However, a consequence of injecting water into the

drill hole is the contamination of the formation with drilling fluid. Well development

necessitates the removal of the injected water before reliable groundwater levels and

groundwater chemistry can be recorded. The removal of the drilling water is

typically achieved by high volume pumping from the well. All drilling fluids were

removed from each well before water levels and water chemistry monitoring.

Sediment samples from the drill holes were collected from 0.5 m intervals and at

changes in lithology. Standard Penetration Tests (SPT) were also conducted to

measure the resistance of various sediment units to penetration, particularly those

units suspected of acting as semi-confining layers.

41

Figure 16. Location of groundwater monitoring wells (n=21) constructed during this program.

Existing monitoring wells of NRM & E (n=16) and HLA (n=14) are also shown. All QUT and NRM

& E monitoring well identifications are prefixed with 14100

42

SPT tests were conducted at sections of interest, particularly where indurated sand

was encountered. A “splitspoon” sampler was attached to the bottom of a core barrel

and lowered into position at the bottom of the drill hole. The sampler was driven

into the formation by a drop hammer weighing 68 kg falling through a height of 0.76

m. The number of hammer blows required to drive the sampler three successive 150

mm increments (total of 450 mm) were recorded. The SPT N value, an indication of

the formation stiffness, is the number of blows required to achieve penetration from

150-450 mm. For all holes that penetrated through the indurated sand layer, rotary

drilling was continued to the weathered sandstone bedrock. At the bottom of the drill

hole an SPT sample of weathered sandstone was collected to confirm the lithology

change. Each drill hole was progressively logged as drilling continued; geological

logs are presented in appendix D.

5.1.2 Well construction

Groundwater monitoring wells are typically of small diameter and are equipped for

the purpose of taking groundwater samples and the monitoring of water levels. All

newly constructed groundwater monitoring wells on Bribie Island were constructed

to the requirements set by the Land and Water Biodiversity Committee (2003).

A detailed transect of the island is provided by NRM & E transect (D-D′) Figure 16.

Sixteen of the new wells were established on the D-D' transect that is now comprised

of twenty-three monitoring wells. The D-D′ transect is referred to as the “reference

transect”. The reference transect is comprised of 8 nested monitoring well sites, and

at these sites, multiple monitoring wells are slotted at different intervals. The types

of wells along the transect and their positions within the profile of the island are

summarised in Table 6.

Table 6. Well type and slotted casing lengths of monitoring wells across the reference transect

Type of well Slot interval Number of wells

Shallow - slotted above indurated sand 1 – 5 m 10

Intermediate - slotted within indurated sand 7 – 10 m 2

Deep - slotted beneath indurated sand 15 – 35 m 11

43

Five shallow monitoring wells (1-5 m depth) were also developed to the immediate

south of the reference transect to further confirm aquifer character below the eastern

dune system. The five shallow monitoring wells compliment the existing network of

privately owned monitoring wells located to the west of the transect. The privately

owned wells have been developed by the Pacific Harbour residential development

and are situated within an area designated as a future golf course. The environmental

consultancy group, HLA-Envirosciences Pty Limited, currently monitors the golf

course monitoring wells. These wells will be referred to as HLA monitoring wells

with the identification system of: 1s (monitoring well number one – shallow 1-5 m

depth) to 8d (monitoring well number eight 8 – deep 20-30 m depth).

The monitoring wells were cased with 50 mm diameter class 12 PVC (Figure 17) and

consist of 3 m lengths and joined by end threads. The machine slotted casing used

for the monitoring wells consisted of the same material as the casing. The slotted

casing also provides support for the formation material and retains openings into the

sand formation. Filter packing around the slotted casing with 3 mm diameter quartz

gravel provides additional support to the formation whilst increasing the effective

diameter of the well. Efficiency and specific capacity of the well is increased as a

result of the larger effective diameter of the well. Bentonite grouting with a

thickness of at least 0.5 m above the slotted casing prevents lateral leakage.

The head works of the monitoring wells consists of standard NRM & E lockable

galvanised steel protective collars. The bases of the collars were set in concrete and

marker posts have also been used to increase visibility. Most monitoring wells have

been located adjacent to forestry track intersections to also increase the visibility of

the wells: and the likelihood the wells will not be destroyed by working forestry

equipment. Monitoring well identification numbers have been listed on the PVC end

cap. Following construction, each bore was surveyed to an accuracy of within ± 5

mm horizontally above Mean Sea Level.

Monitoring well survey heights were calibrated against the existing network of NRM

& E monitoring wells. Monitoring well heights above sea level were measured using

Leico automatic level survey equipment, and the wells located using Global

Positioning system (GPS).

44

Figure 17. Typical construction method for monitoring wells installed during the 2001 drilling

program

45

5.1.3 Water level monitoring

Monitoring of groundwater levels across Bribie Island has been conducted on a

regular basis since the development of the NRM & E monitoring well network in

1992. Previous records are archived within the NRM & E groundwater database.

Throughout this current study, monitoring of the expanded well network for

groundwater levels occurred between August 2000 and June 2002 at the average

interval of 1 month. The monitoring of approximately 50 wells included: 16 NRM &

E wells, 14 HLA wells and 21 newly constructed wells. Groundwater levels were

monitored both manually and by pressure transducers. Manual recordings were

taken by a “dipper”, an electrical tape measure that emits an audible tone upon

contact with water (Figure 18).

Figure 18. Manual electrified tape measure

for the monitoring of water levels within

observation wells

Figure 19. Automatic groundwater level

logging equipment installed at monitoring well

090 and tipping bucket rainfall gauge

Additional data were obtained from two NRM & E monitoring wells equipped with

pressure transducers that are connected to continuous loggers (090 and 127).

Monitoring well 127 is located within the centre of the island towards the northern

end. Monitoring well 090 is located on the reference transect (NRM & E transect D-

D′) and is situated on the east coast of the island. Figure 19 illustrates the automatic

groundwater level logging equipment and the tipping bucket rainfall gauge located at

NRM & E well 090. Additionally, pressure transducers were used to monitor

groundwater levels during hydraulic testing.

46

However, monitoring well 090 is slotted in two different aquifers. It is possible that

water levels in 090 are the result of two different water bodies, thus analysis of water

level observations in this monitoring well is difficult.

The long-term hydrographs produced from the monitoring wells are used in the

analysis of secular and seasonal fluctuations. Expected fluctuations in groundwater

levels across the island will result from evapotranspiration, rainfall, barometric

pressure, and pumping.

5.1.4 Bailer tests

Pumping tests are expensive to conduct, both in terms of the cost of installation of

the pumping well and observation wells and also the time taken to perform the test

(Fetter 1994). As an alternative to a pumping test, bailer tests are a cost effective

estimate of the hydraulic properties of aquifers (Weight and Sonderegger 2000).

Bailer tests can be performed relatively quickly, so that several point estimates can

be collected.

A bailer test consists of measuring the recovery of head in a well after a near

instantaneous change in the water level. The bailer test begins with the sudden

removal of water via a bailer. Following the sudden change, the water level in the

well returns to static conditions as water moves into the well from the surrounding

aquifer. The rate at which the water level responds can be used to estimate the

hydraulic conductivity of the formation. An important factor that must be taken into

consideration during the analysis of bailer tests is the contribution of water from the

gravel pack surrounding the slotted section of casing/screen.

Bailer tests are highly suited to the small diameter monitoring wells located

throughout Bribie Island. The bailer consisted of a hollow cylinder of one litre

volume, constructed from stainless steel, that has a bottom valve to allow water to

enter but not exit during removal of the bailer from the well by the attached cable

(Figure 20).

47

Figure 20. Schematic illustration of bailer hydraulic test

A total of thirty bailer tests were conducted on shallow wells slotted within the upper

10 m of the island sediment. One litre of water was instantaneously removed from

the well resulting in a 0.5 m drawdown at time zero (t0). The rising head responses

were monitored manually, and analysed for hydraulic conductivity using the methods

of Hvorslev (1951) and Bouwer and Rice (1976).

5.1.5 Pumping tests

Although point estimates of aquifer properties can be obtained from bailer tests, the

results obtained via pumping tests can be of far more use (Weight and Sonderegger

2000). Pumping tests are conducted to obtain estimates of the general properties of

hydraulic conductivity and specific storage of an aquifer. Typically, a pumping test

will sample a much larger section of the aquifer than any other testing method,

therefore providing a more reliable estimate of the hydraulic properties of the

aquifer.

Tests usually require a pumping well and at least one observation well. Ideally, two

or more observation wells should be used to measure the effect of pumping at

48

different distances and at different heights within the aquifer. The water level in the

pumping well is lowered when pumping extraction begins, and this drawdown

creates a cone of depression around the pumping well. Observation wells within the

radius of the cone of depression will also show a lowered water level as illustrated in

Figure 21.

Figure 21. Schematic illustration of drawdown and cone of depression in a confined aquifer and the

relationship between the water level in the pumping well and in the observation well

The cone of depression expands outwards until enough water is captured to meet the

demands of the pumping rate (Weight and Sonderegger 2000). Additionally, the

shape of the cone of depression also depends on the nature of the aquifer material.

An aquifer of high hydraulic conductivity will produce a laterally extensive cone of

depression with a low hydraulic gradient. On the other hand, an aquifer of low

hydraulic conductivity will produce a cone of depression of steep hydraulic gradient

but not laterally extensive as illustrated in Figure 22.

The inverse relationship between hydraulic conductivity and the shape of the cone of

depression has a large impact on the design of a pumping test. Considering the

aquifer hydraulic properties are often unknown prior to the test, the dimensions of

the cone of depression are typically assumed via estimates. Thus, numerous

observation wells are needed to adequately monitor the effects of pumping on the

aquifer.

49

Figure 22. Schematic illustration of the differences in the shape of cones of depression in pumping

wells based on aquifer hydraulic properties (after Weight and Sonderegger 2000). The term K =

hydraulic conductivity

Additionally, the type of aquifer being tested also dictates the shape and size of the

cone of depression. Typically, a confined aquifer has a storage coefficient range

between 10-3 and 10-6, however, an unconfined aquifer has a specific yield range

between 0.03 and 0.3 (Weight and Sonderegger 2000). The significance of the

smaller storage value is that the cone of depression in a confined aquifer will extend

faster and further away compared to an unconfined aquifer. Semi-confined aquifers

are also common and have a large effect on the analysis of pumping tests. Layered

sediments may induce delayed yield or other sources of recharge.

In a situation such as Bribie Island where there is the possibility of confinement from

indurated sand layers, the pumping tests need to be designed accordingly. Particular

care must be taken to place observation wells within the expected radius of the cone

of depression and have numerous wells at various heights. These nested wells are

needed to monitor movement of groundwater levels within different sections of the

profile that may indicate confinement of the aquifer.

Four, 24 hour pumping tests were conducted in sets of partially penetrating nested-

monitoring wells. Table 7 presents information regarding pumping well

identification, duration of test, pumping rate and drawdown within the pumping well.

50

Table 7. Details of pumping tests

Test Date Pumping well Pumping time Pumping rate Maximum drawdown (min) (L/s) (m)

* 12/2/02 089 1380 0.30 0.607 1 20/3/02 101 1444 0.33 0.471 2 20/11/02 088 1443 0.33 4.316 3 5/8/03 089 1440 0.32 0.626

* = omitted from assessment due to unreliable test results

A Grundfos MP1 submersible groundwater-sampling pump with a discharge rate of

1.2 m3/hour was used for each test. Extracted water was discharged 300 m south

(down gradient) of the reference transect. Manual dippers and pressure transducers

monitored groundwater drawdown and recovery. During the pumping tests,

observation wells located across the reference transect were monitored at distances

up to 1.5 km away from the pumping well.

5.2 Hydraulic Tests Analysis

Data obtained from pumping tests and bailer tests includes water level drawdown

and recovery rates for both test wells and observation wells. Analytical solutions of

Theis, Theis Recovery, Cooper-Jacob and Stallman were used to estimate hydraulic

conductivity (K) and specific storativity (Ss) from pumping test data.

Bailer test data was analysed by the Hvorslev (1951) method and the Bouwer and

Rice (1976) method. The methods are quick to perform and are relatively simple in

procedure. As for all single well tests, these methods account for estimates of

hydraulic conductivity only - specific storage is not defined. Additionally, the

estimates of hydraulic conductivity are restricted to a particularly small section of the

aquifer immediately around the well slotted section/screen.

The Hvorslev method can be applied to confined and unconfined aquifer conditions

where the well is either fully or partially penetrating the entire thickness of the

aquifer. When the bailer of water is removed from the well the maximum

displacement value (h0) occurs instantly at time zero as illustrated in Figure 23. The

water level within the well is measured (ht) at time intervals (t) as the water level

returns to the original position. The ratio of ht/h0 is plotted on a graph verses time on

semi-logarithmic paper. The ratio between ht/h0 is plotted on the y-axis on a log

51

scale, and time along the x-axis. There are no type curves to match the data. The

time-recovery data should plot on a straight line. The graphical plot is required to

identify the parameter of T0 (time taken for the water level to rise 37% of the initial

maximum h0). The following formula applies:

( )0

2

2/ln

LTRLrK = (2)

Where;

K = Hydraulic conductivity (m/day)

r = Radius of the well casing (m)

R = Radius of well screen (m)

L = Length of the well screen (m)

T0 = Time for water level to rise 37 percent of h0

Bailer test data was also analysed by the Bouwer and Rice method. The Bouwer and

Rice method formula is as follows:

( )

=

t

o

e

ec

HH

tLRRrK ln1

2/ln2

(3)

The Bouwer and Rice method uses slightly different notation compared to the

Hvorslev method, but generally works on the same principle. The Bouwer and Rice

method is specific to unconfined aquifer conditions and also accounts for the well

geometry of partial penetration. Additionally, the Bouwer and Rice method accounts

for a fall in water level within the screened portion of the well. An adjusting value

needs to be calculated to account for the porosity of the packing material. This

adjustment is not needed if the water level is always located within the well casing

and does not fall below the top of the slotted section of casing. The Bouwer and

Rice method is commonly used in conjunction with the Hvorslev method as a means

of crosschecking values. In the following discussion of bailer test results the

estimates of hydraulic conductivity are reported from both method types.

52

Figure 23. Schematic illustration of the mechanics of a bailer test

A pumping test is one of the most useful means of determining hydraulic properties

of aquifers and confining layers (Kruseman and De Ridder 1979). Pumping tests

result in reliable estimates of aquifer hydraulic properties typically over much larger

areas than the point estimates of bailer tests. This is illustrated in Figure 23 & 24.

During each pumping test, water level time-drawdown data were plotted to identify if

steady-state conditions had been reached. Steady-state conditions exist when the

cone of depression ceases to expand and the water level within the pumping well and

observation wells ceases to fall with continued pumping. Steady-state conditions are

rarely achieved; however, it is necessary for the test to at least approach near steady-

state conditions (Kruseman and De Ridder 1979; Fetter 1994; Weight and

Sonderegger 2000). Additionally, if the aquifer is confined, the water must come

from a reduction of storage within the aquifer; therefore the head will decline as long

as the aquifer is effectively infinite (Kruseman and De Ridder 1979). Most

53

analytical solutions for pumping test analysis assume unsteady-state conditions;

however, most solutions are more reliable when steady-state conditions are

approached. Steady-state conditions are assumed when the rate of head decline is

negligible. When steady state conditions are approached, the pump may be stopped

and the second part of the pump test begins. The water level recovery within the

pumped well and the observation wells is also very useful in the analysis of the

hydraulic properties of the formation.

Figure 24. The mathematical region of flow for a pumping test, is a horizontal one-dimensional line

through the aquifer, from r = 0 at the well to an infinite extremity

54

After each pumping test was completed the water level time-drawdown and time-

recovery data was compiled from all observation wells and the pumped well. The

data was initially processed via graphical analysis to identify drawdown within any

observation wells. Observation wells that showed no sign of drawdown were

omitted from further analysis.

Drawdown and recovery curves for the pumped well and the observation wells were

also checked for signs of additional influence such as delayed yield and barometric

influence. Barometric influence typically affects the water level within wells that are

confined to semi-confined. Barometric efficiency is indicative of the degree of

confinement; the more confined an aquifer the larger the barometric influence on the

piezometric head. Pressure changes within the atmosphere cause the water level to

fluctuate within well. For example, as atmospheric pressure increases, the water

level within the well will fall slightly and vice versa. Therefore, atmospheric

pressure must be monitored during the test. The influence of the barometric pressure

must be removed from the water level time-drawdown data to find the correct levels

during the pumping test. Well barometric efficiencies typically range from 20 to 70

% (Todd 1979). Barometric efficiency is calculated as follows:

*factor conversion x (hPa)n fluctuatio Pressure(cm)n fluctuatio eWater tabl

=α

* Conversion factor = 0.9835 cm H2O / hPa @25 oC

(4)

Semi-confined (leaky) aquifers are a common feature of many unconsolidated

formations such as deltas, coastal plains, and lowland river valleys (Kruseman and

De Ridder 1979). A delay in yield is often a result of semi-confined conditions

where leakage from overlying or underlying confining layers contributes water to the

tested aquifer. The rate of leakage is determined from the head difference between

the aquifer and the confining layer and also the hydraulic conductivity of the

confining layer. The hydraulic conductivity of the confining layer is typically

several orders of magnitude lower than that of the aquifer (Weight and Sonderegger

2000). Time-drawdown graphical plots were analysed for evidence of delayed yield.

Typically, the contribution of water to the aquifer from the confining layer results in

a flattening of the time-drawdown curve. Evidence of delayed yield suggests that

appropriate analytical solutions be used in the analysis of the pumping test data. If

55

delayed yield does not exist, the traditional analytical solutions for an unsteady-state

confined aquifer can be used.

Both the Theis (1935) method and the Theis recovery method account for confined

aquifers in unsteady-states. The following limiting conditions should be satisfied

when using either of these analytical solutions (Kruseman and De Ridder 1979):

1. the aquifer has seemingly infinite areal extent

2. the aquifer is homogenous, isotropic and of uniform thickness

3. nearly horizontal piezometric surface prior to pumping

4. constant discharge rate

5. the well penetrates the entire thickness of the aquifer

6. the aquifer is confined

7. the flow to the well is unsteady-state

8. water removed from storage is discharged instantaneously with

decline in head

9. the diameter of the pumped well is small (limited well storage)

The Theis method is a graphical means of solution based on type curves for the

estimation of aquifer hydraulic conductivity (K) and storativity (S). The Theis

equation is expressed (Driscoll 2003):

)(41 uWT

Qs π= (5)

W(u), the well function of u, is an abbreviation for the exponential integral:

•••+•

+•

+•

−+−−==∫∞ −

!44!33!22log5772.0)(

432 uuuuuuWdxx

ee

u

x

(6)

Where;

Q = Pumping rate (L3/t)

T = Transmissivity (L2/t) – hydraulic conductivity (K) x aquifer thickness (b)

s = Drawdown (L)

W(u) = Well function of u (dimensionless)

56

The well function of u is expressed:

TtSru

4

2

= (7)

Where;

r = Radial distance to the pumping well (L)

S = Storage coefficient (dimensionless)

T = Transmissivity (L2/t) [hydraulic conductivity (K) x aquifer thickness

(b)]

t = Time (days)

In the equation, the infinite series in brackets is known as the well function (W(u)).

Reverse type curves are created by plotting values of the well function (W(u)) against

1/u on a logarithmic scale. Field data for drawdown (s = h0 – h) is then plotted

against t/r2 on another sheet with the same logarithmic scale as the type curve. The

curve of the plotted field data should be similar to the type curve as illustrated in

Figure 25.

Figure 25. Analysis of data from pumping test with the Theis method (after Kruseman and De Ridder

1979)

The two curves are placed over each other and aligned so that the field data best

matches a portion of the type curve. An arbitrary point is selected on the plots.

Typically the point selected has the coordinates of W(u) = 1, and 1/u = 10. From this

57

point the values for s and t/r2 are determined. The values of Q, W(u), 1/u, s, and t/r2

are then substituted into the rewritten equations of:

Transmissivity )(4 uWs

QTπ

= (8)

Storativity 2

4rTtuS = (9)

After the pumping test has ceased, the water level within the pumping well and

observation wells begins to rise back to the original position. This portion of the test

is referred to as the recovery of the well. The data obtained during the recovery

period of the pumping test can only be used to calculate hydraulic conductivity. The

results from recovery tests provide a check on the results of the pumping test data.

The rise of the water in the well is termed the residual drawdown (s'). The residual

drawdown is measured as the difference between the original water level prior to

pumping and the actual water level measured at a certain moment (t') since pumping

stopped. The residual drawdown is expressed by Theis (Kruseman and De Ridder

1979) as:

−=

''4ln

r4ln4' 22 Sr

KbtS

KbtKb

Qs π (10)

Where;

s' = Residual drawdown (L)

R = Distance from pumped well to observation well (L)

S' = Storage coefficient during recovery (dimensionless)

S = Storage coefficient during pumping (dimensionless)

t = Time since pumping started

t' = Time since pumping stopped

Q = Rate of discharge = rate of average recharge (L3/t)

For each observation well the residual drawdown is plotted on a semi-logarithmic

scale against the ratio of t/t'. A straight line should be able to fit through most of the

data, although early time data often does not fit well. The straight line through the

plotted points has a residual drawdown difference per log cycle of t/t'. Therefore,

when the S and S' are constant and u = r2S/4Kbt' is sufficiently small the equation

can be rearranged to:

58

'430.2

sQKb

∆= π

(11)

Where;


b = Aquifer thickness (L)

Q = Rate of discharge = rate of average recharge (L3/t)

∆s' = Residual drawdown difference per log cycle of t/t'

5.3 Water and Sediment Sampling

Samples of water and sediment are used extensively within this study to facilitate

greater hydrogeological understanding; however the collection and storage of these

samples require care.

Water sampling is best associated with the monitoring of trends in water properties

over time. This time-series analysis often highlights important aspects of the

groundwater regime. Sediment samples are typically taken during the drilling

process. The collection and analysis of sediment samples enable the development of

geological logs and detailed stratigraphic cross-sections through the profile of the

formation.

5.3.1 Sediment samples

Sediment samples were collected at 0.5 m intervals during the drilling of each

groundwater well. Formation samples were returned to the surface through the

annulus around the drill rod and the drill hole in slurry of drilling fluid. The samples

were directed into a settling tank from which the samples were collected. The

samples were collected in marked bags and laid out in sequential order for detailed

geological logging (Appendix D). Additionally, SPT samples were collected at

intervals of interest, particularly through the indurated sand layers and at the

lithology change of the sandstone bedrock. The geological logs were compiled to

create a detailed geological cross-section through the profile of the island.

59

5.3.2 Age dating sampling

During the drilling of the monitoring well network, four samples were specially

extracted for optically stimulated luminescence (OSL) age dating analysis. The four

samples were removed from drill hole number 140 (Figure 16) at sections of the

profile that showed clean marine derived quartz sands. The samples were extracted

at depths of 1.5m, 4m, 10m, and 20m (Table 8). Samples were collected in the same

manner as standard penetration tests (SPT) samples are obtained. Upon reaching the

surface the SPT tube was slipped into an opaque sleeve to prevent sunlight entering

the ends or the split of the sampling tube. Once the sampling tube was disconnected

from the drill rod the tube was transferred into an opaque handling bag where the

tube was opened and the contents transferred into air tight, opaque containers.

Table 8. Sediment sampled details for OSL analysis

Sample

No.

Depth

(m)

Sediment description

BI-1 1.5 – 1.9 Foredune and beach sands - med-fine grained sand

BI-2 4 – 4.2 Indurated sand - dark brown/black, fine-med grained highly indurated

sand

BI-3 10 – 10.2 Weakly indurated sand - dark brown, med grained with some fine gravel

BI-4 20 – 20.2 Brown sand - med-fine grained with some thin lenses of weakly indurated

sand

5.3.3 Age dating analysis

This method of sediment dating makes use of the condition that daylight releases

charge from light-sensitive electron traps in crystal lattice defects in minerals such as

quartz and feldspar. This release of trapped charge by light resets the optically

stimulated luminescence (OSL) signal; the process is commonly referred to as

bleaching. When grains of quartz are buried and no longer exposed to light, they

begin to accumulate a trapped-charge population due to the effects of ionising

radiation, such as that arising from radionuclides naturally present in the deposit.

This trapped-charge population increases with burial time in a measurable and

predictable way. The OSL samples were sent to the CSIRO Land and Water

laboratories in Canberra. The OSL method is detailed in appendix E.

60

5.3.4 Water Sampling

Water samples were collected across the central section of Bribie Island for both

groundwater and surface water. The sampling period for both groundwater and

surface water was conducted from September 2000 to July 2002; the interval

between sample collections ranged between six months to one year. Groundwater

and surface water samples were collected from all available wells and surface water

bodies throughout the central section of Bribie Island as illustrated in Figure 16 and

Figure 26.

AS/NZS 5667.11-1998 Water Quality - Sampling Part 11: Guidance on sampling of

groundwaters, the 1992 ANZECC publication Australian Water Quality Guidelines

for Fresh and Marine Waters and the MDBC Groundwater Working Group 1997,

Murray-Darling Basin Groundwater Quality Sampling Guidelines, Technical Report

No. 3, Murray Darling Basin Commission Groundwater Working Group, were used

as the primary reference documents in the sampling/analysis of groundwater and

interpretation of results.

Ninety-nine groundwater water samples were extracted. Typically, all monitoring

wells were sampled three times during the sampling period. Groundwater samples

were extracted from monitoring wells via small down-hole sampling pumps.

Discharge was directed from the wellhead into the bottom of a small (10 L) container

to minimise aeration of the sample. Purging of the monitoring well for at least three

times the volume of the casing prior to collection of the sample ensured a

representative sample from the formation. Collection and storage of a sample was

within 500 mL polyethylene sample bottles. Sample bottles were prepared with a

wash of 1:3 diluted HNO3 to avoid contamination, and separate bottles used to store

samples for cation and anion analysis. Sample bottles for cation analysis were

acidified with 1 mL HNO3 to slow chemical reactions and stable metals. Both cation

and anion samples were cooled immediately and stored at 5 oC.

Surface water samples were collected with a similar technique for the collection of

groundwater samples. Minimal aeration of water samples was best achieved by

gentle insertion of the bottle beneath the water body surface. Forty-five surface

61

Figure 26. Locations of surface water sampling points. Samples were collected between September

2000 to July 2002 and in most cases represent wetlands

62

water samples were collected. Similar to groundwater samples, separate 500 mL

sample bottles were used for cation and anion storage. Surface water samples were

also stored in cool conditions.

Both groundwater and surface water samples were filtered at the School of Natural

Resource Sciences (NRS) chemical laboratory. For most samples, the level of

turbidity was not considered high enough to warrant field filtering of samples.

Determination of alkalinity and elemental testing of cation and anion concentrations

was also carried out within the laboratory. Groundwater and surface water samples

were also analysed for non-volatile organic compounds. These natural non-volatile

constituents include organic compounds such as fluvic, humic and tannin acids.

Typically, samples with a pale yellow to brown appearance suggest a high

concentration of organic compounds.

The physico-chemical parameters pH, electrical conductivity (EC), temperature (oC),

redox potential (Eh), and dissolved oxygen (DO) were also determined in the field

for both groundwater and surface water samples. These parameters were measured

using a TPS 90 FL microprocessor multi-probe field analyser, and conducted at the

time of sample collection.

The TPS 90 FL analyser was calibrated within the NRS laboratory prior to field use.

EC measurements were calibrated against standards of comparable ionic strength.

The pH probe was calibrated against buffered standards of pH 4 and pH 7. A

standard Zobell solution was used for the calibration of the Eh probe. Field

measurements of Eh were converted to standard hydrogen electrode units by adding

+267 mV.

5.3.5 Elemental analysis

Elemental analysis of water samples was carried out in the NRS chemical laboratory.

The cations Na, K, Ca, Mg, Fe, Al, Si, Mn, Zn were analysed via the Varian Liberty

200 Inductively Coupled Plasma – Optical Emission Spectrometer (ICP-OES), and

calibrated against four synthetic cation standards. Anions Cl, HCO3, SO4, F, Br, N,

63

PO4 were analysed via the DX300 Dionex Ion Chromatograph. Alkalinity was

determined by acid titration.

Organic carbon was analysed using the Shimadzu Total Organic Analyser (TOC-

5000A) in the School of Civil Engineering laboratory. The determination of total

carbon and inorganic carbon was based on the combustion/non-dispersive infrared

gas analysis method. When the total carbon and the inorganic component were

determined, the organic carbon was calculated as “total carbon minus inorganic

carbon”. In addition, the cation-anion balance was adjusted for the contribution of

dissolved organic matter. From a measurement of the pH and TOC of a water

sample, the mass action quotient of the fluvic and humic acids (organic anion A-) can

be estimated using an empirical equation.

The sum of the positive and negative charges of all elements within the sample

should approximate a balance. The accuracy of the analysis can therefore be

checked by estimating the electro neutrality of the water sample expressed by:

100 % neutrality Electro ×

−

+=∑ ∑∑ ∑

anionscationsanionscations

(12)

An error percentage of ± 10 % was considered tolerable.

64

6.0 RESULTS

This study of hydrogeology of the sand aquifers of Bribie Island integrates a number

of separate aspects. Findings and results obtained during the course of this

investigation from field, laboratory, and computer-based analysis can be summarised

as follows:

a) Island stratigraphy

Stratigraphic features of Bribie Island are identified using monitoring well

log data. The well logs identify a stratigraphy of various units of

unconsolidated and indurated layers throughout the island profile.

b) Island evolution and age

Age dating analyses of sediment samples collected during the drilling

program provide estimates of island evolution and age. The sediment age

dates indicate stages of island formation relative to sea level fluctuation

associated with major periods of glaciation throughout the Quaternary.

c) Island hydrology

Data obtained from monitoring wells across an island transect illustrate a

stratified aquifer system consisting of an elevated water table and basal

groundwater. Groundwater flow directions are also analysed through

contouring of groundwater heads across the island profile.

d) Water geochemistry

Groundwater flow through Bribie Island is also expressed by groundwater

and surface water geochemistry. Aquifer lithology can be distinguished

via elemental chemistry that reflect different water bodies, plus mixing.

Additionally, groundwater–surface water relationships can also be

indicated.

e) Aquifer hydraulic tests

Data obtained from hydraulic tests can confirm the heterogeneous

structure of an aquifer system such as Bribie Island. Sections of the

65

island profile are assigned the hydraulic properties of hydraulic

conductivity and specific storage. Confining layers are identified and

their influence on the groundwater regime is assessed.

6.1 Island Stratigraphy

Typically, the exposed uppermost sediments often mask the subsurface geology of a

barrier island. As a consequence, drill logs provide an understanding of the

subsurface geology of these islands. The drill logs of Bribie Island identify a

stratigraphy of various units of unconsolidated and indurated layers throughout the

island profile. Figure 27 illustrates the depth of drilling of each drill hole across the

reference transect (NRM & E D-D′) and also indicates where monitoring well slotted

sections are located. Detailed geological logs are located within appendix D. The

cross-section of Figure 27 also indicates topographical features.

6.1.1 Aquifer Description and Distribution

Palaeochannel Aquifer

At the bottom of the unconsolidated sediment profile (within the palaeochannel) is an

8-10 m thick unit consisting predominately of medium grained sand. The

palaeochannel aquifer overlies the weathered sandstone bedrock and also includes

some thin lenses of fine sand, coarse sand and a gravely base. This unit may

represent tidal channel (inlet) or tidal-delta facies, however, both sequences are

difficult to determine from geological logs due to the lack of observable bedding

structures (e.g. Reinson 1984). Typically, both of these sequences are associated

with barrier-inlet modes (stationary barriers) of barrier island formation (Figure 2).

Transgressive, regressive (progradational), and barrier inlet depositional conditions

can occur in combination to produce mixed sequences which have affinities with

more than one “end-member” mode of barrier island formation. Therefore,

considering the formation and evolution of Bribie Island, it is suggested that a

combination of modes may have existed. The existence of barrier inlet facies at

depth is in contrast with the typical coarsening up profile associated with strandplain

and progradational barrier island deposits (Figure 3). However, various episodes of

66

marine transgression and regression have the potential to truncate older sequences

and add overlapping deposits (McCubbin 1984). The mode of deposition during

these transgressions and regressions may vary and result in sequences of mixed

modes. The deep tidal inlet unit at the base of the Bribie Island sand mass is

considered to be remnant from an older truncated barrier island sequence, on which a

progradational barrier island/strandplain sequence was deposited.

Typically, the vertical sequence model for progradational barrier deposits coarsens

upward (Figure 28) from offshore deposits consisting of dominantly sandy silt with

some thin beds of sand, to the lower shoreface where the sand fraction increases

(Galloway and Hobday 1983). The lower shoreface coarsens upward into the upper

shoreface where the fine to medium grained sand has been deposited in the sub-tidal

region by wave surge and wave generated currents (McCubbin 1984). Foreshore and

beach sequences of fine to medium grained sand are deposited by wave swash in the

intertidal zone. The Bribie Island vertical sequence resembles this model.

Offshore Sandy Silt Aquifer

A sequence of offshore deposits consisting of sandy silts overly the palaeochannel

aquifer. The sandy silts are light olive-grey in colour and contain thin lenses of fine

sands and clay. The maximum thickness of this sequence is towards the centre of the

island at 15-20 m. The top of the sequence of clayey sands is approximated by the

depth of increased response in the gamma logs shown in Figure 27.

Shoreface Brown Sand Aquifer

Shoreface deposits of prograding sand dunes constitute the most widespread unit

within the island and consist of fine-medium grained quartz sand. The colour of the

sand is light brown. Across the reference transect, the brown sand aquifer is thickest

towards the middle of the island at 12 m.

Fi

gure

27.

Geo

logi

cal c

ross

-sec

tion

of B

ribie

Isla

nd a

cros

s the

refe

renc

e tra

nsec

t D-D′.

Var

ious

iden

tifie

d se

dim

ent u

nits

are

indi

cate

d by

shad

ing.

Mon

itorin

g w

ell c

asin

g

and

slot

ted

sect

ions

are

als

o in

dica

ted.

Wel

ls d

rille

d by

Que

ensl

and

Dep

artm

ent o

f Nat

ural

Res

ourc

es a

nd M

ines

: 088

, 089

, 090

, 100

, 101

, 126

and

129

; Wel

ls d

rille

d by

Que

ensl

and

Uni

vers

ity o

f Tec

hnol

ogy:

136

, 137

, 138

, 139

, 140

, 141

, 142

, 143

, 144

, 145

, 146

, 147

, 148

, 149

, 150

and

151

. A

lso

show

n ar

e do

wn

hole

gam

ma

logs

(NR

M &

E un

publ

ishe

d da

ta)

67

hoshiko

Rectangle

halla


68

Figure 28. Generalised vertical sequence of progradational barrier sequence from offshore to beach

deposits (after McCubbin 1982)

Indurated Sand Layer

Contained within the shoreface sediments is a dark brown to black indurated sand

layer at an approximate depth of 5-6 m. The layer has a maximum thickness of 9 m

(Figure 27). The quartz sand grains have been cemented together by the infilling of

pores by a variety of cements, predominately organic matter and clays (Farmer et al.

1983; Thompson et al. 1996; Cox et al. 2002). Shell and vegetative matter were not

69

detected in the indurated sand layer. Thin layers of coarse-grained indurated sand

were often encountered.

Foreshore and Beach Sand Aquifer

Typically, the uppermost foreshore and beach medium-fine grained sand aquifer is

white to grey in colour and has a thickness of approximately 5 m. The medium-fine

grained sand often contains a limited amount of root and organic material to a depth

of approximately 0.5 m. Shell material is considered by the Queensland Department

of Primary Industries – Forestry to represent aboriginal midden heaps and are

generally restricted to the surface and near surface sands (personal communication,

Stan Ward, DPI-Forestry). The standing water table was typically intersected within

a range from 0.5 m-1.5 m.

6.2 Island Evolution and Age

Age dating sediment samples were taken at various heights through the profile of the

island during the drilling of monitoring well 140. The samples were from the

following parts of the island sand profile; sample 1 from within the uppermost dune

sands at a height of 1.5 m; sample 2 from within the indurated sand layer at a depth

of 4 m; sample 3 from just beneath the indurated sand layer within weakly indurated

sand at a depth of 10 m; and sample 4 from within the brown sand unit at a depth of

20 m. Table 9 lists the age determined for each sample.

Table 9. Calculated burial ages of sediment samples from Bribie Island drill hole (monitoring well

140)

Sample Depth (m) Age (ky) BI-1 1.5 m 63.5 ± 8.5

BI-2 4 m 90 ± 18

BI-3 10 m 180 ± 40

BI-4 20 m 310 ± 70

The OSL derived ages from the sand samples of Bribie Island plot against a glacio-

eustatic sea level curve for the last 340 000 years as illustrated in Figure 29. The

curve can be used to give an indication of sea level cycles that may have affected

Moreton Bay. The deposition of the sediment samples appears to have occurred

70

within three phases. Each sample was deposited during a period of regression

associated with major glaciation events. The regression of mean ocean levels

enabled the progradation of beach ridge systems and the formation of the Bribie

Island strandplain/barrier island.

Due to the prograding nature of some barrier sand islands, the formation and

evolution of the island can often be interpreted by the characteristic dune ridge

structures. These dune ridge systems typically reflect the number of phases of

development. The evolution of these dune systems is often illustrated with a series

of time line approximations (Figure 3a).

The sediment age dates for Bribie Island suggest the island may have developed

within three phases as illustrated in Figure 29. Older beach ridge series are situated

landward (to the west of well 140) and are progressively less preserved and less

defined westward. The western beach ridges are believed to have formed during

separate pre-glacial progradations. Coastal dunes have formed along the fringe of

the island as a result of a slight sea level fall within the last 6000 years (Jones 1992).

6.3 Island Hydrology

The groundwater resources across the reference transect can be divided into a

shallow unconfined water table aquifer and basal semi-confined aquifers. These

upper and lower aquifers are characterised by different hydrological processes,

physico-chemical properties, and water chemistry.

72

6.3.1 Groundwater levels

Monitoring of groundwater levels throughout Bribie Island was undertaken to

identify trends in groundwater recharge, migration and discharge. Typically,

examination of shallow monitoring well hydrographs indicate a tendency for the

water table to respond rapidly to rainfall events while the deeper wells beneath the

indurated sand layer experience a slight delay in recharge; this trend was also

reported by Harbison (1998). Detailed analysis and interpretation of groundwater

levels across Bribie Island has identified that groundwater movement is partly

controlled by the geological framework of the island. To better test this finding the

reference transect was constructed with twenty-three monitoring wells such that

shallow, intermediate and basal groundwater bodies are adequately monitored.

Long-term hydrographs of nests of monitoring wells across the reference transect are

illustrated in Figure 30. Appendix F contains groundwater level data. Each

hydrograph illustrates a nest of wells from the eastern beach ridge (A) to the western

beach ridge (H) for the period of April 2001 and June 2002.

Unconfined conditions prevail in the upper dune sands. The hydrographs indicate

monitoring wells slotted within the upper dune sands above the indurated sand layer

have consistently elevated water level trends (Figure 30). The water table contour

generally follows local topography forming distinct mounds beneath the two beach

ridge systems. The water table is often proximal to the surface and has an

approximate maximum elevation towards the centre of the island at 7 m above mean

sea level (Figure 30).

Groundwater levels illustrated on Figure 30 (Appendix F) show significant decline in

water levels in wells located near the central swale (i.e. wells 129, 144, 146 &147)

during the period of measurement. This decline in head near the central swale may

be the result of reduced groundwater flow from the more elevated dune systems. The

reduced groundwater flow may result in a decline in the hydraulic head within the

dune system during drought conditions

73

Monitoring wells slotted beneath the indurated sand layer show lower water level

trends than the elevated water table (Figure 30). Due to the confining nature of the

indurated layer the basal groundwater occurs under semi-artesian conditions and has

a piezometric surface that is relatively flat across the island. The piezometric surface

typically ranges between 2-3 m above mean sea level with a slight mound beneath

the eastern beach ridge.

The continuous groundwater level monitoring of two NRM & E wells (127 and 090)

by automated data loggers also show the hydraulic gradient of the contrasting heights

between the water table and the piezometric surface as illustrated in Figure 31.

Monitoring wells 127 and 090 both display significant response to rainfall events

(Figure 31), however, the response is greater for the shallow monitoring well 127.

Both wells also show significant correlation with rainfall events. Delayed recharge is

negligible within the deeper monitoring well 090, however, it is possible that well

construction may impact on these results.

The construction of well 090 includes two slotted sections both of which are located

beneath the indurated sand layer (Figure 27). Additionally, the annulus between the

drill hole and the well casing has not been installed with seals between the two

slotted sections nor is there a seal within the indurated sand layer. These seals would

prevent drainage from other sections of the aquifer and from above the indurated

sand layer. The connectivity between aquifers may result in anomalous results that

suggest a negligible delayed yield and an exaggerated response to rainfall for the

deeper well.

74

Figure 30. Hydrographs of water levels from nested monitoring wells across the reference transect

(Figure 27) plotted against rainfall for the period April 2001 to May 2002: A (eastern beach ridge) to

H (western beach ridge). Monitoring wells slotted within the upper dune sands above the indurated

sand layer consistently show elevated water level trends. Appendix F contains groundwater level data

75

Figure 31. Hydrographs from automatic loggers on monitoring wells 127 and 090 illustrate a rapid

response to rainfall

The stratification of head gradients across the reference transect contrasts with the

“classical” domed water table conceptual model expected of a barrier island. The

hydraulic gradient that exists between the water table and the piezometric surface is

illustrated in Figure 32. The vertical head gradient is steepest through the centre of

the island where topography is also greatest. Equipotential lines and flow direction

identify the shallow hydraulic gradient within the central swale.

In three dimensions, the discharge from the foreshore and beach sand unit is likely to

be southwards towards Wright’s Creek. The low vertical gradient in the upper

shoreface deposits rather implies lower vertical flow within the central swale.

Contouring head values across the reference transect enables an appreciation of

aquifer heterogeneity. The flow net illustrated in Figure 33 accounts for the different

hydraulic properties across Bribie Island as determined from the geological and

76

hydraulic analysis. The flow net shows high hydraulic gradients through the low

permeability units, and low hydraulic gradients within high permeability units.

Figure 32. Water level contours across the reference transect for 10 April, 2001 which clearly

demonstrate the elevated water table and the piezometric surface of the basal aquifers

Groundwater flow within the upper dunes has a distinct lateral flow as well as

vertical flow. Seepage of shallow groundwater has been observed as “return flow”

across the top of indurated sand exposures along the coastline. Groundwater

migrates downward through the indurated sand layer to the basal water body where

groundwater flow is directed towards both coastlines (Figure 33). The equipotential

lines illustrated in Figure 33 are shown as sub-horizontal within the upper shoreface

deposits indicating the predominant direction of groundwater flow is likely to be

vertical in the low permeability unit (indurated sand). Measured heads from wells

77

142 and 143 indicate a large vertical hydraulic gradient at the top of the upper

shoreface deposits, suggesting that the indurated sand zone might be least permeable

at the upper surface of the unit.

6.4 Barometric Efficiencies

Water levels observed in wells are commonly affected by barometric pressure (Davis

and Rasmussen 1993). The rate of the change in the water level in a well to the

change in atmospheric pressure that produces it is known as the barometric

efficiency (Clark 1967). An inverse relationship exists where an increase in

barometric pressure produces an apparent decline in water within the well. These

water level fluctuations often create difficulties during the analysis of regional water

levels and pumping test data. Water level fluctuations must therefore be eliminated

to highlight the true trend of the water level over time. Obtaining an estimate of

barometric efficiency from a record of water levels and barometric pressures is not

straight forward when there are large variations in water level due to causes other

than changes in barometric pressure, such as temporal variations in regional recharge

and discharge rates and earth tides (Davis and Rasmussen 1993).

A method developed by Clark (1967) involves determining the incremental changes

in the water level, ∆W, and in the barometric pressure, ∆B. Clark’s method assumes

that the barometric efficiency is a constant and that rapid equilibration occurs

between a change in barometric pressure and water level response in wells (Davis

and Rasmussen 1993). The Clark method eliminates incremental changes in the

water level that are not attributed to barometric influence by the use of the following

four rules:

Fi

gure

33.

Flo

w n

et a

cros

s the

refe

renc

e tra

nsec

t usi

ng a

vera

ged

grou

ndw

ater

leve

ls.

The

stee

p hy

drau

lic g

radi

ent t

hrou

gh th

e in

dura

ted

sand

laye

r (ill

ustra

ted

by

equi

pote

ntia

l lin

es) i

ndic

ates

the

laye

r may

hav

e a

redu

ced

hydr

aulic

con

duct

ivity

. B

ased

on

wat

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dat

a re

cord

ed o

n 10

th A

pril

2001

78

79

1. when ∆B is zero, neglect the corresponding value of ∆W in obtaining

Σ∆W,

2. when ∆W and ∆B have like signs, add ∆W in obtaining Σ∆W,

3. when ∆W and ∆B have unlike signs, subtract ∆W in obtaining Σ∆W,

and

4. the value of ∆W is given a positive sign when the water level is rising,

and ∆B is given a positive signs when the atmospheric pressure is

decreasing.

The barometric efficiency of the well is then estimated by:

BW Σ∆Σ∆= /α (13)

Where;

α = Barometric efficiency (%)

∆W = Change in water level elevation (L)

∆B = Change in barometric pressure head (L)

The Clark method was used on water level records from monitoring wells 088, 089,

100 and 101. Water level and barometric records were taken over a one-month

period at time intervals of 0.5 hr (wells 088 and 101) and 2 hr (wells 089 and 100).

Cumulative absolute changes in water level (Σ∆W) were plotted against

corresponding values of Σ∆B (Figure 34). The slope of a linear trend through the

data was taken to equal barometric efficiency. Barometric efficiencies for each well

are presented in Table 10; also included are the standard error for each regression

slope. Percentage error for each barometric efficiency approximates 0.1 %.

Table 10. Barometric efficiencies (expected value ± one standard error)

Clark’s method Harbison

(1998) Well Stratigraphic Unit

% S.E. % %

088 Offshore deposits - sandy silts aquifer 7 ± 0.72 12

089 Channel deposits – palaeochannel aquifer 3 ± 0.14 11

100 11 ± 0.15 40

101 Upper/lower shoreface deposits - brown sand aquifer

58 ± 0.09 88

Standard error reported as percentage of estimate

80

Also included within Table 10 are results presented by Harbison (1998). The curve

matching approach used by Harbison (1998) adjusts water levels to a constant

atmospheric pressure using assumed values for barometric efficiency. The curve

matching method requires the use of personal judgement and hence, barometric

efficiency may be overestimated. For this reason it is suggested that the values of

barometric efficiency for wells 088, 089, 100 and 101 derived by the Clark method

are a more robust estimate.

Following the method of Rasmussen and Crawford (1997), step response functions

for wells (088, 089, 100 and 101) were generated by ordinary least squares (OLS)

analysis of barometric pressure and water levels. Standard error terms were

calculated from sum of square errors. Data was initially de-trended by subtraction of

26-hour running means. Residual water levels in two wells (100 and 101)

demonstrated step responses typical of aquifer confinement (Figure 35). For

borehole 100, a slight delay in response indicates a "skin effect" in the response

function. For two deeper wells (088 and 089), the barometric efficiency is

considerably less, and the component of water levels affected by barometric pressure

are difficult to de-trend. As a result, standard errors for these wells are greater than

the step response values. Nevertheless, slow rising step response indicates that a skin

effect is possible for wells 088 and 089 (Figure. 35).

Figure 34. Computation of barometric efficiency for monitoring wells A) 088 = 7 %, B) 089 = 3 %, C) 100 = 11 % and D) 101 = 58 % 81

82

Figure. 35 Barometric response functions for wells 088, 089, 100 and 101

6.5 Water Geochemistry

Groundwater flow through Bribie Island is also reflected through groundwater and

surface water chemistry. Aquifer lithology can be distinguished via elemental

chemistry and physico-chemical characteristics; in addition, groundwater-surface

water relationships are also evident.

6.5.1 Physico-chemical properties

Field measurements of dissolved oxygen (DO), electrical conductivity (EC), redox

potential (Eh), pH and temperature were determined for 45 surface water samples

and 99 groundwater samples (Appendix G). Physico-chemical averages of

groundwater and surface water samples collected through the sampling period of

September 2000 to July 2002 further characterise the different water bodies on Bribie

Island as illustrated in Table 11.

83

Table 11. Average physico-chemical parameters for groundwater and surface water of Bribie Island

Sample DO (ppm) EC (µS/cm) Eh (mV) pH Temp. (oC)

Semi-confined groundwater 0.7

(0.1-1.0)

355

(50-1100)

216

(137-333)

6.2

(4.4-7.1)

22

(18-24)

Unconfined groundwater 2.8

(05-6.0)

279

(56-568)

279

(185-387)

3.9

(3.0-4.7)

20

(17-24)

Wetlands and Excavations 4.8

(1.9-7.2)

220

(87-516)

413

(249-576)

3.5

(2.2-4.4)

23

(17-29)

Coastal lagoons 7.8

(7.3-8.7)

44 750

(44 400-45 100)

389

(383-395)

7.5

(7.0-8.1)

28

(25-30)

September 9th 2000 to July 30th 2002 Range of values shown in brackets

Electrical Conductivity

The majority of groundwater and surface waters on Bribie Island are fresh, with the

exception of coastal lagoons, tidal creeks, and saline influenced groundwater.

Groundwater within the unconfined dune sands typically has low EC values with a

range of 56-568 µS/cm, with an average of 279 µS/cm (Table 11). Typically, the

values for EC from wetlands and surface excavations range from 87-516 µS/cm,

similar to the values for the shallow unconfined groundwater. Surface water

contained within coastal lagoons has EC values up to 45 100 µS/cm indicating

seawater as a large constituent of lagoon volume. Groundwater within the sediments

beneath the indurated sand layer has a range of EC values from 50-1100 µS/cm, with

an average of 335 µS/cm.

pH

Groundwater influenced by differing processes may be distinguished by differences

in pH trends (Driscoll 2003). The pH of groundwater contained within sediments

beneath the indurated sand layer is approximately two units more alkaline than either

unconfined groundwater or surface water as illustrated in Table 11. The basal

groundwater has the highest pH values of groundwater within the island ranging

from 4.4-7.1, with an average of 6.2. Groundwater contained within the unconfined

foredune and beach sands has pH values ranging from 3-4.7, with an average of 3.9.

Values of pH from wetlands and surface excavations range from 2.2-4.4, with an

average of 3.5. The acidic pH values of the unconfined groundwater and surface

84

water result from the decomposition of organic matter originally derived from

vegetation. Fallen leaf litter decomposes to produce organic acids and dissolved

organic carbon.

Colour

Rainfall events flush organic acids and dissolved organic carbon into the island

wetlands, where they percolate down to the unconfined water table (Harbison 1998).

A dark colouring of the unconfined groundwater and surface water is attributed to

high concentrations of dissolved organic carbon. The dark brown to black colouring

of this low pH water is often referred to as “black water”, and is common of many

low-lying poorly drained coastal settings (Laycock 1975; Revee et al. 1985; Pye

1982). The unconfined dark coloured groundwater has a range of colour of 441-

2080 Hazen units; surface waters are typically very dark coloured and have a range

of 910-6560 Hazen units. The deeper semi-confined groundwater in comparison is

clear to colourless water with a range of 11-467 Hazen units.

Redox potential and dissolved oxygen

All groundwater and surface water samples from throughout Bribie Island indicate

oxidising conditions. Unconfined groundwater typically has a range of Eh values of

+185 to +387 mV, with an average of +279 mV (Table 11). Typically, the values of

Eh from wetlands and surface excavations range from +249 to +576 mV.

Groundwater sourced from beneath the indurated sand layer has a range of Eh values

from +137 to +333 mV, with an average of +216 mV. Dissolved oxygen

concentration is greatest within the coastal lagoons with an average of 7.8 mg/L,

while other surface waters such as wetlands and excavations have average DO values

of 3.2 and 7.2 mg/L, respectively.

6.5.2 Major ion chemistry

Major and minor ion concentrations have been determined for 99 groundwater and

45 surface water samples sourced from throughout the extensive monitoring well

network of Bribie Island. These samples were collected during the sampling period

of September 2000 to July 2002. This hydrochemical data has been incorporated

with existing data collected by NRM&E and is presented in Appendix H. Harbison

85

(1998) conducted an extensive interpretation of the hydrochemistry of groundwater

and surface water on Bribie Island. However, due to previously limited data

available for the upper unconfined aquifer, new analysis is included here to enable

further characterisation of groundwater and surface water. Average major ion

concentrations of groundwater and surface water are illustrated in Table 12.

Table 12. Average major ion concentrations for groundwater and surface water samples of Bribie

Island

Major cations Major anions

Sample Na+

mg/L

K+

mg/L

Mg2+

mg/L

Ca2+

mg/L

Cl-

mg/L

HCO3-

mg/L

SO42-

mg/L

Water type

Semi-confined

groundwater 47 3 6 5 73 44 7

Na-Cl,HCO3

Na,Ca-

Cl,HCO3

Unconfined

groundwater 25 1 5 2 46 0.5 4

Na-Cl

Na,Mg-Cl

Surface water 30 1 5 3 48 0.07 6 Na-Cl

Na,Mg-Cl

September 9th 2000 to July 30th 2002

6.5.3 Water types

The classification of water types based on the system of Davies and DeWiest (1966)

identifies hydrochemical groupings of water samples from throughout Bribie Island.

These groupings can be related to the source of the sample and aquifer lithology.

The major ions of Na, Mg, Ca, Cl, HCO3 and SO4 are included in the classification

of water types. The tri-linear Piper diagram of Figure 36 illustrates the relative

concentrations of these major ions in % meq/L.

The similarities in ionic chemistry of both unconfined groundwater and surface water

suggest that groundwater-surface water interactions exist. Both surface water and

unconfined groundwater are typically Na-Cl or Na,Mg-Cl water types (Table 12),

and have chemical ratios similar to local rainfall confirming precipitation as the

primary source of recharge. The enrichment of Ca is attributed to carbonate lenses

(remnant shell material) scattered throughout the beach ridge sediments (Figure 36).

Due to the short residence time and low pH of both surface water and unconfined

86

groundwater, bicarbonate (HCO3) concentrations are negligible within these water

bodies.

Relatively limited ion-exchange and weathering processes are evident throughout all

water types on Bribie Island. However, semi-confined groundwater beneath the

indurated sand layer shows signs of enrichment of HCO3. Bicarbonate enrichment

may result from an increased residence time and a possible contribution of

continental water from the weathered sandstone bedrock. Calcium enrichment is

also evident within deeper groundwater and may be a result of similar processes.

Water types for the semi-confined groundwater are typically Na-Cl,HCO3 or Na,Ca-

Cl,HCO3.

Figure 36. Tri-linear diagram of major ion chemistry for groundwater and surface water. Water types

and aquifer lithology relationships are represented by colour coded points. Arrows indicate principle

directions of hydrochemical evolution

87

6.5.4 Organic Carbon Content

Dark coloured surface waters and unconfined groundwater are also distinguished

from deeper semi-confined groundwater by total organic carbon concentrations

(TOC). Total organic carbon of surface waters typically range in concentration from

65-142 mg/L, with an average of 103 mg/L as detailed in Table 13. The unconfined

dark coloured groundwater has TOC concentrations ranging from 55-219 mg/L, with

an average of 108 mg/L. Deeper semi-confined groundwater has TOC

concentrations of 18-83 mg/L, with an average of 35 mg/L.

The acidity contribution of humic substances is equivalent to the A-, carboxylate

anion. Concentration of the organic anion can be estimated for water samples and

good ionic balances (± 6 %) are possible for coloured waters when A- is included as

illustrated in Table 13. Calculation of the organic anion from dissolved organic

matter is tabulated in Appendix I.

Table 13. Average total dissolved organic carbon concentrations and charge balances of water bodies

and the influence of organic acid (A-) concentration

Semi-confined

groundwater

Unconfined

groundwater

Surface water

Element

(meq/L) (meq/L) (meq/L)

Na 2 1.1 1.5

Mg2+ 0.5 0.4 0.5

Ca2+ 0.2 0.07 0.2

K+ 0.08 0.03 0.04

Σ cations 2.78 1.6 2.24

Cl- 2 1.2 1.7

HCO3 0.7 0.01 0

SO42- 0.1 0.05 0.15

A- 0.1 0.4 0.4

Σ anions 2.9 1.66 2.25

Σ cations/

Σ anions 0.96 0.96 0.99

TOC (mg/L) 35 108 103

88

6.6 Aquifer Hydraulic Testing

A range of hydraulic testing methods from single bailer tests to a more complex

assessment of pumping test data is used to confirm the hydraulic properties of the

Bribie Island aquifers. The various tests carried out were conducted on the multiple

depth wells established on the reference transect.

6.6.1 Bailer tests

Most of the thirty bailer tests conducted throughout Bribie Island occurred across the

reference transect as illustrated in Figure 37. Additional wells adjacent to the

transect were tested; however only two wells (114 and 115) could be reliably tested.

Due to the use of manually recording the rising head, some of the tested wells

recovered faster than reliable readings could be taken (eg. 101 and 100).

Additionally, deeper wells such as 089 and 088 were difficult to reliably test due to

their lower initial heads. Typically, within these deeper wells the rising head was

near completely recovered before the manual recorder (“dipper”) reached the water

surface. Of the thirty wells tested only thirteen wells produced reliable results, which

are illustrated in Figures 38, 39, and 40. Wells considered unsuitable for bailer tests

were investigated for their suitability to pumping tests.

Figure 37. Summarised profile across the reference transect D-D' showing wells that were tested by

the use of bailer tests. Two wells (114 and 115) not included on this transect are located to the south

(refer to Figure 16)

Figure 38. Rising head plots derived from bailer tests of wells slotted within the upper foredune and beach sand aquifer. Plots A-I indicate damped conditions89

90

From the reliably recorded bailer tests, three distinct groups of well settings can be

identified based on the time taken for recovery; a) the foreshore and beach sand

aquifer (unconfined), b) the swale deposits and c) the upper shoreface deposits

(indurated sand layer). The rising head plots of Figure 38 illustrate wells slotted

within the upper foredune and beach sands. These wells are slotted within clean

medium grained sand and feature fast recovery rates. The rising head curves follow

consistent trends with most recovery occurring within 10-20 seconds from t0. The

organic rich sands of the central swale deposits (wells 129 and 146) typically show

slower recovery rates as indicated in Figure 39. Significant recovery occurred within

20-40 seconds from t0. The highly indurated sand of the upper shoreface deposits

(wells 143 and 150) have the slowest recovery rates from all tested wells (Figure 40).

Significant recovery greater than 100 seconds was measured in both wells. Results

from all tested wells indicate damped conditions.

Figure 39. Rising-head plots derived from bailer tests of wells slotted within the swale deposits

(organic rich). Both plots A and B indicate damped conditions

91

Figure 40. Rising-head plots derived from bailer tests of wells slotted within the upper shoreface

deposits (highly indurated sand). Both plots A and B indicate damped conditions

6.6.2 Pumping test 1

Pumping test 1 was conducted for 24 hours at a constant pumping rate of 1.2

m3/hour. The purpose of the test was to hydraulically test the semi-confined

92

shoreface brown sand aquifer below the indurated sand layer. Groundwater was

extracted from well 101, while observation wells 139, 140, 141, 142, 143, 088, 144

and 145 were monitored as illustrated in Figure 41. The pumping well slotted

section is located directly below the indurated sands (Figure 27 and 41). Partial

penetration is limited as the slotted section approximately penetrates the entire

sediment thickness between the indurated layer and the sandy silts below.

Figure 41. Vertical cross-section of transect D-D′ showing drawdown results from pumping test 1.

Pumping and observation wells are included. Also indicated are schematic representations of induced

flow from the pumping wells

Figure 42 shows time-drawdown plots of wells 142, 143 and 101. As illustrated in

Figure 41, these nested wells are slotted within differing sedimentary units.

Stratification of the water levels throughout the aquifer is particularly obvious in

pumping test results (Figure 42) as was also shown in the flow net (Figure 33). The

unconfined water table observed within well 142 is located at a height of

93

approximately 7.4 m above MSL and shows no signs of pumping influence.

Observation well 143 is slotted within highly indurated sands and indicates a

hydraulic head at approximately 2.9 m above MSL. Pumping influences are noticed

within the time-drawdown plot for observation well 143. Observation well 143 is the

only well during the pumping test to respond to pumping influence. A drawdown of

approximately 0.05 m was recorded and indicates that some hydraulic connectivity

may exist between the highly indurated sands (aquitard) and the weakly indurated

sands immediately below. The pumped well (101) drawdown was approximately

0.47 m. Conditions of steady state flow were approached.

Figure 42. Response of pumping well (101) and observation wells (142 and 143) to pumping test 1.

Heights of wells above bottom of aquitard are indicated by z


A second pumping test was conducted for a period of 24 hours at a constant pumping

rate of 1.2 m3/hour. The second test extracted water from the offshore sandy silt

94

aquifer (well 088) beneath the shoreface brown sand aquifer. Observation wells 139,

140, 141, 142, 143, 101, 144 and 145 were monitored as illustrated in Figure 43. No

observation wells responded during the test. Drawdown in the pumping well

exceeded 4 m. Partial penetration of the sandy silt aquifer by the pumping well

slotted section may have resulted in non-radial and non-horizontal flow paths.

Placement of the slotted section at the bottom of the aquifer against the weathered

sandstone bedrock may have reduced some of the effects of partial penetration.

Figure 43. Vertical cross-section of transect D-D′ showing drawdown results from pumping test 2.


flow from the pumping wells

Time-drawdown plots of wells 142, 143, 101 and 088 are shown in Figure 44, and

illustrate that pumping influence was not evident within any of the nested

observation wells. Pumping influence was also not observed within wells 140 and

145. These wells are slotted within the same unit as the pumping well 088 (sandy

silts with lenses of clay and fine sand). The inactivity within the wells 140 and 145

95

may have resulted from the effects of partial penetration; however it is more likely

that these observation wells were located outside the cone of depression surrounding

the pumping well. The size and shape of the drawdown curve for pumping well 088

indicates that the surrounding aquifer material has a relatively lower hydraulic

conductivity compared to the material tested in pumping test 1. In addition, the cone

of depression also reached near steady state conditions relatively quickly (<400 min).

A contributing recharge source is unlikely responsible for the steady state conditions

as drawdown was not observed within any of the observation wells located within or

above the tested aquifer.

Figure 44. Response of pumping well (088) and observation wells (142, 143, and 101) to pumping

test 2

96

Additionally, the effects of barometric pressure had to be included within the

analysis of observation well data for the second pumping test. Observation well 101

recorded anomalous readings during the period of pumping as illustrated in Figure

45. The influence of barometric pressure on the water level within well 101 caused

head values to rise and fall during the test. Where the influence of barometric

pressure has been removed, the corrected head values indicate well 101 has not

responded to pumping influences. Barometric efficiency of well 101 approximates

58 % suggesting highly semi-confined conditions for the slotted portion of aquifer

(Table 10). Other nested wells (142 and 143) did not necessitate the removal of

barometric pressure effects, as no effects were evident within their readings.

Figure 45. Influence of barometric pressure is evident in the uncorrected raw water level data for

observation well 101 during pumping test 2. The corrected head shows that well 101 has not been

affected by pumping and the natural drainage rates are low. Barometric efficiency of well 101

approximates 58%

97


The third pumping test was also conducted for a period of 24 hours at a constant

pumping rate of 1.2 m3/hour. The third test extracted water from the deepest section

of the reference transect within the palaeochannel aquifer (well 089). In addition,

observation wells 090, 137, 138, 089, 100, 139, 140 and 141 were also monitored as

illustrated in Figure 46. The third pumping test was a re-run of an earlier abandoned

test where discharge of water proximal to the pumping well resulted in localised

recharge to adjacent unconfined wells. As a consequence, data from the abandoned

test are omitted from the results.

Figure 46. Vertical cross-section of transect D-D′ showing drawdown results from pumping tests 3.


flow from the pumping wells.

98

The time-drawdown plot of the pumping well (089) and observation well (136) is

shown in Figure 47. Well 136 is located approximately 440 m east of the pumping

well and also slotted within the channel deposits (Figure 46). No other observation

wells responded during the test. Drawdown within well 089 was 0.63 m, while

drawdown within observation well 136 was 0.15 m. Partial penetration of the

pumping well is limited as illustrated in Figure 46. However, despite the possibility

of partial penetration of the pumping well, horizontal flow conditions can be

assumed at the observation well as the radial distance to the observation well (r) is

greater than two times the aquifer thickness (b): r > 2b (Kruseman and De Ridder

1979). Additionally, use of small diameter wells should result in negligible well

storage effects.

Neither the pumping well nor the observation well attained steady state conditions.

However, the period of pumping was adequate for steady state conditions to at least

be approached therefore validating the use of analytical solutions such as the Theis

drawdown, and Theis recovery methods. It is also noticed within Figure 47 that

observation well 136 does not approach steady state conditions in the same manner

as the pumping well. It is apparent that the rate of drawdown within the observation

well may not decline as expected during the test. Barrier boundary conditions are

often associated with increased drawdown within observation wells during pumping

testes. Barrier conditions may be present within the palaeochannel sediments due to

the bounding effects of the weathered bedrock. The influence of barrier boundaries

must therefore be taken into account when analysing for aquifer hydraulic properties.

Figure 47. Graph of drawdown verses time for both the pumping well 089 and observation well 136

99

7.0 HYDRAULIC TEST ANALYSIS AND INTERPRETATION

7.1 Bailer Tests

Bailer tests of the foreshore and beach sand unconfined aquifer provide a range of

horizontal hydraulic conductivity (Kh) estimates of 11-4.4 m/day with an average Kh

estimate of 6 m/day (Table 14). Additionally, an estimate of specific yield of 0.25-

0.30 for the medium-fine grained sand aquifer can be adapted from the literature

(Fetter 1994; Laycock 1975; Aschenbrenner 1996). Also notable are the hydraulic

conductivity estimates for the shallow organic rich sands that occur within the central

swale. The Kh estimates for the swale deposits range between 1-3 m/day (Table 14).

Table 14. Hydraulic conductivity values determined from bailer tests

Well

Elevation a

(m.a.s.l) Depth a (m)

Length of

slots (m) K b (m/day) K c (m/day)

Foreshore and beach sand aquifer (unconfined)

114 1.2 4.5 1 11 9

115 1.8 4.0 1 5.6 4.4

126 2.9 3.5 1 7.9 5.2

137 2.5 1.7 3 5.8 4.3

138 2.5 3.3 3 7.7 9

139 2.4 4.2 3 5.7 4.3

142 5.0 3.2 3 6.0 6.2

145 2.3 1.7 3 6.8 6.7

149 2.8 2 3 4.4 4.3

Organic rich sand (swale deposit)

129 -0.2 3.6 1.5 2.9 1.6

146 1.2 2.5 3 1.8 1.2

Indurated sand Layer (aquitard)

143 -0.5 8.5 3 0.09 0.12

150 -0.7 5.5 3 0.25 0.20

a midpoint of slots c Mean values from Hvorslev (1951) analysis

b mean values from Bouwer and Rice (1979) analysis

Based on bailer testing, the highly indurated sand profile has an estimated Kh with an

order of magnitude less (0.09 m/day and 0.25 m/day) than the overlying dune sands.

Plots of recovery data versus time illustrate two examples from each lithological

grouping (Figure 48).

100

Figure 48. Examples of bailer test results from the lithological groupings; A) foredune and beach

sand aquifer, B) organic rich sand of the swale deposits, and C) the indurated sand layer

An average Kh of 0.17 m/day for the indurated sand layer is not insignificant. If this

figure of Kh translates to vertical hydraulic conductivity (Kv), significant vertical

leakage may occur despite the reduced porosity and permeability of the indurated

sand layer. Therefore, the elevated groundwater heads observed across Bribie Island

may be a result of significantly reduced Kv within the indurated sand layer.

101

Inspections of drill core samples indicate induration is highly variable over short

vertical distances. Bailer testing within the indurated sands may neglect the

influence of these layers, particularly where they are thin and interposed with layers

of moderate Kh.

Head gradients are significantly increased within, and above, the indurated sand layer

(Figure 33). Vertical head gradients can be used to gain estimates of Kv based on the

Darcian flow equation:

KAiQ −= refer to (1)

The equation can be rewritten when annual recharge (W) is in one dimension:

KiW = (14)

Where;

W = Recharge (L)


i = Hydraulic gradient (dimensionless)

Vertical head gradients are taken from the nested observation wells 142, 143, 101

and 088 (Figure 33). The hydraulic head gradients are illustrated in Table 15.

Table 15. Analysis of vertical head gradients of nested wells 142-088 via Darcy’s law. Vertical

hydraulic conductivity (K m/day) is estimated for each section of aquifer separated by the nested

wells. Estimated K values are generally much lower than provided by bailer tests and pumping tests

142-143 143-101 101-

088 142-

088 units

When recharge (W)

= 5.6-4 5.6-4 5.6-4 5.6-4 m/day

Let gradient = 4 1 0.02 5 m head difference between slots 5.3 7.5 21 33.8 m vertical distance between slots Hydraulic gradient

(i) 7.5-1 1.3-1 9.5-4 1.5-1 dimensionless

Estimated K

(m/day) 7.3-4 4.1-3 5.7-1 3.7-3 m/day

Rainfall (R) = 1300 mm/year

Evapotranspiration (ET) = 1100 mm/year Refer to section 3.6 (Bubb and Croton

2002)

Recharge (W = R - ET) = 200 mm/year

= 0.00056 m/day

102

Substitution of the hydraulic head gradients and a value for recharge into the Darcy

flow equation results in estimates of vertical hydraulic conductivity as illustrated in

Table 15. Estimated Kv of the highly indurated sand is approximately between

0.0007 m/day and 0.004 m/day. These estimated values of Kv are on average two to

three orders of magnitude less the Kh estimates for the same unit determined via

bailer test methods. In addition, the estimates displayed in Table 15 also illustrate

that the upper portion of the highly indurated sands has the lowest Kv estimate.

Physical observation of well logs confirms the section between observation wells 142

and 143 is the most highly indurated. The Kv of the highly indurated sands is also

two to three order of magnitude less than the sand silt material between observation

wells 101 and 088, confirming the indurated sands as a leaky aquitard.

7.2 Pumping Tests

Recovery analysis of pumping well data and drawdown analysis of observation well

data produce the hydraulic conductivity estimates listed in Table 16.

Table 16. Hydraulic conductivity (K) and specific storage (Ss) values determined from pumping tests

Test Well Stratigraphic Unit Kh Ss

(m/day) (Dimensionless)

1 101a Upper/lower shoreface deposits - weakly indurated

brown sands

25† -

2 088a Offshore deposits - sandy silts with lenses of clay and

fine sand

1† -

3 089a Channel deposits - medium sand (lenses of fine and

coarse sand)

7† -

3 136b 6* 4.5 x 10-6

3 136b Channel deposits - medium sand (lenses of fine and

coarse sand)

7‡ 3.5 x 10-6

3 136b 5• 9.7 x 10-6

a Pumping well

b Observation well

† Theis recovery method

* Theis drawdown method

‡ Cooper-Jacob straight line method

• Stallman method

103


Theis Recovery analysis of pumping well 101 slotted within the shoreface brown

sand aquifer (Figure 49) estimates horizontal hydraulic conductivity as 25 m/day

(Table 16). An estimate of storativity cannot be calculated due to the absence of

drawdown in observation wells located within the same unit.

Maximum drawdown within the pumped aquifer was approximately 0.5 m, while

maximum drawdown within the overlying highly indurated sand profile (well 143)

was approximately 0.05 m as illustrated Figure 42. Observation well 143 is located

at a radial distance of 3 m and vertical distance of 1.5 m from the pumping well 101.

Assuming the indurated sand layer provides a degree of confinement to the pumped

aquifer, flow to the pumping well is assumed to be horizontal within the aquifer and

vertical within the overlying indurated sand aquitard (Kruseman and De Ridder

1979).

Figure 49. Analysis of recovery data from pumping test 1, well 101, with the Theis recovery method

Pumping tests with observation wells in the aquitard have often been used to obtain

reliable estimates of vertical hydraulic conductivity within an aquitard (Neuman and

Witherspoon 1972; Rodrigues 1983; Keller et al. 1986; Neuman and Gardner 1989).

The tests rely on measurement of head changes within the aquitard induced by

changes of head in an underlying or overlying aquifer (van der Kamp 2001). The

method developed by Neuman and Witherspoon (1972) applies the ratio between

drawdown within the aquitard against drawdown within the aquifer to a set of type

104

curves. The theoretical analysis is based upon one-dimensional diffusion of pressure

transients into a uniform homogeneous aquitard (van der Kamp 2001).

The Neuman and Witherspoon (1972) ratio method yields values of hydraulic

diffusivity (Kv/Ss), hence to obtain a value for Kv for the indurated sand aquitard, an

independent estimate of Ss is required. Laboratory values of Ss are generally used in

such situations. However, values obtained via laboratory analysis often do not

approximate in situ conditions (van der Kamp 2001). An estimate of Ss for the

indurated sand layer is not available. However, Ss may be considered very low due

to the predominately sandy matrix of the indurated layer.

Additionally, the careful set-up of the pumping test is also necessary to provide

reliable values. It is recommended that observation wells in the aquitard be placed at

a radius of several aquifer thicknesses away from the pumping well (Neuman and

Witherspoon 1972). At this distance the effects on drawdown due to strain and

deformation within the aquitard are greatly reduced. This effect is termed the

“Noordbergum effect” and can induce anomalous changes in head near the well at

the beginning and end of pumping (Rodrigues 1983; Hsieh 1996; Burbey 1999; van

der Kamp 2001). Unfortunately, as noted above, the placement of the aquitard

observation well 143 is less than the required distance from the pumping well.

Observation wells placed in the aquitard close to the pumping well may also be

susceptible to leakage through the annulus around the casing of the pumping well.

Therefore, the annulus around the casing should be properly sealed to prevent

leakage. The pumping well 101 has no such seal suggesting that leakage is highly

likely. The resulting drawdown within the observation well located in the overlying

aquitard may be very misleading and should therefore be considered with caution.

Despite the limiting factors noted above, the hydraulic character of the highly

indurated sand layer (aquitard) can be determined. The recovery of heads in the

brown sand aquifer and the indurated layer display no comparable time lag.

Therefore, a negligible storage term exists for both units. This is not surprising as

both units have a dominantly sand composition, thus reducing the likelihood of

matrix compressibility.

105

Water level drawdown for observation well 143 (s′) and pumping well 101 (s) were

measured from the hydrograph illustrated in Figure 41. A drawdown ratio (s′/s) of

0.076 was determined at time 58 min. Values to determine hydraulic diffusivity

(Kv/Ss), were derived from ratio-method type curves provided by Neuman and

Witherspoon (1972). The storativity of the aquifer was assumed to be low at 1x10-5,

however the influence of aquifer storativity on overall results is negligible.

Hydraulic diffusivity (Kv/Ss) of the highly indurated sand aquitard is estimated at

2.7x102 m2/day, which is more than 6 orders of magnitude less than Kv/Ss for the

pumped shoreface brown sand aquifer at 2.5x108 m2/day. Due to the uncertainty of

Ss of the indurated sand aquitard, a range of specific storage is proposed from 1.0x10-

4 to1.0x10-6. Therefore, based on the Neuman and Witherspoon (1972) ratio method

an estimate of Kv for the indurated sand aquitard may range between 2.7x10-1 m/day

and 2.7x10-3 m/day.


Due to the silty composition of the offshore deposits, these deposits have a lower

hydraulic conductivity (Kh) compared to the shoreface sand aquifer located above.

Figure 50 illustrates a Theis Recovery plot generated from residual drawdown data

collected during the second test. Theis recovery analysis of pumping well 088

estimates hydraulic conductivity as 1 m/day (Table 16). An estimate of storativity

cannot be calculated due to the absence of drawdown in observation wells located

within the same unit.

Figure 50. Analysis of recovery data from pumping test 2, well 088, with the Theis recovery method

106


Drawdown data from observation well 136 for the period between 120 min and 460

min match the Theis type curve (Figure 51). Typically, initial results are often not

closely represented by the Theis theoretical drawdown curve equation and so less

weight should be placed upon these readings (Kruseman and De Ridder 1979).

Therefore, late time data is typically used as a more reliable indication of aquifer

conditions.

For the period between 120 min and 460 min the match between measurements and

the Theis type curve indicate values of:

Hydraulic conductivity (K) = 6.06 m/day

Aquifer thickness (b) = 9 m

Transmissivity (T) = 54.4 m2/day

Storativity (S) = 0.000041

Deviation of late time data from the Theis type curve suggests an increase in

drawdown during the latter stages of the test. Changes in the shape of time-

drawdown curves after initial fitment to the Theis type curve are often associated

with barrier boundary conditions.

Figure 51. Matching of data from pumping test 3 of observation well 136 to the Theis type curve.

Early time data after 120 min fit the Theis type curve; however deviation from the curve during late

time data may suggest barrier boundary conditions

107

The assumption that aquifers are of infinite areal extent is typically used solely for

mathematical convenience. However, aquifers are always bounded by geological

features such as faults, bedrock contacts, facies changes and also recharge areas such

as streams and lakes. As a result it is typical for some boundary effects to impact on

well hydrographs. When the cone of depression reaches an impermeable boundary,

the drawdown within the area of influence has to increase to produce the same

amount of discharge because of no inflow from the boundary.

The influence of barrier boundary conditions can also be illustrated when drawdown

data are analysed by the Cooper-Jacob straight line method. The well function (W(u))

of the Theis equation can be modified to a logarithmic term when u is < 0.01 (Weight

and Sonderegger 2001). Values of u greater than 0.01 can create errors. The Theis

equation can be rewritten:

=

SrTt

TQs 2

25.2log4

3.2π

(15)

Where;

s = Drawdown (L)

S = Storage (dimensionless)

T = Transmissivity (m2/day)

t = Time (t)


When drawdown data from an observation well are plotted versus time the results

fall along a straight line (under confined conditions). If barrier conditions are present

and have influenced the drawdown data, the slope of the line will double as a result

from the increased drawdown as illustrated in Figure 52. The initial slope of the

early time data can be used to calculate aquifer properties before barrier boundary

conditions prevail.

Using the Cooper-Jacob method the data for the period between 120 min and 460

min indicate values of:

108



Transmissivity (T) = 68 m2/day


Additionally, as time approaches the “inflection point” the data indicates apparent

leakage (Figure 52). This leakage may be attributed to a differential drainage

process. The channel deposits include lenses of fine sand, coarse sand and gravel, all

of which may drain at comparably different rates resulting in some limited recharge

to the drawdown data.

Typically, the effects of more than one barrier boundary are observed at later time

periods. Figure 52 illustrates the development of a possible third slope prior to the

end of the pumping period. With continued pumping this data may have been

evaluated with more certainty.

Figure 52. Cooper-Jacob plot from pumping test 3 of observation well 136. Straight line behaviour in

drawdown versus time exists until t = 460 min. Increased drawdown results from barrier boundary

effects

The effects of barrier boundaries can be simulated by the addition of image wells in

conjunction with the principle of superposition. The introduction of image wells

109

transforms the system to one that can be analysed by use of pre-established flow

analyses. For each barrier that is encountered during the pumping period an image

well must be included (Kruseman and De Ridder 1979). When one barrier is

uncounted, only one image well need be included within the analysis as illustrated in

Figure 53. The position of the image well reflects the position of the real pumping

well. However, the image well is located on the other side of the barrier and at right

angles to it (Fetter 1994). For barrier boundaries, the image well discharges at the

same rate as the real pumping well. The combined drawdown of the two wells

approximates the effect of the barrier boundary. The actual drawdown is the sum of

the drawdown from the real well and the drawdown from the image well (Figure 53).

Figure 53. Schematic cross-section and plan of an aquifer with a straight barrier boundary, A) natural

conditions, B) equivalent system with an image well, C) plan (after Kruseman and De Ridder 1979)

110

Well functions of both the real well and the image well are expressed:

,4

2

TtSru =

TtSr

u ii 4

2

= (16)

Therefore, the flow equation for a system that includes barrier effects can be

expressed as:

)(4

)(4 iuW

TQuW

TQ

ππ+= (17)

)]()([4 iuWuW

TQ

+=π

(18)

Where;

u = Well function of real well (dimensionless)

ui = Well function of image well (dimensionless)

r = distance between the observation well and the real pumped well (L)

ri = distance between the observation well and the image well (L)

T = Transmissivity (m2/day)

t = Time (t)

S = Storage (dimensionless)


In addition, the use of a drawdown versus time graph such as the Cooper-Jacob plot,

the distance, ri, between the observation well and the image well can be calculated.

As illustrated in Figure 54, a drawdown value (s1) is selected from the period where

the boundary effect is not evident. The time of this value is recorded as t1. On the

second segment of the time-drawdown data where the boundary effect prevails, the

time (t2) is recorded where the drawdown (s2) is equal to the initial drawdown value

(s1). These values are then substituted into the flow equation as illustrated below.

111

Figure 54. Cooper-Jacob plot of drawdown versus time. The distance of ri can be calculated when the

values of s1 at t1 and si at t2 are calculated and substituted into the flow equation

Since s1 at t1 equals s2 at t2:

=

2

2

1

2

4444 TtSrW

TQ

TtSrW

TQ i

ππ(19)

2

2

1

2

44 TtSr

TtSr i= (20)

2

2

1

2

44 TtSr

TtSr i= (21)

2

2

1

2

tr

tr i= (22)

Therefore, when:

830100440 22

ir= (23)

8301268

100440 22

= (24)

1268=ir m distance from observation well to image pumping well

However, to find the exact location of the image well at the radius of ri, at least three

observation wells are required. The position of the boundary can then be calculated.

112

In the case of Bribie Island the established depth to bedrock contours give an

approximate position of the barrier boundary. This approximate location of the

barrier boundary has been included within the schematic illustration of Figure 55.

Since analytical solutions have been developed for the drawdown distribution in a

confined aquifer with infinite lateral extent, these solutions can also be adapted to

include bounded aquifers. Stallman’s method, as described by Kruseman and De

Ridder (1979), enables the evaluation of aquifer properties from the portion of data

that has resulted from the increased drawdown associated with a barrier boundary.

The type curve method relies upon the matching of data points obtained during the

pumping test to a series of type curves. This method can be applied if the following

limiting conditions are satisfied (Kruseman and De Ridder 1979):

1. all limiting conditions that apply to the Theis method, and

2. within the zone influenced by the pumping test, the aquifer is crossed

by one or more straight fully-penetrating recharge or discharge

boundary.

The ratio of ri/rr = β, is used to identify the appropriate type curve for best fit of the

data. The numerical values of the well function of the Stallman type curve

W(u,β1→n) are typically given within published references such as Kruseman and De

Ridder (1979). In cases where one boundary exists there are only two terms: the

term (Q/4πKb) W(u) describing the influence of the real pumping well and the term

(Q/4πKb) W(β2u) describing the influence of the image well.

KbtSru r

4

2

= , uKb

SrTtSru ri

i2

222

44β

πβ

=== (25)

One straight barrier, as illustrated in Figure 55:

{ })()(4

2uWuWKb

Qs βπ

+= (26)

),(4

βπ

uWKb

Qs B= (27)

113

Figure 55. Schematic cross-section of transect H-H' indicating location of pumping well 089 and

observation well 136. Both wells are located within the deepest part of the palaeochannel. The

weathered sandstone bedrock results in barrier boundary conditions during pumping of adjacent wells

114

Using the Stallman method (Figure 56) data for the period after 460 min indicate

values of:



Transmissivity (T) = 47.5 m2/day


Figure 56. Curve fit of late time data (>494 min) from observation well 136 to the Stallman type

curve (β = 3)

115

8.0 DISCUSSION

8.1 Comparison of Hydraulic Conductivities

Previous investigations of the hydraulic properties of the Bribie Island aquifers have

focused on the southern section of the island in relation to water supply management

options (Lumsden 1964; Ishaq 1980; Isaacs and Walker 1983). Morphology of the

Holocene dune system in the south of the island differs from the northern Pleistocene

dune system. Both sandy silt sediments and indurated sand development are not as

extensive in the younger sediments. Therefore, aquifer heterogeneity has not been

considered a key component in previous hydrogeological investigations.

Laboratory testing of sediments by Harbison (1998) provide estimates of hydraulic

conductivity for sediments taken mostly from the southern section of the island.

Table 17 has been adapted from Harbison (1998) and illustrates the large range of K

values that have been estimated for Bribie Island.

Table 17. Summary of previous estimates of hydraulic conductivity for Bribie Island and North

Stradbroke Island using grain size analysis, pumping tests, tidal damping, falling head tests and water

balance analysis (after Harbison 1998)

Hydraulic Conductivity, K (m/day) Author Grain size

analysis

Pumping test/

Tidal damping †

Laboratory hydraulic test/

Water balance analysis ∗ Lumsden (1964) 13 - 4 Laycock (1975) 15 6 0.09–155 John Wilson and Partners (1979) - 15–75 13-30 ∗ Ishaq (1980) 17 - - Harbison (1998) 25 a 1-8† 9 a, 0.4–0.8 b a foreshore and beach sand aquifer (unconfined aquifer) b indurated sand layer (aquitard)

Grain size analysis and laboratory hydraulic tests are likely to produce erroneous

results for effective porosity and hydraulic conductivity due to the disturbance of

samples during removal and relocation (Todd 1959; Fetter 1994). However,

laboratory estimates are a useful means to provide a check on results obtained via

other methods. It was noted by Harbison (1998) that falling head tests were

conducted at a much higher hydraulic gradient compared to field conditions. Elution

116

of fines from the sample during the falling head tests may be attributed to the high

hydraulic gradient during the tests. It is therefore suggested that the K estimates of

Harbison (1998) may be over-estimated.

In addition, laboratory testing limits the spatial integration of K to a very small scale

(Millham and Howes 1995). Therefore, in situ hydraulic testing such as tidal

response, bailer tests and pumping tests should be considered more reliable methods

for the estimation of aquifer properties.

Obtaining satisfactory results from pumping tests on sand islands is complicated by

the required long pumping times and the disposal of extracted water. In 1979 John

Wilson and Partners (unpublished data) conducted two pumping tests in the southern

section of Bribie Island and the estimates of hydraulic conductivity varied between

15 m/day to 75 m/day (Table 17). These high K estimates may be due to errors

attributed to the short duration of pumping (8 hours). Also, the results may reflect

the differences in sedimentary material between the south and the north of the island.

In addition, Laycock (1975) conducted six pumping tests on the neighbouring mega-

dune sand island, North Stradbroke Island (NSI). The results of these pumping tests

indicate an estimate of hydraulic conductivity of 6 m/day (Table 17), reflecting the

results of the unconfined aquifer of Bribie Island. Indurated sand development and

preservation within the massive dune sands of NSI is less extensive than for Bribie

Island. As a result, only localised perching of groundwater exists on NSI. Laycock

(1975) noted that the form of the log-log drawdown curve typically fit well for the

unconfined conditions. The delay in yield to the water table was considerable; the

return of the drawdown log-log curve to the Theis equilibrium curve did not occur

during even the longest test of 12 days. The specific yield determined using Boulton

curves approaches the value of 0.2.

Laboratory hydraulic tests of sediment similar to Bribie Island have also been

analysed by Acworth and Dasey (2003). Laboratory tests of the coastal barrier

sediments, from the coastline of New South Wales, Australia, indicate a significant

difference between the fine sand aquifer and a poorly cemented indurated sand layer.

From grain size analysis the hydraulic conductivity of the fine sand aquifer was

117

estimated at 20 m/day. Additionally, minimally disturbed core samples of the poorly

cemented indurated sand gave estimates of 2 m/day (Acworth and Dasey 2003). As

with Harbison (1998), the estimates of Acworth and Dasey (2003) may also be over-

estimated due to errors resulting from the method of testing.

Examples of pumping tests within similar physical settings to Bribie Island are

available in the literature (i.e. Harris 1967; Burkett 1996; Suresh Babu et al. 2002),

and are summarized in Table 18. The estimates of hydraulic conductivity obtained

from these pumping tests agree well with the values determined for the aquifers of

Bribie Island. Of particular note are the estimates of Anderson et al. (2000) for

Hatteras Island, North Carolina. Extending from the results of the pumping tests by

Burkett (1996), numerical solutions were developed to simulate observed elevated

water table levels across the sand island. In order to achieve a satisfactory

simulation, the numerical model focused on the hydrogeologic framework of the

sand island and incorporated regional heterogeneities. What was termed a “buried

wetland” produced significant influence on the surrounding water table observations.

Similar to Bribie Island, the relatively high permeability of the North Hatteras Island

aquifers may also exacerbate the significance of the heterogeneities. Numerical

solutions estimated a hydraulic conductivity of 0.05 m/day for the low permeability

material. Anderson et al. (2000) concluded that this heterogeneity was responsible

for the elevation of the water table, however, did not indicate whether this material

could also act as a confining layer.

Table 18. Comparative estimates of hydraulic conductivity (K) for characteristically similar sand

masses/islands

Author Hydraulic cond.,

K (m/day) Sediment type

Harris (1967) 5 Fine-medium sand, moderately-well sorted Burkett (1996) 21 Medium-coarse sand, lenses of shells Anderson et al. (2000) 25 a, 12.5 b, 0.05 c a Medium-coarse sand, b Fine sand-silt, c buried Suresh Babu et al. (2002) 11 Very fine-fine sands Acworth and Dasey (2003) 20 a, 2 b a Fine sand well sorted, b poorly indurated sand

118

8.2 Conceptual Hydrogeological Framework

This study of Bribie Island demonstrates how detailed measurement of stratigraphy,

groundwater levels, rainfall, barometric pressure and hydraulic testing can be used in

conjunction to identify and assess aquifer heterogeneity within a sand island

environment.

The stratification of water levels across the reference transect and the relatively flat

piezometric surface are in contrast with the classical “domed” water table aquifer

expected of a barrier island (Harris 1967; Vacher 1988; Collins and Easley 1999).

Stratified head gradients through the Bribie Island aquifers suggest groundwater

migration to depth is impeded by the indurated sand layer. An elevated shallow

water table results from the mounding of water above the indurated sand layer. The

indurated sand layer is extensive across the reference transect.

Seepage of fresh unconfined shallow groundwater over indurated sand layers onto

beach faces has been observed in numerous locations on the island. Additionally,

lateral drainage also occurs beneath the indurated layer. The basal groundwater

discharge is generally sufficient to restrict saltwater encroachment and a measurable

freshwater-saltwater interface exists off the coastline around the perimeter of the

island (Harbison 1998).

The shallow unconfined water table aquifer responds rapidly to rainfall events, while

aquifers located beneath the indurated sand layer show a delay in recharge of up to

48 hours (Harbison 1998). Vertical leakage through the indurated sand layer

recharges basal aquifers.

Wells slotted immediately beneath the indurated sand layer indicate high barometric

efficiencies (up to 58 %). Confined aquifers typically measure barometric

efficiencies of 40-70% (e.g. Clark 1967; Davis and Rasmussen 1993; Rasmussen and

Crawford 1997). The “skin effect” shown by well 100 is attributed to a greater

proportion of finer grained sediment within the brown sand aquifer matrix. Wells

slotted within the sandy silt (088) and palaeochannel aquifers (089) have reduced

responses to barometric pressure. Despite low barometric efficiencies, the deep

119

wells do not show rainfall responses typical of the unconfined aquifer. Therefore it

is suggested that the barometric efficiency of these wells is masked by a large skin

effect; rather than connected to the shallow unconfined aquifer system.

It is important to acknowledge the limitations of the pumping tests. Inability to

hydraulically stress the system sufficiently to induce drawdown in nearby

observation wells creates difficulties in assessing hydraulic properties. However,

pumping tests were able to confirm general hydrogeological concepts in regard to

aquifer heterogeneity across the reference transect. The indurated sand layer is not

impermeable. However, the porosity and permeability of the indurated sand layer is

reduced compared to the surrounding aquifers.

Estimates of vertical hydraulic conductivity of the indurated sand layer have been

calculated via hydraulic testing and vertical head gradients. The differing methods

produce estimates of Kv that fall within a broad range. Despite the range of estimates

it is noted that Kv is typically two to three orders of magnitude less than the values

derived for Kh.

The groundwater resource of Bribie Island is of commercial and environmental

importance. Extensive pine plantations tap the shallow unconfined groundwater

table while discharge of groundwater supports extensive estuarine and wetland

habitats. Potable water, principally for domestic use, is currently extracted from the

sand aquifer in the populated south of the island via a trench system, and a well field

is under consideration for the central section of the island.

The quality of the extracted groundwater on Bribie Island has occasionally been

reduced due to elevated iron, manganese, organic content, nutrient discharge and

salinity (Harbison 1998).

Fresh groundwater typically flushes saline water from permeable zones more rapidly

than from low permeable zones. It is therefore possible that within some areas,

excessive groundwater extraction may lead to more than one freshwater/saltwater

water interface in the vertical section as illustrated in Figure 57. Variable

freshwater/saltwater water interface relationships have been reported for other barrier

islands where aquifer heterogeneity is prominent. The island aquifers of Grand Isle,

120

Louisiana, USA, and Assateague Island, Maryland, Virginia, USA, are examples

where variations in hydraulic conductivity and permeability exist (Bolyard et al.

1979; Collins and Easley 1999).

There are no legislated restrictions for extraction of groundwater on Bribie Island,

which allows uncontrolled use of groundwater and a lack of coordination between a

range of users and interest groups. There is a need for effective management

practices to assure continued availability of good quality groundwater on the island.

Figure 57. Conceptual hydrogeology of Bribie Island including aquifer heterogeneity and the main

types of use

121

9.0 CONCLUSION

A summary of the main findings from this study is as follows:

• The stratigraphy of Bribie Island consists of sediment profiles with distinctive

hydraulic characteristics. Hydraulic tests performed across a central

reference transect confirm aquifer heterogeneity and quantify aquifer

parameters such as hydraulic conductivity and specific storage. The

heterogeneities within the stratified aquifer conceptual model have profound

effects on groundwater occurrence and flow within the island.

• Aquifer heterogeneity resulting from the stratification of island sediments can

produce a complex hydrological system as identified within Bribie Island.

Such variations in hydraulic conductivity are very important in controlling

groundwater levels, groundwater migration and groundwater chemistry

through a sand island environment.

• Consistent differences in ionic chemistry exist between “black” and “white”

waters. The wetlands and shallow groundwater are typically “black water”

with low pH values and high organic anion concentrations. The basal

aquifers contain “white water” with near neutral pH and low organic anion

concentrations.

• A laterally extensive indurated sand layer at shallow depth is observed in drill

hole correlations and hydraulic test data. Hydraulic tests confirm that the

indurated sand layer has a significantly reduced permeability that restricts the

downward migration of shallow groundwater; resulting in elevated water

tables and shallow lateral drainage.

• The groundwater beneath the indurated sand layer occurs under semi-artesian

conditions resulting in a shallow hydraulic gradient across the island.

122

Hydraulic conductivity within the basal aquifer beneath the indurated sand

layer is considered moderate.

• Connectivity between the overlying indurated sand layer and the basal

aquifers suggests the indurated sand layer acts as an aquitard reducing the rate

of recharge to the basal aquifer. The basal aquifers exist in a semi-confined

state.

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Appendices

Section A: Associated publications

Appendix A

Chemical character of surface waters on Bribie Island: a preliminary

assessment. (extended abstract)

Presented: PASSCON 2000, Pumicestone Passage and Deception Bay Catchment

Conference, QUT, November 2000

Appendix A – Passcon Conference extended abstract

Chemical Character of Surface Waters on Bribie Island:

A Preliminary Assessment

TIMOTHY ARMSTRONG

School of Natural Resource Sciences, Queensland University of Technology, Brisbane, QLD

INTRODUCTION

Bribie Island is a large barrier sand island in northern Moreton Bay approximately

65 km north of Brisbane. Bribie Island is the eastern boundary of the

Pumicestone Passage catchment and is separated from the mainland by the

shallow estuarine wetlands of the passage. Over the past few decades the entire

catchment, including Bribie Island, has experienced very rapid growth in terms of

urbanisation and agricultural development. While urban development is restricted

to the southern extent of the island, pine plantations and National Park occupy the

northern two thirds of the island.

The assessment of surface waters on Bribie Island is of particular importance due

to the size of the catchment area, the activity on the island and most importantly

runoff into the passage. Bribie Island has four major surface water outlets that

drain into Pumicestone Passage. Most of the water from these creeks originates

from areas that drain pine plantations and National Parks.

This paper provides a brief overview and evaluates the present conditions related

to natural surface water chemistry, distribution and interactions it has with other

processes on the Island. This description of surface waters is part of a larger study

investigating the shallow hydrogeology of the forested areas, and does not

consider the populated southern quarter of the island.


PHYSICAL SETTING

Bribie island has very low relief with a mean elevation of 5 m and a maximum

elevation of 17 m above sea level. The island consists predominantly of two

successive beach ridge systems separated by a major swale (interconnected low-

lying melaleuca swamps) extending through the long axis of the island. The

central swale is the dominant drainage feature on the island. Pine plantations are

generally restricted to the two major beach ridge systems.

The sediments of Bribie Island consist of Quaternary aeolian sand deposits. The

two major beach ridge systems are aligned to the current coastline and represent

sedimentation during Pleistocene interglacial periods (Harbison, 1998).

Sediments are composed of fine to medium grained sands deposited by prevailing

south-east winds.

Contained within the beach ridge sediments is a layer of indurated sands at an

approximate depth of 5-6 m and has a maximum thickness of 9 m. While the

indurated sand (coffee rock) has a reduced permeability that affects water

movement, it comprises a significant volume of the aquifer (Harbison & Cox,

1998).

Due to the reduced permeability of the coffee rock, it acts as a partial confining

layer for the groundwater beneath it. A perched water table results as recharge

(rainfall) is unable to percolate easily through the coffee rock layer. This shallow

water table is directly related to the surface waters.

Methods

Surface water monitoring of 19 sites has consisted of monthly infield testing of

physico-chemical parameters over the past three months. During one round,

water samples were collected for laboratory analysis of major cations and anions,

metals (Fe, Al, and Mn), and nutrients (NO3, PO4).


The present sampling program has also been aided by the compilation of data

from outside sources such as HLA Envirosciences Pty Ltd. and Department of

Natural Resources.

Transects across the island have been established that tie in with the existing bore

network. Early in 2001 an extensive shallow bore network will be developed

along these transects.

RESULTS

Surface water distribution and drainage:

Most surface waters on Bribie Island occur naturally in low-lying depressions

ranging in size from meters to tens of meters in area. These local low points

occur as minor swales forming between minor ridges that are contained within the

larger ridge system. In several coastal locations there are small lakes, which

sometimes are breached during storms. The other major form of surface water on

the island is man-made fire fighting dams. Due to their depth, some dams act as

windows into the shallow groundwater. These windows contribute greatly to the

permanent surface water supply

Organic silts and clays are transported into these depressions where upon settling

can create a type of seal that reduces the infiltration of the surface water

(Harbison, 1998). For this reason surface water can remain in lows for a period of

several weeks after significant rainfall.

The drainage patterns on Bribie Island are ill defined. The most significant flows

are from the two major beach ridge systems into the central swale. In general the

central swale has a northerly flow discharging into Pumicestone Passage via

Westerways Creek in the north of the island. The southern portion of the central

swale flows to the south and discharges into the passage via Wright’s Creek.


Physico-chemical Parameters:

The pH of surface waters on Bribie Island is generally low. The pH range for most

surface waters is between 2.9-4.5 (average pH ≈ 3.6), hence the majority of

surface waters on Bribie Island can be classified as acidic waters. The few

exceptions are saline waters of the coastal lagoons and tidal creeks that have a

typical pH > 6.

The cause of these acidic surface waters on Bribie Island can solely be attributed

to organic acids. Rainfall events flush organics and humic substances into surface

water depressions, where over time organic matter will percolate down to the

shallow water table. Decomposition of the organic matter eventually produces the

organic acids found in these waters, such as fluvic acid (Drever, 1997). However,

the exact chemical type of acid has not yet been determined. In some sites

contribution to low pH may also be related to carbonic acids.

The obvious colour of surface waters can also be attributed to humic substances,

and these waters are often referred to as “black water”. The colour of these Bribie

Island waters is therefore due to the colour of the acid-soluble organics and

particulates in the water and not a staining due to oxidation of metals such as iron.

Most of the surface waters on Bribie Island are exceptionally fresh. The

conductivity ranges from 20-500 µS/cm, while rainfall in this area is typically 20-

40 µS/cm. There seems to be no apparent trend to conductivity distribution,

except for surface water contained in coastal lagoons.

The coastal lagoons along the east coast of the island have conductivities as high

as 44000 µS/cm (similar to the conductivity for sea water). In this study only two

sites with saline waters were analysed, Mermaid Lake and Wright’s Creek. As

these saline samples are not entirely representative of the area, these records are

not included in most averages.


Ionic Chemistry:

The surface waters on Bribie Island typically have a Na,Mg-Cl water type (Group

1, Figure 1). Similarly, shallow groundwaters have a dominant water type of

Na,Mg-Cl. The more saline waters and some surface waters however, have a

water type closer to Na-Cl, reflecting chemical ratios similar to local rainfall and

seawater.

Most surface waters and shallow groundwaters generally show Ca enrichment

with one particular sample showing significant increases in Ca (Figure 1).

Enrichment of Ca may be attributed to carbonate fragments (remnant shell

material) scattered throughout some of the sediments. The enriched samples have

a water type of Na,Ca-Cl. There also appears to be two distinct groups of surface

waters characterised by their Ca concentrations (≈ 1-2 mg/L and ≈ 4-6 mg/L).

80 60 40 20 20 40 60 80

20

40

60

80 80

60

40

20

20

40

60

80

20

40

60

80

Ca Na HCO3 Cl

Mg SO4

Deep groundwaterShallow groundwaterBribie Island rainSurface waterAverage seawater

Group 1

Group 2

Group 3

Surface water &Shallow groundwater

Deeper groundwaters& some surface water

Deep Groundwaters

Na,Mg-ClNa-Cl

Na-Cl-HCO3Na,Ca-Cl-HCO3

So4enrichm

ent

HCO3 enrichmentCa enrichment

Origin of Sample

Na,Mg-ClNa-Cl

Figure 1. Trilinear diagram of major ion chemistry for surface waters and

groundwaters.

Due to the low pH of the surface waters on Bribie Island and the character of local

rainfall HCO3 concentrations have been drastically reduced, with most surface

waters containing nil HCO3 (Group 1, Figure 1). HCO3 enrichment is therefore

restricted to mostly deeper waters that lie underneath the coffee rock layer where

there is a corresponding higher pH level (Groups 2 & 3, Figure 1).


Sulfate concentrations are generally low for surface waters (average. ≈ 5.5 mg/L)

(Figure 1) and are a reflection of the low concentrations in local rainfall. Also,

the island’s sediments have provided little additional input.

The dominant metals in the surface waters are Fe and Al although both of these

metals have low concentrations, ranging from 0.19-2.85 mg/L (average. ≈ 1 mg/L)

for Al and 0.05-2.39 mg/L (average. ≈ 1 mg/L) for Fe.

SURFACE AND SHALLOW GROUNDWATERS

As previously suggested, the shallow groundwaters and surface waters of Bribie

Island are related physically and chemically due to infiltration and seepage. Both

are similar water types (Na,Mg-Cl) and both have similar concentrations of major

ions. Physico-chemical parameters such as pH, conductivity, and colour are also

very similar naturally.

Physical changes to the shallow groundwater regime, such as clearing of the

pines, will also affect surface waters. Clearing of the pine plantation since 1996

has resulted in a considerable rise in the perched shallow groundwater level.

Hydrographs of water levels indicate a rise of up to one meter in some areas since

clearing began. The increased water levels have a direct impact on surface water

distribution and permanency of wetlands. With the increased water levels more

low-lying ares have become waterlogged. In addition to this is the marked

seasonal distribution of surface water related to rainfall.

CONCLUSION

Surface waters on Bribie Island are of significance to the natural ecosystems on

the island itself and Pumicestone Passage due to their outflow into the passage.

Additionally, surface water on Bribie Island is of importance due to its

relationship with the perched shallow groundwater regime on the island. It is

therefore vital to understand the interaction between surface and groundwater on

this island.


ACKNOWLEGEMENTS

This project has been funded by the Natural Heritage Trust, DPI-Forestry, and

Caboolture Shire Council, while special thanks is given to DNR, National Parks,

HLA Envirosciences Pty. Ltd., and Pacific Harbour.

REFERENCES

Harbison, J. E. 1998. The Occurrence and Chemistry of Groundwater on Bribie Island, A large Barrier Island

in Moreton Bay, Southeast Queensland. Masters Thesis, QUT, Brisbane, QLD.

Harbison, J.E. and Cox, M.E. 1998. General features of the Occurrence of Groundwater on Bribie Island,

Moreton Bay. In: Tibbetts, I.R., Hall, N.J. and Dennison , W.C.eds. Moreton Bay and Catchment. pp.11-24

School of Marine Science, UQ, Brisbane.

Drever, J. I. 1997.The geochemistry of natural waters: Surface and Groundwater Environments. 3rd. Prentice

Hall, New Jersey.

Appendix B

The relationship between groundwater and surface water character and

wetland habitats, Bribie Island, Queensland (conference paper)

Presented: International Association of Hydrogeologists, Balancing the Groundwater

Budget Conference, Darwin 2002

Appendix B – IAH conference paper

THE RELATIONSHIP BETWEEN GROUNDWATER

AND SURFACE WATER CHARACTER AND

WETLAND HABITATS, BRIBIE ISLAND,

QUEENSLAND.

ARMSTRONG, T.J. AND COX, M.E.

Abstract

Bribie Island is a large barrier island in northern Moreton Bay, southeast

Queensland. The island is experiencing rapid urban and forestry development,

while use of the groundwater resource is unrestricted and unregulated. Here we

consider the hydrogeological regime of Bribie Island, and establish the

relationship groundwater has on surface water character and occurrence.

Establishing relationships between surface water and groundwater is essential

when considering land use impacts and changes as well as the island’s wetland

habitats. Examples of likely changes to the hydrological regimes on the island are

the current harvesting and re-planting of a commercial pine plantation which will

result in increased transpiration, the development of an abstraction bore field that

has the potential to affect water supply to the pine forest plus the potential to

encourage seawater encroachment, and the construction of a residential golf

course which may increase nutrient loads and affect environmental flow.

Preliminary results of groundwater elevations indicate that the surficial sands of

Bribie Island host an extensive perched water table commonly at a depth of 1

metre below the ground surface. Additionally, the water table indicates a rapid

response to rainfall as a result of highly permeable beach ridge sands.

Consequently, surface water runoff is limited. Most surface water expressions,

therefore, result from the shallow groundwater table intersecting the surface in

zones of low relief, particularly those of the Melaleuca dominated swales between

the sand ridges. Support for the close relationship between surface water and

shallow groundwater are their similarities in chemistry. For example, physico-

chemical parameters such as pH, Eh, and EC are all closely related. Additionally,


both waters have similar major dissolved ion concentrations and a high

concentration of dissolved organic material giving both surface water and shallow

groundwater a distinctive black colour, “black water”.

Key Words groundwater/surface water interactions, coastal aquifers,

recharge, unconsolidated sediments, island hydrogeology, Queensland, Australia.

INTRODUCTION

The coastal environment of southeast Queensland, and particularly the area of

Moreton Bay, hosts a diverse range of environmental settings such as marine,

estuarine, freshwater, streams/rivers, and islands. Moreton Island and North

Stradbroke Island form the outer barrier for Moreton Bay and are composed of

megadune systems with profiles extending 200 meters above sea level. Bribie

Island lies in northern Moreton Bay approximately 65 km north of Brisbane.

Bribie is a large low-lying barrier sand island separated from the mainland by the

shallow estuarine wetlands of Pumicestone Passage (Fig 1). Unlike the massive

sand masses of the two outer islands, Bribie Island is significantly smaller in

terms of size and water resources.

Figure 1. Moreton Bay showing the main

sand islands and the location of the study


Over the past few decades the entire Pumicestone Passage catchment, including

Bribie Island, has experienced rapid growth in terms of urbanisation and

agriculture. Urban development is restricted to the southern extent of Bribie

Island, while pine plantations and National Park occupy the northern two-thirds of

the island. Development such as forestry plantations and residential estates has

been in question due to the recent degradation of water quality of some parts of

Pumicestone Passage and surrounding area. As development continues to occur

on Bribie Island, the finite water resources of the island and wetland habitats,

largely fed by groundwater could be degraded. It is, therefore, necessary to

understand the hydrological regimes of the island for effective land and water

management.

In an environment such as Bribie Island, quite complex relationships exist

between groundwater and surface water. As with many sand islands, an

unconfined shallow groundwater table exists over an extensive area of the island.

The shallow groundwater table is in direct contact with surface water and the

interaction between the two is considered important in terms of both physical

processes and chemical properties. This study aims to identify the main

hydrogeological controls and processes that effect groundwater on Bribie Island,

and summarise how these factors affect surface water character and related

habitats.

PHYSICAL SETTING

Bribie Island experiences a sub-tropical climate with mean daily temperatures

between 15 - 29 oC in summer, and 9-20 oC in winter. The island receives rainfall

throughout the year, however there is a distinctly wetter period through the

summer months (December - March), including the occurrence of infrequent

cyclones. Pan evaporation at Brisbane Airport is approximately 1570 mm per

year. The island has very low relief with a mean elevation of 5 m and a maximum

elevation of 17 m above sea level. As a consequence of the low relief of the

island combined with the high permeability of the sand formation, surface

drainage is poor resulting in large swampy areas that are inundated during the

wetter months.


The surface topography of the island is dominated by two large accretionary

beach ridge systems that are aligned to the present shoreline and extend through

the long axis of the island. A major swale (interconnected low-lying Melaleuca

swamps) separate the two beach ridge systems and is the dominant drainage

feature of the island (Fig 2). In the far north, Bribie Island tapers towards the

northern entrance of Pumicestone Passage as a narrow sand spit. The western side

of the island is dominated by low-lying marine clayey sands that have been

incised by Pumicestone Passage. Southern Bribie Island consists of younger

Figure 2. Bribie Island locality map showing piezometer network, and transect A-A’ for figure 3.


accretionary beach ridges. The eastern foredunes occur as a narrow strip along

the eastern coast. These dunes are approximately 10 m high and protect coastal

lagoons situated immediately behind them.

There are four coastal lagoons along the eastern shoreline and three tidal creeks on

the western shoreline. Furthermore, two large tidal canal networks have been

excavated along the south-western shore to drain the extensive urban development

in the area. In the north of the island is a single creek system, Westaways Creek

that drains the central swale (Fig. 2).

The exotic slash pine (Pinus Elliottii) has replaced large tracts of native vegetation

in the northern two-thirds of the island but is generally restricted to the two major

beach ridge systems. The water logged low-lying interdune depressions are

dominated by native remnant Melaleuca. The pine plantation has experienced

considerable difficulties during its first rotation such as fire, water logging and

insect attack. The plantation has undergone harvesting since 1996 and will cease

at the end of 2001. Queensland Parks and Wildlife (QPW) has recently acquired

the northern two-thirds of Bribie Island including the pine plantation from private

ownership. QPW has subsequently granted special lease to the Queensland

Department of Primary Industries - Forestry, to continue reduced forestry

operations and commence with planting the second rotation of trees.

The areas not used as pine plantations still exist in their natural state and are

preserved as National Parks. The major areas are along the coastal strip. The

vegetation types of Bribie Island reflect local sediment type and soil

water/shallow groundwater occurrence. The beach ridges are dominated by

Banksia robur, while Melaleuca, as previously stated, dominates the interdune

depressions. Red Gum (Eucalyptus tereticornis) and Swamp box (Lophostemon

suaveolens) dominate the western section of the island and parts of the central

swale. Acacia, Callitris, and Eucalyptus dominate the southern younger beach

ridge sediments. Small patches of sedgeland also exist and are dominated by

Gahnia seiberana, Lepironia articulata and Restio pallens (Coaldrake, 1961).


METHODS

The hydrology of Bribie Island is currently being investigated by ongoing

monitoring of a comprehensive groundwater bore network and a selection of

surface water sites throughout the island. The groundwater monitoring program is

focused on a west – east transect of bores central to the island initially established

by the Queensland Department of Natural Resources and Mines (DNMR). An

additional drilling program in March 2001 by Queensland University of

Technology (QUT) added sixteen new piezometers to the transect. This reference

transect is now comprised of twenty-three piezometers and has provided a highly

detailed cross-section through the wide section of the island enabling stratigraphic

correlations to be better defined and hydraulic gradients measured (Fig. 3). The

main objectives of the drilling were to: 1) better define the shallow perched water

table gradients across the island, 2) enable water samples to be collected from

various stratigraphic heights throughout the profile of the island, 3) allow better

definition of the coffee rock layer, and 4) constrain the character of the underlying

sandstone bedrock. Analysis of drilling returns from this program and evaluation

Figure 3. East-west transect of Bribie Island, A-A’. The unconfined water table is shown as

in blue. The potentiometric water level is shown in red.


of previous drilling programs confirms that the stratigraphy of the island results in

distinct heterogeneity of aquifer material.

Monitoring of all piezometers for water levels has occurred on a monthly basis

since August 2000. This monitoring program has been designed to record

seasonal changes in hydraulic gradients across the island and provide hydrological

evidence to confirm a two layered aquifer conceptual model of shallow

unconfined groundwater body perched above partially confined groundwater.

The piezometers have also made possible the monitoring of groundwater for the

physico-chemical parameters pH, Eh, electrical conductivity (EC), temperature

and dissolved oxygen (DO). Field measurements of the parameters have been

monitored at an interval of every two to three months. Thirty-one surface water

expressions across the island have also been seasonally monitored for physico-

chemical parameters. Water samples have been collected from both groundwater

and surface waters at three to four month intervals. These samples have been

analytically analysed for major and minor ions as well as dissolved organic

carbon.

GEOLOGICAL FRAMEWORK

The combination of previous drilling programs and the more recent Queensland

University of Technology (QUT) drilling program has enabled a detailed

investigation of the geologic framework of the island. The complex form of the

island is a result of sea level variations during the Late Pleistocene and Holocene.

The island is composed of Quaternary sand deposits, overlying bedrock of Lower

Jurassic sandstone (Fig 3).

This arkosic sandstone is light grey in colour, medium to coarse grained, with

some shale bands and thin conglomerate lenses (Ishaq, 1980). There are no

outcrops of sandstone on Bribie Island. The weathered profile of the sandstone

can vary in thickness from several meters to 20 m thick on the adjacent mainland

(Ezzy et al., 2000). The weathered profile exhibits laterite zonation. At the base

of the weathered profile exists saprolite which then grades upward into a more


extensively weathered mottled silty clay. Capping the weathered profile is the

most extensively weathered and leached unit represented by a ferricrete crust.

Overlying the weathered sandstone is a sequence of clayey sands that have been

deposited in low energy bay and lagoonal environments (Hekel and Day, 1976;

Ishaq, 1980). The kaolinite rich clays are generally grey to white to green in

colour and contain thin lenses of fine gravel and fine sands (Harbison and Cox,

1998).

The surficial sediments of Bribie Island consist of Holocene to Pleistocene beach

sands. The Pleistocene accretion ridges and swales formed from deposition of

beach sands by eustatic oscillations (Lumsden, 1964; Coaldrake, 1960) during

periods of beach ridge propagation. The Pleistocene sands constitute the most

widespread unit within the island and consist of fine to medium quartz sand. The

ridges longitudinal axis are aligned parallel with the prevailing southeast winds

(Harbison and Cox, 1998). The total thickness of the Pleistocene sediments vary

from 5 to 25 m, and dip gently to the south and east beneath the Holocene beach

ridge sediments (Ishaq, 1980).

Contained within the Pleistocene sediments is an extensive podsol horizon at an

approximate depth of 5-6 m with a maximum measured thickness of 9 m. This

layer of dark coloured indurated sand is referred to locally as “coffee rock”. It has

been described as quartz sand grains cemented by the in-filling of pores by a

variety of cements, predominately organic matter and clays (Farmer et al., 1983

and Thompson et al., 1996). Considerable amounts of Fe and Al are also

associated with coffee rock formation (Farmer, 1983). Due to the reduced

porosity and permeability of the sand profile, coffee rock plays an important role

in hydrological processes across Bribie Island; of note is the perching of shallow

unconfined groundwater.


HYDROGEOLOGY

Groundwater occurrence

The heterogeneous material forming the sand mass of the island produces distinct

water bodies that have differing characters and are controlled by a variety of

processes. The groundwater resource can be divided into two water bodies,

shallow perched unconfined groundwater and deep (basal) partially confined

groundwater. These bodies have differing hydrological processes, physico-

chemical properties and water composition. The deep partially confined

groundwater occurs underneath the leaky confining coffee rock horizon contained

within the Pleistocene beach ridge sands. Monitoring of the extensive network of

piezometers on the island has indicated that the potentiometric surface of the

partially confined basal aquifer has an approximate maximum height of 3 m above

Figure 4. Water levels of the east west transect on 10 April, 2001.


the Australian Height Datum (AHD). The potentiometric surface mound is

therefore very slight and typically occurs toward the centre of the island.

Across the island the unconfined water table contour generally follows local

topography forming two distinct groundwater mounds within the two main beach

ridge systems. The water table is commonly at 1 m depth while it has an

approximate maximum elevation of 6 m AHD. Contouring of both the

unconfined water table and the potentiometric surface results in a clearly defined

view of the two systems (Fig. 4).

Groundwater – surface water interaction

With the unconfined water table being in such close proximity to the ground

surface, interdune depressions, drains and fire-fighting trenches are often

discharge points for environmental flow from the beach ridge systems.

Widespread areas of the island are covered by naturally low-lying depressions

ranging in size from metres to tens of metres in diameter. These local low points

occur as minor swales forming between minor ridges that are contained within the

larger beach ridge system. The other major source of surface water on the island

is contained within fire-fighting trenches. These excavations result in some sites

to be permanently connected and acting as a window to the shallow unconfined

water table. Most of these excavations have been strategically placed to drain

particular areas and hence, some drainage patterns of the area have been altered.

Additionally, there are a series of large coastal lagoons that occur along the

eastern coast behind the beach foredunes. These form from the mixing of fresh

groundwater discharge and over dune wash from large tides and storm surges.

Another occurrence of surface water on the island results from organic silts and

clays being transported into the low-lying areas where, upon settling, create a type

of seal that reduces the infiltration rate of the surface water after rainfall (Harbison

and Cox, 1998). For this reason surface water can remain in these lows for

extended periods after a significant rainfall event before the water either

evaporates or infiltrates.


The drainage system on Bribie Island is not well developed. The most significant

surface water flow is from the two major beach ridge systems into the major

central swale. In general, the central swale has a slow northerly flow discharging

into Pumicestone Passage via Westerways Creek in the north of the island. The

southern section of the central swale flows south and discharges into the passage

via Wright’s Creek. This southerly flow is attributed to topographic changes,

however, the southern causeway across the central swale may have caused a

reduction of flow to the north. Evapotranspiration on Bribie Island is another

substantial loss of unconfined groundwater. Field observations and hydrographs

indicate that pine plantation growth and harvest have a substantial effect on

unconfined groundwater levels across the island, influencing discharge volume to

wetland areas.

HYDROCHEMISTY

Ionic chemistry

The similarities in ionic chemistry of both unconfined groundwater and surface

water suggest that groundwater-surface water interactions exist. Both surface

Figure 5. Piper diagram of major ion chemistry

for surface water and groundwater. Arrow


water and unconfined groundwater typically are Na-Cl or Na, Mg-Cl water types

(Fig. 5); they have chemical ratios similar to local rainfall indicating this as the

primary recharge source. The enrichment of Ca is attributed to carbonate lenses

(remnant shell material) scattered throughout the beach ridge sediments. Due to

the low pH of both surface water and unconfined groundwater, HCO3

concentrations have been drastically reduced. Bicarbonate enrichment increases

with depth and is restricted to the partially confined groundwater underlying the

coffee rock horizon (Armstrong, 2000).

The partially confined groundwater is depleted in sulfate as a result of sulfur

reduction and loss of H2S. The reducing environments of the unconfined aquifer

and wetland areas promote the enrichment of sulfate.

The dominant minor elements in unconfined groundwater and surface water are

Fe and Al, both of which have low concentrations. This may be attributed to the

complexing of Fe and Al by organic acidic solutes, which results in leaching them

from the upper horizons and depositing them in deeper layers. This process is

documented in the formation of coffee rock (Thompson et al., 1996) and indicates

a poorly buffered unsaturated zone.

Physico-Chemical Properties

Physico-chemical averages of groundwater and surface water samples collected

through the sampling period of August 2000 – October 2001 further characterise

the different water bodies on Bribie Island (Table. 1). The majority of

groundwater and surface water on Bribie Island is fresh, with the exceptions of

coastal lagoons, tidal creeks, and tidally influenced groundwater. A notable

difference between the water bodies is the value of pH. The pH of partially

confined groundwater is approximately three units more alkaline than either

unconfined groundwater or surface water. The acidic pH values of the unconfined

groundwater and surface water result from the decomposition of organic matter.

Fallen leaf litter decomposes to produce organic acids and dissolved organic

carbon.


Table 1. Average physico-chemical parameters for groundwater and surface water of Bribie Island

for August 2000 – October 2001.

Sample DO

ppm

EC

µS/cm

Eh

mV

pH T oC

Partially confined

groundwater

0.7 335 216 6.2 22.2

Unconfined groundwater 2.8 203 279 3.9 20

Wetlands 4.8 220 413 3.5 23

Excavations 3.2 270 364 3.5 23

Coastal lagoons 7.8 44 000 383 7.0 25.3

Rainfall events flush the organic acids and dissolved organic carbon into the

islands wetlands, where the substances percolate down to the unconfined water

table. A dark colouring to the unconfined groundwater and surface water is

attributed to the high concentrations of dissolved organic carbon. The dark brown

to black colouring of this low pH water is often referred to as “black water”, and

is common to many low-lying poorly drained coastal settings.

FUTURE DEVELOPMENT IMPLICATIONS

The interrelationships between the physical settings and the hydrological

processes of Bribie Island are of great significance in the management of the

island habitats. Harvesting of the first rotation of pines will be complete in 2002.

A significant reduction in the evapotranspiration rate has occurred since the

removal of the pines. Hydrographs indicate a considerable rise in the unconfined

water table has resulted from this reduction in evapotranspiration. The increased

height of the unconfined water table has directly impacted on surface water

distribution by creating new and extending the existing water logged areas. The

permanency of these wetland areas has also increased as a consequence of the

greater volume of groundwater discharge into these areas.

Initial re-planting of the plantation started in 2001. Regrowth of the pines should

reverse some of the harvesting affects on the hydrological regime of the island.

Once the new plantation is established evapotranspiration rates should return to

pre-harvest levels. The increased rate of evapotranspiration may lead to a decline

in the water table level, which should decrease the amount of groundwater


discharge to the low-lying areas. Some wetlands will completely dry out while

others will only reduce in size. However, these relationships still need to be

quantified.

Previous groundwater modelling of the island has overlooked aquifer

heterogeneities such as the coffee rock horizon. Coffee rock has a reduced

porosity and permeability that affects groundwater storage and movement (Fig. 3).

Harbison and Cox (1998) estimated the volume of coffee rock to be 7.8 x 108 m3

or approximately 37 % of the aquifer volume. Therefore, disregarding such a

significant component of the hydrological regime results in an over estimate of the

water resource. Recent modelling indicates that for a 10 ML/day extraction rate,

water levels surrounding the bore field may fall to under 1 m AHD. As suggested

by Ishaq (1980) withdrawal of water from the bore field is likely to lower the

water table beneath part of the pine plantation, which could affect the growth of

pine trees. Additionally, if over pumping occurs and hydraulic gradients are

reversed groundwater discharge to wetland habitats and surface water runoff may

be greatly reduced while seawater intrusion may also occur.

The construction of a new residential golf course in the southwest corner of the

existing pine plantation adjoining the Pacific Harbour canal residential estate will

commence in the first half of 2002. Fertilizers and pesticides applied to a golf

course need to be considered. The potential for nitrate (NO3-), ammonium (NH4

+),

and phosphate (PO43-) to enter the unconfined groundwater and surface water

must be defined.

CONCLUSION

This study illustrates the close relationship between the perched unconfined

groundwater and much of the wetland areas of Bribie Island. These relationships

exist both physically and chemically. A detailed transect shows that the

topography across the island effects the hydraulic gradients of the unconfined

water table which directs environmental flow into low-lying areas. Groundwater

discharge into these low-lying areas results in water logged conditions for many

parts of the island. These water logged areas are an important environmental


setting as they support wetland habitats. The wetlands and shallow groundwater

are typically dark brown – black coloured with low pH values and water types of

Na-Cl and Na, Mg-Cl. Hydrochemistry through the profile of the island displays

different groundwater composition with depth. Water composition highlights the

relationship between surface water, the unconfined groundwater and the evolution

of these waters into the basal partially confined aquifer. Aquifer heterogeneities

such as the leaky confining unit (the coffee rock horizon) dominate the

hydrological processes of the island and should be considered when assessing the

environmental setting and the water resources of Bribie Island.

ACKNOWLEDGEMENTS

The authors are grateful for funding support by the Natural Heritage Trust

program, Caboolture Shire Council, and Queensland Department of Primary

Industries – Forestry. Assistance by staff of the Department of Natural Resources

and Mines (Peter Cochrane and Robert Ellis), Department of Primary Industries –

Forestry (Stan Ward and Dr. Ken Bubb), Queensland Parks and Wildlife, Pacific

Harbour (Greg Smith and Warren Russell), and HLA Envirosciences Pty. Ltd.

(Peter Scott) in providing data, expertise, and field equipment is greatly

appreciated. Thanks are extended to Dr. Micaela Preda of the Queensland

University of Technology for helpful reviews and discussion.

REFERENCES

Armstrong T (2000) Chemical character of surface waters on Bribie Island: a preliminary assessment. In: Cox

ME (ed) proc PASSCON 2000, Pumicestone Passage & Deception Bay Catchment Conference, 22-23

November, pp 77-79

Coaldrake JE (1960) Quaternary history of the coastal lowlands of southern Queensland. Journal of the

Geological Society of Australia 7:403-408

Coaldrake JE (1961) The ecosystem of the coastal lowlands (“wallum”) of southern Queensland.

CSIRO Bulletin No. 283, Melbourne Ezzy T, Cox ME, Brooke B (2000) The geological setting and its control over groundwater within the

Meldale coastal plain. In: Cox ME (ed) proc PASSCON 2000, Pumicestone Passage & Deception Bay

Catchment Conference, 22-23 November, pp 23-25

Farmer VC, Skjemstad JO, Thompson CH (1983) Genesis of humus B horizons in hydromorphic humus

podzols. Nature 304/5924: 342-344.


Harbison JE, Cox ME (1998) General features of the occurrence of groundwater on Bribie Island, Moreton

Bay. In: Tibbitts IR, Hall NJ, Dennison WC (ed) Moreton Bay and Catchment. School of Marine Science,

The University of Queensland, Brisbane 11-24

Hekel H, Day RW (1976) Quaternary geology of the Sunshine Coast, southeast Queensland. Geological

Survey of Queensland Record 1979/16, Brisbane

Ishaq S (1980) Bribie Island water supply – hydrogeological reconnaissance of the southern part of Bribie

Island. Geological Survey of Queensland Record 1980/44, Brisbane

Lumsden AC (1964) Bribie Island water supply. Geological Survey of Queensland Record, 1964/8, Brisbane

Thompson CH, Bridges EM, Jenkins DA (1996) Pans of humic podzols (Humods and Aquods) in coastal

southern Queensland. Australian Journal of Soil Research 34:161-182

Appendix C

Controls over aquifer heterogeneity within a large sand island and analysis by

hydraulic testing, Bribie Island, Queensland, Australia (accepted

manuscript - Hydrogeology Journal)

halla

This article is not available online. Please consult the hardcopy thesis available from the QUT Library

Appendices

Section B: Data

Appendix D Stratigraphic Logs

Appendix D – Stratigraphic logs

Appendix E

Sediment Age Dating

halla

This article is not available online. Please consult the hardcopy thesis available from the QUT Library

Appendix F

Groundwater Level Data

Gro

undw

ater

Lev

el (m

) W

ell N

o.

Gro

und

leve

l (m

) 13

/12/

00

15/2

/01

1/5/

01

22/5

/01

4/7/

01

1/8/

01

19/9

/01

12/1

0/01

19

/10/

01

13/1

1/01

TO

C

-2

.02

-1.4

0

-1.3

4 -1

.88

-1.9

0 -2

.10

-2.1

6 -2

.17

M

W1

AH

D

7.80

5.

777

6.39

7

6.45

7 5.

917

5.89

7 5.

697

5.63

7 5.

627

TO

C

-2

.03

-1.1

7

-1.2

4 -1

.59

-1.5

8 -2

.11

-2.2

7 -2

.28

-2.1

3 M

W2

AH

D

7.36

5.

328

6.18

8

6.11

8 5.

768

5.77

8 5.

248

5.08

8 5.

078

5.22

8 TO

C

-1

.88

-0.8

1 -1

.00

-1.1

0 -1

.39

-1.3

6 -1

.78

-1.8

8 -1

.79

-1.5

9 M

W3

(S)

AH

D

6.93

5.

054

6.12

4 5.

934

5.83

4 5.

544

5.57

4 5.

154

5.05

4 5.

144

5.34

4 TO

C

-5

.34

-5.1

9 -5

.28

-5.3

9

M

W3

(D)

AH

D

7.05

1.

71

1.86

1.

77

1.66

TO

C

-4

.31

-2.8

6

-2.3

6 -2

.51

-2.4

6 -2

.63

-2.6

7 -2

.66

-2.5

1 M

W4

(S)

AH

D

5.50

1.

19

2.64

3.14

2.

99

3.04

2.

87

2.83

2.

84

2.99

TO

C

-5

.15

-4.6

7

-4.8

4 -4

.96

-4.9

2 -5

.24

-5.2

5 -5

.18

-5.1

7 M

W4

(D)

AH

D

5.81

0.

65

1.14

0.97

0.

85

0.89

0.

57

0.56

0.

63

0.64

TO

C

-2

.17

-1.5

7

-1.8

5 -2

.02

-1.9

5 -2

.19

-2.2

6 -2

.24

-1.9

7 M

W5

(S)

AH

D

5.54

3.

37

3.97

3.69

3.

52

3.59

3.

35

3.28

3.

30

3.57

TO

C

-4

.69

-4.1

8

-4.3

3 -4

.46

-4.4

4 -4

.81

-4.8

6 -4

.82

-4.8

2 M

W5

(D)

AH

D

5.62

0.

93

1.44

1.29

1.

16

1.18

0.

81

0.76

0.

80

0.80

TO

C

-1

.04

-0.6

1

-0.6

8 -0

.85

-0.7

7 -1

.06

-1.0

8 -0

.96

-0.7

1 M

W6

(S)

AH

D

7.07

6.

03

6.46

6.39

6.

22

6.30

6.

01

5.99

6.

11

6.36

TO

C

-5

.60

-5.3

6

-5.4

7 -5

.60

-5.6

5 -5

.86

-5.8

6 -5

.83

-5.9

3 M

W6

(D)

AH

D

6.91

1.

31

1.55

1.44

1.

31

1.26

1.

05

1.05

1.

08

0.98

TO

C

-1

.22

-0.4

8

M

W7

(S)

AH

D

7.31

6.

09

6.83

TO

C

-5

.73

-5.5

0

-5

.78

-5.7

9 -5

.91

-5.8

9 -5

.83

-5.9

0 M

W7

(D)

AH

D

7.15

1.

42

1.65

1.

37

1.36

1.

24

1.26

1.

32

1.25

TO

C

-2

.02

-1.4

8 -1

.62

-1.6

6 -1

.85

-1.7

7 -2

.08

-2.1

2 -2

.09

-1.8

4 M

W8

(S)

AH

D

8.09

6.

07

6.61

6.

47

6.43

6.

24

6.32

6.

01

5.97

6.

00

6.25

TO

C

-6

.13

-5.9

9 -6

.06

-6

.30

-6.3

6 -6

.45

-6.3

9 -6

.36

-6.4

6 M

W8

(D)

AH

D

8.31

2.

18

2.32

2.

25

2.

01

1.95

1.

86

1.92

1.

95

1.85

Appendix F – groundwater level data

Gro

undw

ater

Lev

el (m

) W

ell N

o.

Gro

und

leve

l (m

) 21

/12/

01

10/1

/02

15/2

/02

22/3

/02

18/4

/02

25/7

/02

TOC

-2

.10

-1.7

7 -1

.66

MW

1 A

HD

7.

80

5.

697

6.02

5 6.

137

TOC

-2.2

8

MW

2 A

HD

7.

36

5.07

8

TOC

-1.8

0

-1

.99

-1.6

0 -1

.23

MW

3 (S

) A

HD

6.

93

5.13

4

4.

944

5.33

1 5.

704

TOC

MW

3 (D

) A

HD

7.

05

TOC

-2.5

6 -2

.50

-2.6

5 -2

.64

-2.4

7 -2

.32

MW

4 (S

) A

HD

5.

50

2.94

3.

00

2.85

2.

86

3.03

3.

18

TOC

-5.1

9 -5

.15

-5.3

6 -5

.46

-5.2

3 -5

.10

MW

4 (D

) A

HD

5.

81

0.61

0.

65

0.45

0.

35

0.58

0.

71

TOC

-2.0

3 -2

.00

-2.1

2 -2

.01

-1.8

2 -1

.79

MW

5 (S

) A

HD

5.

54

3.51

3.

54

3.42

3.

53

3.72

3.

75

TOC

-4.7

6 -4

.77

-5.0

7 -5

.19

-4.9

3 -4

.72

MW

5 (D

) A

HD

5.

62

0.86

0.

85

0.55

0.

43

0.69

0.

90

TOC

-0.9

1 -0

.87

-1.0

5 -1

.06

-0.8

3 -0

.89

MW

6 (S

) A

HD

7.

07

6.16

6.

20

6.02

6.

01

6.24

6.

18

TOC

-5.7

5 -5

.80

-6.0

2 -6

.14

-5.9

8 -5

.78

MW

6 (D

) A

HD

6.

91

1.16

1.

11

0.89

0.

77

0.94

1.

13

TOC

MW

7 (S

) A

HD

7.

31

TOC

-5.9

1 -5

.90

-6.0

1 -6

.05

-5.9

1

MW

7 (D

) A

HD

7.

15

1.24

1.

25

1.14

1.

10

1.24

TOC

-1.9

2 -1

.87

-2.1

3 -2

.19

-1.9

4 -1

.76

MW

8 (S

) A

HD

8.

09

6.17

6.

22

5.97

5.

91

6.15

6.

33

TOC

-6.3

3 -6

.39

-6.5

4 -6

.64

-6.4

9 -6

.30

MW

8 (D

) A

HD

8.

31

1.98

1.

92

1.77

1.

68

1.82

2.

01


Gro

undw

ater

Lev

el (m

) W

ell N

o.

Gro

und

leve

l (m

) 22

/8/0

0 4/

9/00

10

/10/

00

7/11

/00

13/1

2/00

15

/2/0

1 6/

3/01

10

/4/0

1 1/

5/01

22

/5/0

1 6/

6/01

TO

C

-1

.90

-1

.77

-1.9

0 00

84

AH

D

3.37

1.47

1.60

1.

47

TOC

-0.6

9

-0.6

2 -0

.68

-0

.68

0085

A

HD

2.

77

2.

08

2.

15

2.09

2.09

TO

C

00

86

AH

D

3.94

TOC

-6

.37

-6.4

0 -6

.53

-6.4

6 -6

.56

-6.5

1 -6

.54

-6.4

2 -6

.44

-6.4

8 -6

.51

0088

A

HD

8.

86

2.49

2.

46

2.34

2.

40

2.30

2.

35

2.32

2.

44

2.42

2.

38

2.35

TO

C

-3.7

1 -3

.77

-3.9

0 -3

.85

-4.0

6 -3

.65

-3.6

7 -3

.82

-3.9

1 -3

.98

-4.0

3 00

89

AH

D

6.02

2.

31

2.25

2.

12

2.17

1.

96

2.37

2.

35

2.20

2.

11

2.04

1.

99

TOC

-3

.26

-3.2

9 -3

.33

-3.3

1 -3

.56

-3.2

5 -3

.27

-3.3

9 -3

.44

-3.5

7 -3

.65

0100

A

HD

6.

06

2.80

2.

77

2.73

2.

75

2.50

2.

81

2.79

2.

67

2.62

2.

49

2.41

TO

C

-6.3

3 -6

.40

-6.4

9 -6

.41

-6.5

2 -6

.40

-6.4

3 -6

.31

-6.3

3 -6

.44

-6.5

1 01

01

AH

D

8.83

2.

50

2.43

2.

34

2.42

2.

31

2.43

2.

40

2.52

2.

50

2.39

2.

32

TOC

-1

.48

-1.1

9 -1

.59

-1.0

2 -1

.06

-1.0

3 -1

.13

-1.1

0 -1

.17

0114

A

HD

5.

67

4.20

4.

48

4.08

4.

65

4.61

4.

64

4.54

4.

57

4.50

TO

C

-1.1

0 -1

.20

-1.4

4 -1

.21

-1.4

8 -0

.84

-0.8

6 -0

.92

-1.0

7 -1

.06

-1.1

7 01

15

AH

D

6.96

5.

86

5.76

5.

52

5.75

5.

48

6.12

6.

10

6.04

5.

89

5.90

5.

79

TOC

-8

.89

-8.9

6 -9

.15

-9.1

2

-9.1

1

-9

.10

0120

A

HD

10

.87

1.98

1.

91

1.72

1.

75

1.

76

1.77

TO

C

-3.9

9 -3

.79

-3.6

8 01

23

AH

D

6.84

2.

85

3.05

3.

16

TOC

-3

.13

-3.1

9 -3

.37

-3.1

8 -3

.33

-2.8

0 -2

.83

-2.9

3 -3

.04

-3.1

3 -3

.21

0126

A

HD

6.

81

3.68

3.

62

3.44

3.

63

3.48

4.

01

3.98

3.

88

3.77

3.

68

3.60

TO

C

-1.1

0

-1

.38

-1.5

2 01

29

AH

D

3.49

2.

39

2.11

1.

97

TOC

0121

A

HD

9.

89


Gro

undw

ater

Lev

el (m

) W

ell N

o.

Gro

und

leve

l (m

) 15

/6/0

1 5/

7/01

1/

8/01

19

/9/0

1 12

/10/

01

19/1

0/01

13

/11/

01

21/1

2/01

10

/1/0

2 15

/2/0

2 22

/3/0

2 TO

C

-2

.06

-2.0

6 -2

.42

-2.4

8 -2

.48

-2.3

7

-2.8

0 00

84

AH

D

3.37

1.31

1.

31

0.95

0.

89

0.89

1.

00

0.

57

TOC

-0

.73

-1.0

8 -1

.12

-1.0

4 -0

.65

-1

.64

0085

A

HD

2.

77

2.04

1.

69

1.65

1.

73

2.12

1.13

TO

C

-3.0

4

-3.3

3 00

86

AH

D

3.94

0.

90

0.

61

TOC

-6

.53

-6.6

0 -6

.64

-6.7

9 -6

.83

-6.8

2 -6

.81

-6.7

8 -6

.78

-6.9

2 -7

.01

0088

A

HD

8.

86

2.33

2.

26

2.22

2.

07

2.03

2.

04

2.05

2.

08

2.08

1.

95

1.85

TO

C

-4.0

7 -4

.14

-4.1

5 -4

.27

-4.2

9 -4

.27

-4.2

1 -4

.10

-4.0

9 -4

.28

-4.3

0 00

89

AH

D

6.02

1.

95

1.88

1.

87

1.75

1.

73

1.75

1.

81

1.92

1.

93

1.74

1.

72

TOC

-3

.66

-3.7

4 -3

.74

-3.8

4 -3

.82

-3.7

6 -3

.74

-3.6

0 -3

.63

-3.8

4 -3

.92

0100

A

HD

6.

06

2.40

2.

32

2.32

2.

22

2.24

2.

30

2.32

2.

46

2.43

2.

22

2.14

TO

C

-6.4

9 -6

.59

-6.6

2 -6

.81

-6.8

2 -6

.73

-6.8

4 -6

.64

-6.7

0 -6

.94

-7.1

0 01

01

AH

D

8.83

2.

34

2.24

2.

21

2.02

2.

01

2.10

1.

99

2.19

2.

13

1.90

1.

73

TOC

-1.2

7 -1

.25

-1.4

7 -1

.44

-1.3

2 -1

.18

-1

.42

-1

.77

0114

A

HD

5.

67

4.

40

4.42

4.

20

4.23

4.

35

4.49

4.25

3.90

TO

C

-1

.30

-1.2

7 -1

.50

-1.5

4 -1

.42

-1.2

1 -1

.35

-1.3

4 -1

.62

-1.7

4 01

15

AH

D

6.96

5.66

5.

69

5.46

5.

42

5.54

5.

75

5.61

5.

62

5.34

5.

22

TOC

-9.1

3 -9

.16

-9.2

6 -9

.28

-9.2

6 -9

.33

-9.6

9

0120

A

HD

10

.87

1.

74

1.71

1.

61

1.59

1.

61

1.54

1.

18

TO

C

-3

.77

-3.7

5 -4

.09

-4.1

0 -4

.09

-3.9

5 -4

.36

01

23

AH

D

6.84

3.07

3.

09

2.75

2.

74

2.75

2.

89

2.48

TOC

-3

.25

-3.3

4 -3

.32

-3.5

3 -3

.60

-3.6

1 -3

.46

-3.5

0 -3

.36

-3.6

3 -3

.69

0126

A

HD

6.

81

3.56

3.

47

3.49

3.

28

3.21

3.

20

3.35

3.

31

3.45

3.

18

3.12

TO

C

-1.5

3 -1

.58

-1.5

3 -1

.83

-1.9

3 -1

.91

-1.7

9 -1

.95

-1.8

9 -2

.20

-2.3

9 01

29

AH

D

3.49

1.

96

1.91

1.

96

1.66

1.

56

1.58

1.

70

1.54

1.

60

1.29

1.

10

TOC

-8

.16

-8.4

3 -8

.40

-8.3

9 -8

.30

-8

.82

0121

A

HD

9.

89

1.73

1.

46

1.49

1.

50

1.59

1.07


Gro

undw

ater

Lev

el (m

) W

ell N

o.

Gro

und

leve

l (m

) 18

/4/0

2 25

/7/0

2 TO

C

-2.7

9 -2

.68

0084

A

HD

3.

37

0.58

0.

69

TOC

-0

.93

-1.2

1 00

85

AH

D

2.77

1.

85

1.56

TO

C

-3.2

3 -3

.15

0086

A

HD

3.

94

0.71

0.

79

TOC

-6

.96

-6.7

8 00

88

AH

D

8.86

1.

90

2.08

TO

C

-4.4

3 -3

.89

0089

A

HD

6.

02

1.59

2.

13

TOC

-3

.70

-3.5

3 01

00

AH

D

6.06

2.

36

2.53

TO

C

-6.9

3 -6

.77

0101

A

HD

8.

83

1.90

2.

06

TOC

-1

.47

-1.3

2 01

14

AH

D

5.67

4.

20

4.35

TO

C

-1.4

7 -1

.31

0115

A

HD

6.

96

5.49

5.

65

TOC

-9

.53

-9.4

6 01

20

AH

D

10.8

7 1.

35

1.41

TO

C

-4.1

2

0123

A

HD

6.

84

2.72

TOC

-3

.48

-3.5

3 01

26

AH

D

6.81

3.

33

3.28

TO

C

-2.2

5 -2

.29

0129

A

HD

3.

49

1.24

1.

20

TOC

-8

.56

-8.5

8 01

21

AH

D

9.89

1.

33

1.31


Gro

undw

ater

Lev

el (m

) W

ell N

o.

Gro

und

leve

l (m

) 10

/4/0

1 1/

5/01

22

/5/0

1 5/

6/01

15

/6/0

1 3/

7/01

1/

8/01

19

/9/0

1 12

/10/

01

19/1

0/01

13

/11/

01

TOC

-1

.13

-1.2

6 -1

.32

-1.3

9

-1.5

2 -1

.47

-1.7

3 -1

.79

-1.7

5 -1

.53

0131

A

HD

6.

73

5.60

5.

47

5.41

5.

34

5.

21

5.26

5.

00

4.94

4.

98

5.20

TO

C

-0.9

1 -1

.05

-1.0

3 -1

.10

-1

.20

-1.1

5 -1

.48

-1.5

4 -1

.41

-1.1

9 01

32

AH

D

6.18

5.

27

5.13

5.

15

5.08

4.98

5.

03

4.70

4.

64

4.77

4.

99

TOC

-2

.21

-2.4

7 -2

.45

-2.9

5

-3.0

3 -2

.96

-3.0

8 -3

.17

-3.0

9 -3

.07

0133

A

HD

5.

71

3.50

3.

24

3.26

2.

76

2.

68

2.75

2.

63

2.54

2.

62

2.64

TO

C

-1.0

8 -1

.25

-1.2

3 -1

.32

-1

.45

-1.3

5 -1

.62

-1.6

8 -1

.56

-1.3

5 01

34

AH

D

4.73

3.

65

3.48

3.

50

3.41

3.28

3.

38

3.11

3.

05

3.17

3.

38

TOC

-1

.76

-2.0

1 -2

.23

-2.3

4

-2.5

1 -2

.57

-2.7

5 -2

.79

-2.8

1 -2

.75

0135

A

HD

3.

82

2.06

1.

81

1.59

1.

48

1.

31

1.25

1.

07

1.03

1.

01

1.07

TO

C

-2.6

4 -2

.74

-2.8

0 -2

.86

-2.9

0 -2

.96

-2.9

7 -3

.10

-3.1

1 -3

.09

-3.0

3 01

36

AH

D

4.49

1.

85

1.75

1.

69

1.63

1.

59

1.53

1.

52

1.39

1.

38

1.40

1.

46

TOC

-0

.94

-1.2

0 -1

.30

-1.4

1 -1

.53

-1.5

8 -1

.52

-1.8

7 -1

.91

-1.8

1 -1

.56

0137

A

HD

4.

67

3.73

3.

47

3.37

3.

26

3.14

3.

09

3.15

2.

80

2.76

2.

86

3.11

TO

C

-1.3

9 -1

.44

-1.4

3 -1

.51

-1.5

8 -1

.60

-1.4

9 -1

.78

-1.7

7 -1

.67

-1.3

9 01

38

AH

D

6.40

5.

01

4.96

4.

97

4.89

4.

82

4.80

4.

91

4.62

4.

63

4.73

5.

01

TOC

-1

.13

-1.2

8 -1

.29

-1.4

1 -1

.46

-1.4

9 -1

.36

-1.6

4 -1

.57

-1.4

2 -1

.13

0139

A

HD

7.

14

6.01

5.

86

5.85

5.

73

5.68

5.

65

5.78

5.

50

5.57

5.

72

6.01

TO

C

-5.4

1 -5

.41

-5.5

8 -5

.57

-5.5

6 -5

.73

-5.7

7 -5

.89

-5.9

1 -5

.89

-5.8

8 01

40

AH

D

8.07

2.

66

2.66

2.

49

2.50

2.

51

2.34

2.

30

2.18

2.

16

2.18

2.

19

TOC

-0

.96

-0.9

9 -0

.99

-1.0

6 -1

.19

-1.1

8 -1

.08

-1.3

6 -1

.30

-1.1

9 -1

.01

0141

A

HD

8.

00

7.04

7.

01

7.01

6.

94

6.81

6.

82

6.92

6.

64

6.70

6.

81

6.99

TO

C

-1.1

5 -1

.25

-1.2

8 -1

.34

-1.4

1 -1

.39

-1.2

7 -1

.58

-1.4

8 -1

.36

-1.1

5 01

42

AH

D

8.69

7.

54

7.44

7.

41

7.35

7.

28

7.30

7.

42

7.11

7.

21

7.33

7.

54

TOC

-3

.87

-4.5

7 -5

.24

-5.1

9 -5

.02

-5.0

2 -4

.83

-4.8

2 -4

.98

-5.1

9 -5

.14

0143

A

HD

8.

45

4.58

3.

88

3.21

3.

26

3.43

3.

43

3.62

3.

63

3.47

3.

26

3.31


Gro

undw

ater

Lev

el (m

) W

ell N

o.

Gro

und

leve

l (m

) 21

/12/

01

10/1

/02

15/2

/02

22/3

/02

18/4

/02

25/7

/02

TOC

-1

.62

-1.5

9 -1

.84

-1.9

1 -1

.70

-1.5

3 01

31

AH

D

6.73

5.

11

5.14

4.

89

4.82

5.

03

5.20

TO

C

-1.3

4 -1

.32

-1.5

7 -1

.63

-1.2

6 -1

.19

0132

A

HD

6.

18

4.84

4.

86

4.61

4.

55

4.92

4.

99

TOC

-3

.11

-3.0

4 -3

.12

-3.1

5 -3

.07

-2.8

3 01

33

AH

D

5.71

2.

60

2.67

2.

59

2.56

2.

63

2.88

TO

C

-1.5

0 -1

.47

-1.7

2 -1

.75

-1.4

2 -1

.45

0134

A

HD

4.

73

3.23

3.

26

3.01

2.

98

3.31

3.

28

TOC

-2

.75

-2.7

4 -2

.90

-2.9

7 -2

.81

-2.3

1 01

35

AH

D

3.82

1.

07

1.08

0.

92

0.85

1.

01

1.51

TO

C

-2.9

2 -2

.90

-3.1

3 -3

.16

-2.9

6 -2

.70

0136

A

HD

4.

49

1.57

1.

59

1.36

1.

33

1.53

1.

79

TOC

-0

.94

-0.9

2 -1

.29

-1.0

6 -0

.77

-0.8

5 01

37

AH

D

4.67

3.

73

3.75

3.

38

3.61

3.

90

3.82

TO

C

-1.3

9 -1

.34

-1.4

4 -1

.36

-1.1

5 -1

.30

0138

A

HD

6.

40

5.01

5.

06

4.96

5.

04

5.25

5.

10

TOC

-1

.15

-1.1

3 -1

.36

-1.2

8 -1

.18

-1.1

0 01

39

AH

D

7.14

5.

99

6.01

5.

78

5.87

5.

97

6.04

TO

C

-5.8

4 -5

.84

-5.9

4 -5

.99

-5.9

9 -5

.81

0140

A

HD

8.

07

2.23

2.

23

2.13

2.

08

2.08

2.

26

TOC

-1

.12

-1.0

9 -1

.30

-1.2

4 -1

.00

-1.1

6 01

41

AH

D

8.00

6.

88

6.91

6.

70

6.76

7.

00

6.84

TO

C

-1.3

1 -1

.27

-1.5

4 -1

.51

-1.4

3 -1

.47

0142

A

HD

8.

69

7.38

7.

42

7.15

7.

18

7.26

7.

22

TOC

-4

.70

-4.6

2 -4

.70

-4.7

7 -4

.67

-4.7

7 01

43

AH

D

8.45

3.

75

3.83

3.

75

3.68

3.

78

3.68


Gro

undw

ater

Lev

el (m

) W

ell N

o.

Gro

und

leve

l (m

) 10

/4/0

1 1/

5/01

22

/5/0

1 5/

6/01

15

/6/0

1 3/

7/01

1/

8/01

19

/9/0

1 12

/10/

01

19/1

0/01

13

/11/

01

TOC

-2

.10

-2.1

5 -2

.21

-2.2

8 -2

.32

-2.3

8 -2

.36

-2.8

3 -2

.96

-2.8

7 -2

.69

0144

A

HD

4.

25

2.15

2.

10

2.04

1.

97

1.93

1.

87

1.89

1.

42

1.29

1.

38

1.56

TO

C

-1.3

4 -1

.34

-1.2

9 -1

.36

-1.4

0 -1

.40

-1.3

4 -1

.53

-1.4

9 -1

.37

-1.2

8 01

45

AH

D

4.41

3.

07

3.07

3.

12

3.05

3.

01

3.01

3.

07

2.88

2.

92

3.04

3.

13

TOC

-1

.45

-1.5

2 -1

.54

-1.6

3 -1

.71

-1.7

5 -1

.76

-2.1

5 -2

.26

-2.2

5 -2

.09

0146

A

HD

4.

08

2.63

2.

56

2.54

2.

45

2.37

2.

33

2.32

1.

93

1.82

1.

83

1.99

TO

C

-2.1

0 -2

.07

-2.1

1 -2

.17

-2.2

3 -2

.27

-2.2

5 -2

.70

-2.7

9 -2

.71

-2.6

3 01

47

AH

D

4.13

2.

03

2.06

2.

02

1.96

1.

90

1.86

1.

88

1.43

1.

34

1.42

1.

50

TOC

-4

.16

-4.3

0 -4

.39

-4.4

4 -4

.50

-4.5

6 -4

.60

-4.9

6 -5

.02

-4.9

8 -4

.91

0148

A

HD

6.

83

2.67

2.

53

2.44

2.

39

2.33

2.

27

2.23

1.

87

1.81

1.

85

1.92

TO

C

-0.9

4 -1

.05

-0.9

3 -1

.16

-1.2

4 -1

.20

-1.1

2 -1

.47

-1.5

6 -1

.48

-1.2

9 01

49

AH

D

5.18

4.

24

4.13

4.

25

4.02

3.

94

3.98

4.

06

3.71

3.

62

3.70

3.

89

TOC

-2

.01

-2.5

8 -2

.79

-2.1

5 -2

.10

-2.2

6 -2

.40

-2.8

6 -3

.11

-2.9

8 -2

.88

0150

A

HD

5.

24

3.23

2.

66

2.45

3.

09

3.14

2.

98

2.84

2.

38

2.13

2.

26

2.36

TO

C

-3.2

4 -3

.36

-3.4

1 -3

.48

-3.5

2 -3

.56

-3.5

6 -3

.95

-4.0

3 -3

.98

-3.9

2 01

51

AH

D

5.19

1.

95

1.83

1.

78

1.71

1.

67

1.63

1.

63

1.24

1.

16

1.21

1.

27


Gro

undw

ater

Lev

el (m

) W

ell N

o.

Gro

und

leve

l (m

) 21

/12/

01

10/1

/02

15/2

/02

22/3

/02

18/4

/02

25/7

/02

TOC

-2

.80

-2.8

0 -3

.39

-3.5

3 -3

.12

-2.9

6 01

44

AH

D

4.25

1.

45

1.45

0.

87

0.72

1.

14

1.29

TO

C

-1.4

2 -1

.39

-1.5

6 -1

.56

-1.4

8 -1

.50

0145

A

HD

4.

41

2.99

3.

02

2.85

2.

85

2.93

2.

91

TOC

-2

.35

-2.3

0 -2

.58

-2.5

6 -2

.45

-2.3

9 01

46

AH

D

4.08

1.

73

1.78

1.

50

1.52

1.

63

1.69

TO

C

-2.8

5 -2

.83

-3.2

7 -3

.38

-3.1

1 -3

.00

0147

A

HD

4.

13

1.28

1.

30

0.86

0.

75

1.02

1.

13

TOC

-5

.03

-4.9

9 -5

.36

-5.4

4 -5

.20

-5.1

8 01

48

AH

D

6.83

1.

80

1.84

1.

48

1.39

1.

63

1.65

TO

C

-1.4

1 -1

.35

-1.6

2 -1

.59

-1.4

4 -1

.40

0149

A

HD

5.

18

3.77

3.

83

3.56

3.

59

3.74

3.

78

TOC

-3

.07

-3.0

2 -3

.32

-3.2

9 -3

.05

-2.2

8 01

50

AH

D

5.24

2.

17

2.22

1.

92

1.95

2.

19

2.96

TO

C

-4.0

6 -4

.03

-4.3

9 -4

.49

-4.3

5 -4

.17

0151

A

HD

5.

19

1.13

1.

16

0.80

0.

70

0.85

1.

02


Appendix G

Physico-chemical Data

Appendix G – physico-chemical data

Well No. Date Water

level Water level D.O. Cond. pH Eh Temp Colour

(m bgl) (m AHD) (ppm) (uS/cm) (mV) (oC) Wells screened within palaeochannel aquifer

089 22/08/00 -3.32 2.31 0.0 395 5.9 134 23 Nil 089 4/09/00 -3.38 2.25 4.5 390 5.7 247 23 Nil 089 10/10/00 -3.51 2.12 0.0 386 5.5 256 23 Nil 089 7/11/00 -3.46 2.17 1.1 387 5.9 285 23 Slight 089 1/05/01 -3.52 2.11 0.7 371 5.8 165 23 Nil 089 19/09/01 -3.88 1.75 0.8 364 5.9 186 21 Nil 089 12/10/01 -3.90 1.73 0.6 364 5.7 226 21 Nil 089 25/07/02 -3.50 2.13 2.0 408 5.0 142 23 Nil 136 1/05/01 -2.34 1.75 0.1 268 4.5 278 23 Slight 136 5/06/01 -2.46 1.63 1.0 291 4.5 253 23 Slight 136 19/09/01 -2.70 1.39 0.6 270 4.7 187 21 Slight 136 12/10/01 -2.71 1.38 0.6 285 4.9 233 22 Slight 136 25/07/02 -2.30 1.79 1.4 306 5.0 223 23 Slight

Wells screened within sandy silt aquifer 088 22/08/00 -6.07 2.49 0.2 354 5.7 195 22 Nil 088 4/09/00 -6.10 2.46 0.8 374 6.6 192 23 Nil 088 10/10/00 -6.23 2.34 0.7 349 5.9 190 24 Nil 088 7/11/00 -6.16 2.40 0.8 348 5.9 230 23 Nil 088 1/05/01 -6.14 2.42 0.8 336 6.0 155 23 Nil 088 19/09/01 -6.49 2.07 0.8 326 5.6 214 22 Nil 088 12/10/01 -6.53 2.03 0.8 311 5.8 198 21 Nil 088 25/07/02 -6.48 2.08 0.6 309 6.0 137 23 Nil 140 1/05/01 -4.96 2.66 0.6 3 4.9 279 23 Dark 140 19/09/01 -5.44 2.18 0.7 289 5.0 225 21 Medium 140 12/10/01 -5.46 2.16 0.7 278 5.2 285 22 Slight 140 25/07/02 -5.36 2.26 0.4 328 5.3 217 23 Slight 144 5/06/01 -1.87 1.97 0.6 1119 5.7 198 21 Slight 144 19/09/01 -2.42 1.42 0.7 1109 5.5 177 21 Medium 144 12/10/01 -2.55 1.29 0.6 1106 5.6 183 20 Slight 144 25/07/02 -2.55 1.29 0.6 1359 5.4 213 22 Medium 147 22/05/01 -1.72 2.02 5.1 81 5.9 280 23 Medium 147 5/06/01 -1.78 1.96 1.0 109 5.1 256 22 Medium 147 19/09/01 -2.31 1.43 0.4 49 4.8 218 21 Medium 147 12/10/01 -2.40 1.34 0.7 58 5.0 271 22 Slight 147 25/07/02 -2.61 1.13 0.9 91 4.8 240 19 Slight 148 19/09/01 -4.61 1.87 0.6 65 4.5 333 22 Nil 148 25/07/02 -4.83 1.65 0.9 83 4.6 282 23 Slight 151 22/05/01 -2.94 1.78 0.1 225 4.1 304 23 Medium 151 19/09/01 -3.48 1.24 0.4 262 4.3 277 21 Medium 151 25/07/02 -3.70 1.02 1.0 251 4.4 262 22 Medium

Wells screened within shoreface brown sand aquifer 100 22/08/00 -2.88 2.8 2.5 400 4.7 90 23 Slight 100 4/09/00 -2.91 2.77 0.3 389 4.5 230 23 Slight 100 10/10/00 -2.95 2.73 0.0 373 4.9 271 23 Medium 100 7/11/00 -2.93 2.75 3.6 375 4.9 273 23 Medium 100 1/05/01 -3.06 2.62 0.5 333 4.5 243 23 Medium 100 19/09/01 -3.46 2.22 0.5 351 4.9 203 21 Medium 100 12/10/01 -3.44 2.24 0.6 342 4.6 234 21 Medium


Well No. Date Water


(m bgl) (m AHD) (ppm) (uS/cm) (mV) (oC) 100 25/07/02 -3.15 2.53 1.2 354 5.0 22 22 Medium 101 22/08/00 -5.99 2.5 0.1 177 3.5 368 23 Strong 101 4/09/00 -6.06 2.43 0.7 148 4.7 226 23 Medium 101 10/10/00 -6.15 2.34 0.7 123 4.9 266 23 Medium 101 7/11/00 -6.07 2.42 0.0 149 4.8 165 23 Medium 101 1/05/01 -5.99 2.5 0.8 60 4.5 286 23 Slight 101 19/09/01 -6.47 2.02 0.5 118 4.5 236 22 Medium 101 12/10/01 -6.48 2.01 0.4 111 4.7 265 21 Slight 101 25/07/02 -6.43 2.06 0.9 192 4.7 225 23 Slight

MW4D 19/09/01 -4.64 0.57 0.5 341 5.3 272 21 Slight MW5D 19/09/01 -4.21 0.81 1.6 251 5.1 302 21 Nil MW6D 19/09/01 -5.26 1.05 0.5 316 5.5 238 21 Medium MW7D 19/09/01 -5.46 1.24 0.6 287 5.3 241 21 Medium MW8D 19/09/01 -5.90 1.86 0.5 338 5.0 271 21 Medium Wells screened within indurated sand

143 1/05/01 -4.20 3.88 0.1 56 4.0 326 24 V.dark 143 19/09/01 -4.45 3.63 0.5 72 3.8 288 21 V.dark 143 12/10/01 -4.61 3.47 0.6 84 3.9 329 21 V.dark 143 25/07/02 -4.40 3.68 3.0 108 3.9 302 23 V.dark 150 22/05/01 -2.34 2.45 0.5 335 3.1 314 23 V.dark 150 19/09/01 -2.41 2.38 1.2 262 3.5 300 18 V.dark 150 12/10/01 -2.66 2.13 1.0 247 3.6 312 19 V.dark 150 25/07/02 -1.83 2.96 4.0 267 3.5 314 19 V.dark

Wells screened within foreshore and beach sand aquifer 114 10/10/00 -0.90 4.20 3.6 193 3.8 339 22 Dark 114 7/11/00 -0.61 4.48 3.7 230 4.0 339 23 Dark 114 19/09/01 -0.89 4.20 0.9 245 3.7 206 20 V.dark 115 21/08/00 -0.45 5.86 3.6 354 3.4 120 21 Dark 115 4/09/00 -0.55 5.76 0.4 372 3.1 300 21 Dark 115 9/10/00 -0.79 5.52 3.4 371 3.6 356 22 Dark 115 7/11/00 -0.56 5.75 3.4 356 3.8 350 22 Dark 115 19/09/01 -0.85 5.46 0.9 336 3.6 248 20 V.dark 115 25/07/02 -0.66 5.65 4.0 338 3.4 281 21 V.dark 126 22/08/00 -2.79 3.68 4.3 85 4.9 231 21 V.dark 126 4/09/00 -2.85 3.62 4.4 81 4.5 387 22 V.dark 126 10/10/00 -3.03 3.44 3.7 77 4.5 410 23 V.dark 126 7/11/00 -2.84 3.63 3.7 73 4.7 354 23 V. dark 126 19/09/01 -3.19 3.28 0.4 75 4.3 350 21 V. dark 126 25/07/02 -3.19 3.28 3.2 78 4.4 342 25 V.dark 129 19/09/01 -1.66 1.66 0.4 87 4.1 375 19 Dark 129 12/10/01 -1.56 1.56 0.6 100 4.2 521 20 Dark 129 25/07/02 -1.20 1.20 3.6 85 4.4 374 19 V.dark 131 5/06/01 -0.99 5.34 3.0 90 4.1 302 24 V.dark 131 19/09/01 -1.33 5.00 0.9 53 4.2 295 20 V.dark 131 25/07/02 -1.13 5.20 3.2 67 4.2 306 21 Dark 132 5/06/01 -0.62 5.08 2.6 280 3.9 223 23 V.dark 132 19/09/01 -1.00 4.70 0.7 252 3.8 202 19 V.dark 132 25/07/02 -0.71 4.99 3.3 314 3.8 264 20 V.dark 133 19/09/01 -2.69 2.63 2.1 292 3.5 204 17 V.dark


Well No. Date Water


(m bgl) (m AHD) (ppm) (uS/cm) (mV) (oC) 133 25/07/02 -2.44 2.88 6.6 417 3.4 307 18 V.dark 134 5/06/01 -0.89 3.41 3.1 250 4.5 265 23 V.dark 134 19/09/01 -1.19 3.11 0.7 232 3.8 259 18 V.dark 134 25/07/02 -1.02 3.28 3.5 314 3.7 274 18 V.dark 135 5/06/01 -1.69 1.48 3.4 577 3.4 294 22 Medium 135 19/09/01 -2.10 1.07 0.7 295 3.8 240 19 Medium 135 25/07/02 -1.66 1.51 3.6 568 3.6 288 19 Medium 137 1/05/01 -0.69 3.47 0.4 235 3.8 318 24 Medium 137 5/06/01 -0.90 3.26 4.4 265 4.0 292 21 Medium 137 19/09/01 -1.36 2.80 3.4 230 4.0 271 18 V.dark 137 12/10/01 -1.40 2.76 4.4 231 4.4 277 20 Medium 137 25/07/02 -0.34 3.82 4.6 381 3.9 319 17 V.dark 138 1/05/01 -0.83 4.96 0.8 196 3.8 293 25 V. dark 138 5/06/01 -0.90 4.89 4.7 254 3.1 278 22 V.dark 138 19/09/01 -1.17 4.62 0.6 245 3.7 207 19 V.dark 138 12/10/01 -1.16 4.63 0.6 235 3.8 238 20 V.dark 138 25/07/02 -0.69 5.10 5.0 295 3.8 300 20 V.dark 139 1/05/01 -0.80 5.86 0.8 344 4.3 255 25 V.dark 139 5/06/01 -0.93 5.73 3.4 334 4.4 243 23 V.dark 139 19/09/01 -1.16 5.50 0.5 291 4.3 185 20 V.dark 139 25/07/02 -0.62 6.04 3.7 332 4.5 264 20 V.dark 141 1/05/01 -0.52 7.01 4.5 82 4.0 313 24 V.dark 141 5/06/01 -0.59 6.94 4.5 97 4.4 273 19 V.dark 141 19/09/01 -0.89 6.64 1.3 99 4.2 267 19 Dark 141 12/10/01 -0.83 6.70 0.7 103 4.4 300 20 V.dark 141 25/07/02 -0.69 6.84 4.4 163 4.6 267 19 V.dark 142 1/05/01 -0.75 7.44 0.8 53 3.8 322 25 V.dark 142 5/06/01 -0.84 7.35 3.1 80 4.1 313 22 V.dark 142 19/09/01 -1.08 7.11 0.5 71 3.9 281 19 V.dark 142 12/10/01 -0.98 7.21 0.7 71 4.0 323 20 V.dark 142 25/07/02 -0.97 7.22 3.1 102 3.9 298 20 V.dark 145 5/06/01 -0.91 3.05 3.9 185 3.5 357 23 V.dark 145 19/09/01 -1.08 2.88 0.8 162 3.6 317 19 V.dark 145 12/10/01 -1.04 2.92 1.4 138 3.7 336 19 V.dark 145 25/07/02 -1.05 2.91 4.8 198 3.5 345 18 V.dark 146 22/05/01 -1.13 2.54 2.9 46 5.6 276 26 V.dark 146 5/06/01 -1.22 2.45 3.8 69 4.4 276 24 V.dark 146 19/09/01 -1.74 1.93 3.6 57 4.3 255 23 V.dark 146 12/10/01 -1.85 1.82 3.1 57 4.6 293 23 V.dark 146 25/07/02 -1.98 1.69 4.7 74 4.4 274 23 V.dark 149 22/05/01 -0.55 4.25 3.6 195 3.4 370 24 V.dark 149 5/06/01 -0.78 4.02 2.9 275 3.4 362 22 V.dark 149 19/09/01 -1.09 3.71 1.1 201 3.5 327 18 V.dark 149 25/07/02 -1.02 3.78 2.6 249 3.2 346 18 V.dark

MW2S 19/09/01 -1.51 5.25 3.4 248 4.2 304 19 V.dark MW3S 19/09/01 -1.18 5.15 0.5 174 4.8 247 19 Dark MW4S 19/09/01 -2.03 2.87 4.6 265 3.6 410 22 V.dark MW5S 19/09/01 -1.59 3.35 2.8 387 3.9 338 21 V.dark MW6S 19/09/01 -0.46 6.01 0.5 180 4.1 293 19 V.dark


Well No. Date Water


(m bgl) (m AHD) (ppm) (uS/cm) (mV) (oC) MW8S 19/09/01 -1.58 6.01 0.6 102 3.9 339 21 Dark Surface water

S1 21/08/00 2.3 292 3.2 290 17 Strong S1 7/11/00 5.1 386 3.5 556 26 Dark S5 28/08/00 5.4 209 3.4 293 15 Dark S5 5/09/00 6.5 213 3.1 468 24 V.dark S5 10/10/00 6.2 209 3.6 434 27 V.dark S5 7/11/00 4.3 168 3.9 432 25 V.dark S5 5/07/01 5.1 280 3.6 417 22 V.dark S6 5/09/00 5.9 176 3.1 502 28 V.dark S6 10/10/00 4.4 238 3.5 465 27 V.dark S6 7/11/00 5.1 162 3.6 451 30 v.dark S9 4/09/00 7.3 44400 7.0 383 25 Slight

S10 5/09/00 4.0 87 3.6 473 24 V.dark S10 10/10/00 3.9 97 3.8 409 28 V.dark S10 7/11/00 5.3 124 3.7 408 24 V.dark S10 5/07/01 5.1 177 3.5 417 19 V.dark S11 5/09/00 4.7 198 3.3 536 22 V.dark S11 10/10/00 5.6 283 3.4 497 31 V.dark S11 7/11/00 3.2 184 3.6 458 24 V.dark S11 5/07/01 4.8 239 3.4 430 18 V.dark S12 5/09/00 8.4 194 4.3 453 23 Slight S12 7/11/00 7.2 88 4.9 440 28 V.slight S13 5/09/00 4.3 162 3.7 543 23 V.dark S13 10/10/00 4.8 159 3.6 526 28 V.dark S13 7/11/00 4.0 151 3.6 522 22 v.dark S14 5/09/00 3.4 291 2.9 576 25 V.dark S14 7/11/00 2.6 314 3.4 556 25 V.dark S15 5/09/00 5.4 254 3.3 556 23 V.dark S15 10/10/00 1.5 234 3.8 428 26 V.dark S15 7/11/00 2.0 271 3.8 416 25 V.dark S15 5/07/01 4.3 320 3.5 4.54 15 V.dark S16 5/09/00 6.0 302 3.3 532 19 V.dark S16 10/10/00 6.2 352 3.6 460 33 V.dark S16 7/11/00 4.0 349 3.6 473 28 V.dark S16 5/07/01 4.4 428 3.7 361 17 V.dark S17 6/09/00 4.4 516 3.5 562 20 V.slight

S17 10/10/00 1.7 514 3.8 521 24 slight-med

S17 7/11/00 3.0 517 3.7 530 22 Med S18 6/09/00 3.7 101 3.5 565 23 Dark S18 10/10/00 4.3 101 3.8 506 30 V.dark S18 7/11/00 6.1 137 3.8 512 27 V.dark S19 6/09/00 2.1 159 3.4 563 25 V.dark S19 10/10/00 5.1 131 3.7 492 28 V.dark S19 7/11/00 3.4 131 3.8 474 25 V.dark S19 5/07/01 3.6 150 3.7 438 19 V.dark S20 6/09/00 6.8 98 3.4 562 24 V.dark S20 10/10/00 4.7 103 3.8 470 29 V.dark


Well No. Date Water


(m bgl) (m AHD) (ppm) (uS/cm) (mV) (oC) S20 7/11/00 6.7 111 3.7 536 25 V.dark S20 5/07/01 5.4 100 3.7 400 23 V.dark S21 10/10/00 5.2 741 3.9 470 33 Dark S22 10/10/00 3.1 57 4.3 465 27 Dark S22 7/11/00 1.4 79 4.2 382 23 Dark S23 5/07/01 4.0 215 3.4 419 19 V.dark S24 5/07/01 5.4 363 3.3 397 21 V.dark S25 5/07/01 5.8 377 3.7 368 21 V.dark S26 5/07/01 6.2 585 3.7 378 20 V.dark S27 5/07/01 10.7 378 3.7 366 22 V.dark S28 5/07/01 8.2 573 3.4 376 22 V.dark S29 5/07/01 4.9 396 3.3 4.11 23 V.dark S30 5/07/01 1.6 191 3.5 400 21 Medium S31 5/07/01 5.8 354 3.2 421 20 V.dark S32 5/07/01 5.0 257 3.7 350 18 V.dark S33 5/07/01 3.3 248 3.8 362 20 V.dark

Appendix H

Major and Minor Ion Chemistry

Wel

l No.

D

ate

pH

Con

d.

Na

Mg

Ca

K

Cl

HC

O3

SO4

DO

C

SiO

2 M

n Fe

Zn

C

u B

r A

l

uS/

cm

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L W

ells

scre

ened

with

in p

alae

ocha

nnel

aqu

ifer

089

01-F

eb-9

2 5.

1 41

0 53

9.

0 12

.0

5.9

80

105

0.0

14

0.

2 6.

9

08

9 01

-Mar

-92

6.2

830

81

33.0

51

.0

4.3

72

450

0.0

24

8.

6 13

.0

089

09-S

ep-9

5 7.

6 45

4 52

14

.0

20.0

3.

7 69

16

0 0.

0

21

3.0

0.2

0.00

0.

06

0.

00

089

08-A

ug-9

6 6.

1 56

5 46

8.

7 16

.0

4.1

66

110

0.0

19

1.

8 0.

0 0.

01

0.00

0.00

08

9 14

-Sep

-00

5.7

390

44

6.6

11.1

4.

7 63

88

.3

0.1

0.9

15.9

0.

02

0.00

0.

15

0.00

08

9 19

-Sep

-01

5.9

364

44

6.8

11.2

5.

1 61

11

0 0.

6

28

0.8

16.4

0.

03

0.01

0.

18

0.14

08

9 30

-Jul

-02

5.0

408

44

6.8

9.8

4.4

61

60

0.6

22

27

0.5

13.5

0.

02

0.01

0.

18

0.05

13

6 05

-Jun

-01

4.5

291

45

4.7

4.0

4.9

74

2.9

4.2

5

0.1

6.8

0.04

4.

86

0.13

0.

20

136

19-S

ep-0

1 4.

7 27

0 62

5.

1 1.

6 2.

9 84

20

2.

4 51

17

0.

0 2.

0 0.

04

0.01

0.

24

0.41

13

6 30

-Jul

-02

5.0

306

43

4.3

2.5

3.4

78

10.5

0.

0 26

18

0.

0 3.

0 0.

06

0.01

0.

12

0.26

W

ells

scre

ened

with

in sa

ndy

silt

aqui

fer

08

8 01

-Feb

-92

6.6

385

57

6.0

7.7

4.3

68

98

2.2

17

0.

1 5.

0

08

8 01

-Mar

-92

6.4

420

64

8.2

14.0

5.

3 82

12

5 4.

5

20

0.3

9.0

088

09-S

ep-9

5 7.

1 32

0 49

7.

1 8.

7 4.

6 50

10

5 0.

0

16

0.0

0.3

0.03

0.

08

0.

00

088

08-A

ug-9

6 6.

0 33

2 51

6.

9 6.

4 4.

9 46

11

0 0.

0

16

0.0

0.1

0.03

0.

00

0.

00

088

14-S

ep-0

0 6.

6 37

4 49

6.

8 6.

2 5.

3 46

99

.8

0.2

0.0

12.2

0.

04

0.00

0.

11

0.02

08

8 19

-Sep

-01

5.6

326

49

7.0

6.6

5.4

52

120

1.4

24

0.

0 12

.4

0.03

0.

01

0.12

0.

00

088

30-J

ul-0

2 6.

0 30

9 49

6.

2 6.

1 4.

3 43

80

0.

7 42

26

0.

0 10

.8

0.01

0.

01

0.12

0.

02

140

19-S

ep-0

1 5.

0 28

9 45

5.

1 2.

8 3.

2 77

27

2.

2 22

20

0.

0 5.

8 0.

03

0.00

0.

15

0.35

14

0 30

-Jul

-02

5.3

328

44

4.0

2.8

3.7

73

23

2.2

20

0.

0 4.

9 0.

02

0.01

0.

20

0.16

14

4 05

-Jun

-01

5.7

1119

16

6 20

.4

12.4

10

.1

257

2.43

79

.8

20

0.

1 7.

8 0.

02

0.00

0.

67

0.15

14

4 19

-Sep

-01

5.5

1109

93

13

.3

7.9

9.7

54

180

17.6

20

0.1

5.4

0.00

0.

00

0.14

0.

20

144

30-J

ul-0

2 5.

4 13

59

177

24.4

14

.4

9.8

455

40

194.

7 38

21

0.

1 8.

5 0.

03

0.01

1.

81

0.19

14

7 05

-Jun

-01

5.1

81

16

2.0

1.7

1.7

24

2.23

1.

4

9 0.

0 1.

2 0.

05

0.00

0.

10

0.66

14

7 19

-Sep

-01

4.8

50

5 0.

9 0.

5 1.

6 11

4.

1 0.

7 30

9

0.0

0.4

0.02

0.

01

0.06

1.

33

Appendix G – major and minor ion chemistry

Wel

l No.

D

ate

pH

Con

d.

Na

Mg

Ca

K

Cl

HC

O3

SO4

DO

C

SiO

2 M

n Fe

Zn

C

u B

r A

l

uS/

cm

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L 14

7 30

-Jul

-02

4.8

91

11

2.0

1.4

1.2

24

0 3.

1 33

9

0.0

0.9

0.04

0.

01

0.12

0.

86

148

19-S

ep-0

1 4.

5 65

14

1.

5 0.

3 0.

2 22

5.

3 0.

8

13

0.0

0.3

0.00

0.

01

0.09

0.

38

148

30-J

ul-0

2 4.

6 83

11

1.

4 0.

5 1.

3 21

0

14.8

29

14

0.

0 0.

3 0.

02

0.01

0.

09

0.52

15

1 19

-Sep

-01

4.3

262

55

3.6

1.9

3.0

64

0 0.

4

14

0.1

2.4

0.09

0.

01

0.20

0.

76

151

30-J

ul-0

2 4.

4 25

1 36

2.

8 1.

8 1.

3 59

0

6.5

84

15

0.0

1.6

0.03

0.

01

0.18

0.

58

Wel

ls sc

reen

ed w

ithin

shor

efac

e br

own

sand

aq

uife

r

100

01-F

eb-9

2 4.

7 40

0 57

9.

0 6.

4 2.

5 10

5 30

2.

0

12

0.1

0.2

100

01-M

ar-9

2 4.

8 34

5 53

6.

9 2.

9 1.

2 89

22

0.

0

12

0.1

2.7

100

09-S

ep-9

5 5.

2 32

8 52

5.

8 2.

3 1.

6 90

15

2.

9

12

0.0

0.3

0.12

0.

04

1.

06

100

08-A

ug-9

6 4.

9 34

9 53

7.

0 2.

9 1.

3 92

15

0.

0

12

0.0

0.5

0.10

0.

00

1.

62

100

14-S

ep-0

0 4.

5 38

9 55

8.

0 1.

0 1.

4 99

18

0.

7

0.

0 0.

7 0.

00

0.00

0.

31

1.92

10

0 19

-Sep

-01

4.9

351

55

4.3

0.8

2.3

102

10

0.6

15

0.

0 0.

4 0.

04

0.00

0.

25

1.49

10

0 30

-Jul

-02

5.0

354

50

6.4

1.2

1.5

87

7.5

37.0

1

17

0.0

0.4

0.03

0.

01

0.23

1.

78

101

01-F

eb-9

2 4.

4 33

0 41

8.

2 10

.0

2.4

77

26

2.0

6

0.1

0.7

101

01-M

ar-9

2 4.

6 17

0 24

5.

3 5.

0 1.

3 30

26

0.

0

7 0.

1 3.

5

10

1 09

-Sep

-95

4.6

108

11

3.2

0.9

0.6

22

9.2

1.5

4

0.0

0.6

0.20

0.

06

1.

08

101

08-A

ug-9

6 4.

7 11

2 14

2.

5 1.

9 0.

5 28

5.

2 3.

0

6 0.

0 0.

5 0.

04

0.01

1.54

10

1 14

-Sep

-00

4.7

148

23

2.7

0.8

1.2

37

9 0.

7

0.

0 1.

7 0.

01

0.00

0.

11

1.55

10

1 19

-Sep

-01

4.5

118

16

2.9

0.6

0.2

31

10

0.3

11

0.

0 3.

4 0.

04

0.02

0.

10

1.73

10

1 30

-Jul

-02

4.7

192

28

3.1

1.1

1.5

44

0.5

0.6

41

13

0.0

1.5

0.05

0.

01

0.13

1.

14

MW

3D

26-A

pr-0

0 5.

4 34

4 50

4.

00

2.00

2.

00

85

20.0

0 0.

50

0.1

5.9

5.

10

MW

3D

17-J

ul-0

0

48

4.

00

3.00

3.

00

83

10.0

0 1.

00

0.0

9.8

1.

00

MW

4D

26-A

pr-0

0 5.

4 35

1 52

4.

00

3.00

3.

00

88

20.0

0 0.

50

0.0

9.3

0.

70

MW

4D

17-J

ul-0

0

49

5.

00

5.00

4.

00

88

9.00

7.

00

0.0

2.2

0.

13

MW

4D

19-S

ep-0

1 5.

3 34

1 50

4.

34

3.60

4.

33

92

19.0

0 0.

36

18

0.

0 10

.0

0.03

0.

01

0.22

0.

10


Wel

l No.

D

ate

pH

Con

d.

Na

Mg

Ca

K

Cl

HC

O3

SO4

DO

C

SiO

2 M

n Fe

Zn

C

u B

r A

l

uS/

cm

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L M

W5D

19

-Sep

-01

5.1

251

41

3.18

1.

82

3.57

67

18

.00

0.63

18

0.0

3.5

0.02

0.

00

0.15

0.

20

MW

6D

19-S

ep-0

1 5.

5 31

6 45

5.

38

5.41

5.

20

76

27.0

0 0.

22

22

0.

1 7.

3 0.

03

0.00

0.

16

0.06

M

W7D

19

-Sep

-01

5.3

287

51

4.44

3.

26

0.02

78

32

.00

0.44

18

0.0

10.1

0.

03

0.02

0.

17

0.14

M

W8D

19

-Sep

-01

5.0

338

53

5.12

1.

71

3.23

96

20

.00

2.23

4 0.

0 6.

1 0.

02

0.00

0.

24

0.29

W

ells

scre

ened

with

in in

dura

ted

sand

143

05-J

un-0

1 4.

0 56

7

1.2

0.8

0.3

9 0

0.6

12

0.

0 0.

3 0.

05

0.00

0.

06

0.23

14

3 19

-Sep

-01

3.8

72

7 1.

5 0.

5 0.

4 11

0

1.3

137

9 0.

0 1.

5 0.

01

0.02

0.

06

1.26

14

3 30

-Jul

-02

3.9

108

8 4.

1 1.

9 2.

0 12

0

2.9

91

13

0.0

0.6

0.29

0.

01

0.12

1.

91

150

19-S

ep-0

1 3.

5 26

2 30

4.

5 1.

9 0.

7 45

2

1.1

6

0.0

1.0

0.03

0.

01

0.14

1.

80

150

30-J

ul-0

2 3.

5 26

7 25

5.

4 3.

1 0.

8 43

0

3.2

171

7 0.

0 1.

0 0.

16

0.01

0.

16

2.37

W

ells

scre

ened

with

in fo

resh

ore

and

beac

h sa

nd a

quife

r

11

4 09

-Sep

-95

4.5

140

18

2.8

4.1

1.1

29

3.6

1.2

5

0.0

0.3

0.13

0.

08

0.

36

114

08-J

ul-9

6 4.

0 14

5 18

3.

1 1.

9 0.

5 30

6.

7 0.

4

5 0.

0 0.

3 0.

03

0.01

0.35

11

4 19

-Sep

-01

3.7

245

30

6.3

0.6

1.3

51

4.6

4.4

5

0.0

0.4

0.01

0.

01

0.16

0.

51

115

09-S

ep-9

5 4.

0 14

5 20

1.

5 1.

4 0.

7 27

0

0.6

0.0

0.2

0.14

0.

06

0.

45

115

07-A

ug-9

6 3.

6 21

7 20

1.

8 0.

3 0.

5 27

0

0.0

6

0.0

0.2

0.06

0.

01

0.

68

115

14-S

ep-0

0 3.

1 37

2 40

7.

0 0.

8 2.

6 76

0

2.1

8

0.0

0.5

0.10

0.

00

0.24

0.

93

115

15-N

ov-0

0 3.

3

40

6.4

0.7

0.8

78

0 1.

2

7 0.

0 0.

7 0.

01

0.00

0.

25

0.76

11

5 19

-Sep

-01

3.6

336

36

5.9

0.4

1.7

70

0 1.

4 11

3 7

0.0

0.3

0.05

0.

01

0.21

0.

66

115

30-J

ul-0

2 3.

4 33

8 34

5.

3 0.

6 0.

8 65

0

2.1

84

9 0.

0 0.

4 0.

03

0.01

0.

26

0.73

12

6 14

-Sep

-00

4.5

81

11

1.7

5.0

0.7

12

0 3.

6

0.

1 4.

4 0.

14

0.00

0.

04

0.92

12

6 15

-Nov

-00

4.8

10

1.

9 5.

4 1.

0 12

0

3.0

3

0.0

3.4

0.01

0.

00

0.04

0.

52

126

19-S

ep-0

1 4.

3 75

10

1.

9 3.

4 0.

8 12

0

2.7

81

4 0.

0 3.

3 0.

04

0.03

0.

07

0.68

12

6 30

-Jul

-02

4.4

78

8 2.

7 4.

6 0.

0 11

0

3.2

104

7 0.

0 4.

3 0.

08

0.01

2.03

12

9 19

-Sep

-01

4.1

87

10

2.3

6.0

0.6

20

0.8

4.9

4

0.0

0.2

0.02

0.

01

0.05

0.

45

129

30-J

ul-0

2 4.

4 85

8

3.1

9.4

0.9

11

0 3.

8 55

8

0.0

0.9

0.06

0.

01

0.

92


Wel

l No.

D

ate

pH

Con

d.

Na

Mg

Ca

K

Cl

HC

O3

SO4

DO

C

SiO

2 M

n Fe

Zn

C

u B

r A

l

uS/

cm

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L 13

1 05

-Jun

-01

4.1

90

11

1.3

0.9

0.0

13

0 0.

8

4 0.

0 0.

7 0.

05

0.00

0.

05

0.51

13

1 19

-Sep

-01

4.2

53

9 1.

2 1.

0 0.

0 20

0

1.6

89

5 0.

0 0.

8 0.

02

0.00

0.

08

0.68

13

1 30

-Jul

-02

4.2

67

8 2.

6 2.

2 1.

0 10

0

1.7

59

7 0.

0 1.

2 0.

09

0.02

0.57

13

2 05

-Jun

-01

3.9

280

38

7.9

0.7

0.1

254

0 78

.9

135

9 0.

0 1.

1 0.

14

0.00

0.

65

2.18

13

2 19

-Sep

-01

3.8

252

19

4.9

0.3

0.4

52

0 1.

1 21

1 9

0.0

0.4

0.03

0.

01

0.31

1.

75

132

30-J

ul-0

2 3.

7 31

4 34

9.

8 0.

7 0.

0 61

0

1.3

9

0.0

0.6

0.07

0.

01

0.41

2.

45

133

19-S

ep-0

1 3.

5 29

2 36

5.

1 1.

2 1.

3 50

1.

3 0.

3

3 0.

1 1.

5 0.

04

0.01

0.

06

1.04

13

3 30

-Jul

-02

3.4

417

44

8.7

1.9

0.7

82

0 6.

9 13

8 4

0.0

1.9

0.21

0.

01

0.26

2.

69

134

05-J

un-0

1 4.

5 25

0 32

4.

9 1.

2 2.

9 46

0

0.5

0

0.0

0.6

0.09

0.

00

0.15

1.

63

134

19-S

ep-0

1 3.

8 23

2 31

5.

2 0.

9 1.

6 47

0

1.1

2

0.0

0.5

0.04

0.

02

0.13

1.

32

134

30-J

ul-0

2 3.

7 31

4 37

8.

3 2.

3 1.

6 59

0

8.3

119

3 0.

0 1.

1 0.

06

0.01

0.

11

2.66

13

5 05

-Jun

-01

3.4

577

66

9.9

0.6

0.6

124

0 19

.8

2

0.0

1.1

0.03

0.

00

0.28

3.

21

135

19-S

ep-0

1 3.

8 29

5 34

4.

5 0.

6 0.

4 63

0.

9 5.

6 53

7

0.0

1.4

0.02

0.

00

0.24

2.

66

135

30-J

ul-0

2 3.

6 56

8 72

7.

4 0.

6 1.

6 13

5 0

24.3

34

8

0.0

0.8

0.03

0.

02

0.33

5.

95

137

06-M

ay-0

1 4.

0 29

2 37

7.

1 1.

2 0.

3 59

0

2.0

0

0.0

0.6

0.04

0.

00

0.26

2.

22

137

19-S

ep-0

1 4.

0 23

0 34

7.

3 1.

2 1.

0 53

0

0.8

138

3 0.

0 0.

7 0.

03

0.02

0.

23

3.02

13

7 30

-Jul

-02

3.9

381

47

16.6

3.

3 2.

1 89

0

1.2

157

5 0.

0 2.

7 0.

08

0.01

0.

35

3.93

13

8 05

-Jun

-01

3.1

254

30

5.4

1.3

0.9

51

0 1.

0 12

5 1

0.0

1.3

0.03

0.

00

0.21

2.

71

138

30-J

ul-0

2 3.

8 29

5 34

5.

8 1.

6 0.

4 60

0

0.0

154

7 0.

0 1.

6 0.

07

0.01

0.

39

4.16

13

9 05

-Jun

-01

4.4

334

52

10.6

0.

9 0.

5 80

0

2.2

6

0.0

1.4

0.09

0.

00

0.36

2.

21

139

19-S

ep-0

1 4.

3 29

1 36

6.

0 0.

4 0.

6 69

0.

4 0.

8 17

7 9

0.0

0.6

0.03

0.

01

0.32

1.

89

139

30-J

ul-0

2 4.

5 33

2 46

11

.2

0.8

0.4

72

0 1.

7 13

3 10

0.

0 0.

7 0.

09

0.01

0.

46

3.36

14

1 05

-Jun

-01

4.4

97

14

3.6

0.8

0.5

18

1.19

0.

7

10

0.0

0.6

0.03

0.

00

0.12

3.

37

141

19-S

ep-0

1 4.

2 99

11

1.

9 0.

4 2.

9 20

0.

8 0.

4 77

12

0.

0 0.

4 0.

02

0.00

0.

09

2.19

14

1 30

-Jul

-02

4.6

163

20

9.2

2.9

4.4

29

0 2.

0 10

2 16

0.

0 5.

5 0.

20

0.01

0.

17

2.79

14

2 19

-Sep

-01

3.9

71

7 1.

5 0.

8 2.

6 10

0.

5 2.

8

16

0.0

0.4

0.02

0.

02

0.07

0.

24


Wel

l No.

D

ate

pH

Con

d.

Na

Mg

Ca

K

Cl

HC

O3

SO4

DO

C

SiO

2 M

n Fe

Zn

C

u B

r A

l

uS/

cm

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L 14

2 30

-Jul

-02

3.9

102

7 3.

5 3.

8 2.

8 10

0

1.0

100

30

0.0

0.9

0.07

0.

01

0.12

0.

54

145

05-J

un-0

1 3.

5 18

5 15

2.

2 0.

4 0.

6 18

0

0.5

3

0.0

0.3

0.10

0.

00

0.07

1.

57

145

19-S

ep-0

1 3.

6 16

2 15

2.

6 0.

1 1.

2 21

0.

9 3.

9 16

6 4

0.0

0.5

0.03

0.

02

0.09

1.

23

145

30-J

ul-0

2 3.

5 19

8 13

4.

5 0.

2 2.

0 24

0

3.9

5

0.0

0.7

0.12

0.

00

0.10

2.

18

146

05-J

un-0

1 4.

4 69

11

1.

6 1.

6 1.

0 10

1.

71

0.8

5

0.0

0.6

0.04

0.

00

0.05

1.

44

146

19-S

ep-0

1 4.

3 57

31

2.

6 1.

4 0.

4 56

0.

6 1.

8 81

7

0.0

3.2

0.03

0.

01

0.19

2.

60

146

30-J

ul-0

2 4.

4 74

10

1.

9 2.

0 1.

3 12

0

1.4

67

8 0.

0 0.

3 0.

05

0.02

0.

11

4.13

14

9 05

-Jun

-01

3.4

275

29

3.0

1.2

1.8

36

1.24

0.

7

4 0.

0 0.

9 0.

23

0.01

0.

18

0.93

14

9 19

-Sep

-01

3.5

201

18

1.5

0.6

1.3

26

0 0.

7 21

9 4

0.0

0.5

0.03

0.

02

0.10

0.

78

149

30-J

ul-0

2 3.

2 24

9 20

2.

6 1.

1 0.

2 28

0

4.9

228

4 0.

0 1.

2 0.

41

0.00

0.

09

1.15

M

W2S

19

-Sep

-01

4.2

248

53

9.4

4.8

0.3

106

0 11

.2

7

0.1

9.5

0.02

0.

01

0.47

2.

54

MW

3S

26-A

pr-0

0 4.

7 23

9 23

6.

0 2.

0 0.

5 52

0.

5 0.

5

0.

0 2.

7

8.35

M

W3S

17

-Jul

-00

21

4.0

1.0

0.3

40

0.2

4.0

0.0

0.8

1.

44

MW

3S

19-S

ep-0

1 4.

8 17

4 15

3.

6 1.

4 1.

2 44

0.

4 0.

7

6 0.

0 1.

1 0.

09

0.02

0.

17

1.13

M

W4S

26

-Apr

-00

3.7

264

21

4.0

0.5

0.5

43

0.5

3.0

0.0

2.4

8.

55

MW

4S

17-J

ul-0

0

21

4.

0 1.

0 0.

7 34

0.

6 11

.0

0.0

0.9

0.

99

MW

4S

19-S

ep-0

1 3.

6 26

5 31

5.

1 1.

0 1.

5 49

0

5.4

5

0.1

4.0

0.28

0.

19

0.17

1.

40

MW

5S

19-S

ep-0

1 3.

9 38

7 47

11

.0

6.8

0.8

90

0.9

8.1

16

0.

5 15

.3

0.05

0.

01

0.24

5.

36

MW

6S

19-S

ep-0

1 4.

1 10

0 35

6.

1 2.

6 0.

4 63

0.

6 3.

9

10

0.0

3.9

0.02

0.

01

0.22

2.

75

MW

8S

19-S

ep-0

1 3.

9 10

2 9

1.1

0.6

1.2

13

0.8

3.6

19

0.

0 0.

6 0.

02

0.00

0.

04

0.47

Su

rfac

e w

ater

S1

26

-Apr

-00

3.7

194

17

3.0

0.5

0.5

36

0 0.

5

0.

0 1.

0 0.

03

0.00

0.

41

1.70

S1

17

-Jul

-00

30

4.0

1.0

0.5

58

0.5

3.0

0.0

0.6

0.03

0.

00

0.25

1.

18

S1 1

5-N

ov-0

0 3.

4

53

9.5

3.0

0.7

79

0 18

.0

1

0.1

1.2

0.02

0.

00

0.14

0.

76

S2

17-J

ul-0

0 3.

4

47

7.0

0.9

0.7

91

0.5

10.0

0.

0 1.

3 0.

04

0.00

0.

61

2.59

S3

26

-Apr

-00

6.2

2079

37

4 32

.0

9.0

15.0

66

1 16

57

.0

0.0

0.6

0.01

0.

00

0.17

0.

73


Wel

l No.

D

ate

pH

Con

d.

Na

Mg

Ca

K

Cl

HC

O3

SO4

DO

C

SiO

2 M

n Fe

Zn

C

u B

r A

l

uS/

cm

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L S3

22-

May

-00

6.5

46

3 48

.0

16.0

19

.0

814

29

92.0

0.

0 0.

7 0.

02

0.05

0.

26

1.19

S3

20

-Jun

-00

5.6

13

6 15

.0

5.0

5.0

239

3 29

.0

0.0

0.3

0.01

0.

00

0.10

0.

66

S3

17-J

ul-0

0 6.

3

3730

41

8.0

140.

0 15

3.0

6680

24

93

7.0

0.0

0.7

0.01

0.

00

0.10

0.

87

S4

26-A

pr-0

0 4.

0 23

0 20

4.

0 4.

0 0.

5 46

0

3.0

0.0

0.6

0.04

0.

00

0.12

1.

02

S4 2

2-M

ay-0

0 4.

5

23

5.0

5.0

0.5

50

0 9.

0

0.

0 0.

7

0.35

S4

20

-Jun

-00

4.2

24

5.

0 4.

0 0.

5 54

0

7.0

0.0

0.8

0.

67

S4

17-J

ul-0

0 4.

0

40

6.0

4.0

1.0

76

0.5

11.0

0.

0 0.

4 0.

01

0.00

0.

07

0.63

S5

13

-Sep

-00

3.1

213

19

3.0

0.6

0.5

34

0 1.

5

1 0.

0 0.

8 0.

65

0.01

0.

06

0.46

S5

15-

Nov

-00

3.4

21

2.

8 0.

8 1.

3 30

0

3.6

1

0.0

0.4

0.03

0.

00

0.06

0.

24

S5

12-J

ul-0

1

32

5.

4 1.

4 3.

6 52

0

0.4

6

0.0

0.4

0.04

0.

00

0.06

0.

27

S6

13-S

ep-0

0 3.

1 17

6 16

2.

7 0.

5 0.

8 21

0

2.2

2

0.1

0.5

0.19

0.

00

0.06

0.

70

S6 1

5-N

ov-0

0 3.

2

17

2.6

0.9

0.8

26

0 4.

5

1 0.

0 0.

4 0.

02

0.00

0.

08

0.42

S9

14

-Sep

-00

7 44

400

4390

52

9 16

3 15

9 16

806

70

2274

.0

91

0.0

0.3

0.04

0.

00

0.11

0.

80

S10

13-S

ep-0

0 3.

6 87

11

2.

2 1.

4 1.

3 11

0

1.7

16

0.

0 0.

3 0.

02

0.00

0.

20

0.24

S1

0 15

-Nov

-00

3.5

11

2.

8 1.

9 1.

2 15

0

1.5

0

0.0

0.3

0.01

0.

00

0.08

0.

22

S10

12-J

ul-0

1

12

3.

4 2.

0 1.

2 30

0

0.4

0

0.0

0.5

0.08

0.

00

0.08

0.

78

S11

13-S

ep-0

0 3.

3 19

8 21

2.

2 0.

8 1.

0 24

0

1.7

2

0.0

0.3

0.01

0.

00

0.06

0.

61

S11

15-N

ov-0

0 3.

4

21

2.3

0.9

1.1

27

0 3.

9

2 0.

0 0.

5 0.

03

0.00

0.

16

0.93

S1

1 12

-Jul

-01

21

2.0

0.8

0.5

31

0 1.

9

3 0.

0 0.

2 0.

06

0.00

0.

14

0.56

S1

2 14

-Sep

-00

4.3

194

31

3.3

0.8

0.9

54

0 3.

2

4 0.

0 0.

4 0.

13

0.00

0.

11

0.63

S1

2 15

-Nov

-00

5.5

17

1.

9 1.

1 1.

8 22

2.

32

7.0

2

0.0

0.5

0.00

0.

00

0.09

0.

29

S13

14-S

ep-0

0 3.

7 16

2 12

2.

2 0.

6 0.

8 21

0

1.8

2

0.1

0.6

0.15

0.

01

0.13

1.

49

S13

15-N

ov-0

0 3.

5

15

2.5

0.5

0.5

26

0 2.

4

1 0.

0 1.

5 0.

01

0.00

0.

17

1.42

S1

4 14

-Sep

-00

2.9

291

51

7.5

3.9

1.6

44

0 0.

7

0 0.

0 0.

4 0.

01

0.00

0.

20

1.61

S1

4 15

-Nov

-00

3.2

32

5.

4 1.

6

46

0 18

.0

1

0.6

0.6

0.13

0.

01

0.14

1.

25

S15

14-S

ep-0

0 3.

3 25

4 31

6.

2 4.

8 1.

1 45

0

3.2

2

0.0

0.8

0.03

0.

00

0.18

1.

25


Wel

l No.

D

ate

pH

Con

d.

Na

Mg

Ca

K

Cl

HC

O3

SO4

DO

C

SiO

2 M

n Fe

Zn

C

u B

r A

l

uS/

cm

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L S1

5 15

-Nov

-00

3.5

34

6.

9 1.

5 0.

8 52

0

8.8

3

0.0

0.7

0.05

0.

00

0.24

1.

55

S15

12-J

ul-0

1

35

6.

5 1.

2 0.

3 59

0

5.6

0

0.0

1.4

0.02

0.

00

0.30

0.

77

S16

14-S

ep-0

0 2.

3 30

2 35

7.

8 68

.0

1.1

61

0 6.

3

1 0.

0 4.

5 0.

01

0.01

0.

30

0.98

S1

6 15

-Nov

-00

3.4

45

6.

5 2.

0 1.

1 66

0

8.7

1

0.0

0.3

0.01

0.

00

0.06

0.

46

S16

12-J

ul-0

1

57

8.

0 1.

9 4.

2 79

0

10.4

1 0.

0 0.

5 0.

00

0.00

0.

07

0.24

S1

7 14

-Sep

-00

3.5

516

60

13.2

5.

5 1.

4 11

6 0

44.3

11

0.0

0.4

0.01

0.

00

0.08

0.

55

S17

15-N

ov-0

0 3.

5

61

11.8

5.

1 1.

2 11

7 0

45.5

9 0.

0 0.

2 0.

09

0.00

0.

09

0.81

S1

8 14

-Sep

-00

3.5

101

12

2.1

2.0

0.9

17

0 1.

1

6 0.

0 0.

6

1.06

S1

8 15

-Nov

-00

3.8

18

2.

0 1.

6 1.

2 21

0

4.5

2

0.0

0.5

0.03

0.

00

0.09

0.

58

S19

15-N

ov-0

0 3.

7

17

3.0

2.5

1.1

24

0 4.

0

1 0.

0 0.

4 0.

10

0.00

0.

06

0.59

S1

9 12

-Jul

-01

15

2.6

2.2

0.0

25

0 5.

6

1 0.

0 0.

2 0.

02

0.00

0.

03

0.54

S2

0 15

-Nov

-00

3.3

11

2.

1 1.

0 1.

3 15

0

3.4

4

0.0

2.2

0.

35

S20

12-J

ul-0

1

10

2.

3 1.

1 1.

8 20

0

3.6

5

0.0

2.2

0.

58

S22

15-N

ov-0

0 4.

0

10

2.3

3.8

1.4

10

0 7.

0

5 0.

0 0.

7

0.19

S2

3 12

-Jul

-01

20

2.7

0.4

2.7

28

0 1.

1

4 0.

1 0.

2

0.29

S2

4 12

-Jul

-01

42

6.3

1.5

1.2

66

0 1.

8

0 0.

1 2.

2

1.15

S2

5 12

-Jul

-01

45

8.1

3.2

2.3

81

0 1.

3

2 0.

1 2.

9

1.36

S2

6 12

-Jul

-01

85

14.6

2.

7 5.

7 11

3 0

6.3

17

0.

1 1.

7

1.20

S2

7 12

-Jul

-01

52

8.3

2.5

3.0

79

0 0.

4

1 0.

1 2.

4

2.85

S2

8 12

-Jul

-01

78

11.1

2.

5 2.

9 11

3 0

5.1

1

0.0

0.7

0.07

0.

00

0.06

0.

83

S29

12-J

ul-0

1

42

5.

8 1.

6 4.

0 67

0

2.8

5

0.0

0.5

0.01

0.

00

0.07

0.

50

S30

12-J

ul-0

1

16

3.

0 0.

3 1.

1 30

0

2.7

3

0.0

1.1

0.02

0.

00

0.20

1.

17

S31

12-J

ul-0

1

29

2.

9 1.

1 0.

1 46

0

3.8

0

0.0

0.5

1.69

0.

00

0.08

0.

53

S32

12-J

ul-0

1

34

5.

3 1.

1 3.

8 53

0

3.0

1

0.0

0.7

0.03

0.

00

0.09

0.

36

S33

12-J

ul-0

1

1

3.9

1.1

3.4

51

0 6.

0

1 0.

0 0.

1 0.

09

0.23

56

.00

3.98


Wel

l No.

D

ate

pH

Con

d.

Na

Mg

Ca

K

Cl

HC

O3

SO4

DO

C

SiO

2 M

n Fe

Zn

C

u B

r A

l

uS/

cm

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L m

g/L

mg/

L se

awat

er

10

500

1350

.040

0.0

380.

0 19

000

142

2700

.0

6

0.0

65.0

0

seaw

ater

8.2

10

060

1300

.044

5.0

395.

0 21

00

150

2180

.0

5

lo

cal r

ain

18-F

eb-9

7 5.

7 22

2

0.4

0.9

0.1

3 >

.1

> .1

1

lo

cal r

ain

18-F

eb-9

7 5.

6 7

0 0.

1 0.

2 0.

0 1

> .1

>

.1

>

1

lo

cal r

ain

18-F

eb-9

7 7.

4 20

0

0.1

0.1

0.0

2 >

.1

> .1

> 1

loca

l rai

n 18

-Feb

-97

6.3

55

3 0.

5 7.

0 0.

2 4

2.7

> .1

7

lo

cal r

ain

18-F

eb-9

7 5.

9 35

3

0.7

2.8

0.6

5 0.

6 >

.1

1

loca

l rai

n 14

-Oct

-00

4.3

3

0.4

0.5

0.1

3 0

1.3

0.0

0.0

0.11

0.01

0.

31


Appendix I

Calculation of Organic Anion Concentration

Appendix I – calculation of organic anion concentration

Calculation of Anion Contribution from Dissolved organic matter:

[A-] = concentration of Anions contributed by dissolved organic matter. In eq/l

ie. Ionised carboxyl groups

[A-] = K [CT] K + [H+]

Where [CT] = organic (fluvic + humic acid concentrations in eq/L ie. Total carboxyl groups

K = mass action quotient Calculation of K

pK = 0.96 + 0.90pH - 0.09(pH)2 Where pK = negative log of K (-logK)

... K = 10-(0.96 + 0.90pH - 0.09(pH)2 eq/L Calculation of [CT] A carboxyl content of 10 eq/mg organic carbon is assumed (Oliver et al, 1983)

[CT] = [Dissolved mg/L organic carbon] x 10 µeq/mg = ….µeq/L eg. Sample: S18

pH: 3.79 [H+] = 1.622 x 10-4

[H+] = -logpH

TOC: 99.45 mg/L [CT] = 9.9945 x 10-4

Calc of K

pK = 0.96 + 0.90 x 3.79 - 0.039 (3.79) 4.371 - 0.5602

pK = 3.81 K = 1.549 x 10-4

Calc of [A-]

[A-] = k [CT] K + [H+] = (1.549 x 10-4) x 9.945 x 10-4 1.549 x 10-4 + 1.622 x 10-4 = 1.540 x 10-7 3.171 x 10-4 = 4.86 x 10-4 eq/L = 0.486 meq/L

Cation = 1.0995 Anion = 0.7203 + 0.486 = 1.206

Balance = -4.60%


Sample 140 141 132 146 133 88 pH 5.3 4.6 3.7 4.4 3.4 6 TOC mg/L 22.31 102.3 134.7 67.25 138.1 41.93 Cation total meq/L 2.85 2.11 2.36 0.76 2.8 3.46 Anion total meq/L 2.65 0.92 1.72 0.39 2.5 2.54 [H+] mg/L 5E-06 2.5E-05 0.0002 4E-05 0.0004 1E-06 Ct eq/L 0.00022 0.00102 0.00135 0.00067 0.00138 0.00042 pK 4.63 4.27 3.76 4.16 3.57 4.96 K eq/L 2.3E-05 5.3E-05 0.00018 6.8E-05 0.00027 1.1E-05 [A-] eq/L 0.00018 0.00069 0.00063 0.00043 0.00056 0.00038 =K[Ct]/(K+[H+]) [A-] meq/L 0.1835 0.6946 0.6301 0.4251 0.5577 0.3846 Old Ion balance % -3.5 39.3 14.9 31.9 5.7 15.3 New Ion Balance % 0.3 13.3 0.2 -3.5 -4.4 8.4 Sample 139 145 136 101 149 100 pH 4.5 3.5 5 4.7 3.2 5 TOC mg/L 132.9 2.473 26.47 40.47 227.8 0.8411 Cation total meq/L 3.01 1.04 2.54 1.62 1.19 2.82 Anion total meq/L 2.09 0.88 2.37 1.3 0.91 3.35 [H+] mg/L 3.2E-05 0.00032 0.00001 2E-05 0.00063 0.00001 Ct eq/L 0.00133 2.5E-05 0.00026 0.0004 0.00228 8.4E-06 pK 4.22 3.63 4.49 4.33 3.44 4.49 K eq/L 6E-05 0.00023 3.3E-05 4.7E-05 0.00036 3.3E-05 [A-] eq/L 0.00087 1E-05 0.0002 0.00028 0.00083 6.4E-06 =K[Ct]/(K+[H+]) [A-] meq/L 0.8714 0.0105 0.2028 0.2840 0.8313 0.0064 Old Ion balance % 18.0 8.5 3.4 11.0 12.9 -8.5 New Ion Balance % 0.8 7.7 -0.6 1.1 -18.8 -8.7


Sample 144 89 150 142 151 143 pH 5.4 5 3.5 3.9 4.4 3.9 TOC mg/L 37.65 22.26 171.2 99.99 83.94 90.72 Cation total meq/L 11 3.6 1.74 0.87 1.93 0.87 Anion total meq/L 17.59 2.74 1.34 0.36 1.84 0.58 [H+] mg/L 4E-06 0.00001 0.00032 0.00013 4E-05 0.00013 Ct eq/L 0.00038 0.00022 0.00171 0.001 0.00084 0.00091 pK 4.68 4.49 3.63 3.88 4.16 3.88 K eq/L 2.1E-05 3.3E-05 0.00023 0.00013 6.8E-05 0.00013 [A-] eq/L 0.00032 0.00017 0.00073 0.00051 0.00053 0.00047 =K[Ct]/(K+[H+]) [A-] meq/L 0.3159 0.1705 0.7267 0.5133 0.5306 0.4657 Old Ion balance % -23.0 13.5 13.1 41.4 3.7 20.3 New Ion Balance % -23.9 10.6 -8.6 -0.2 -10.2 -9.2 Sample 134 131 148 147 138 126 pH 3.7 4.2 4.6 4.8 3.8 4.4 TOC mg/L 118.9 58.67 29.01 33.02 153.8 103.9 Cation total meq/L 2.47 0.74 0.65 0.79 2.12 0.97 Anion total meq/L 1.84 0.35 0.91 0.76 1.7 0.4 [H+] mg/L 0.0002 6.3E-05 2.5E-05 1.6E-05 0.00016 4E-05 Ct eq/L 0.00119 0.00059 0.00029 0.00033 0.00154 0.00104 pK 3.76 4.05 4.27 4.38 3.82 4.16 K eq/L 0.00018 8.9E-05 5.3E-05 4.2E-05 0.00015 6.8E-05 [A-] eq/L 0.00056 0.00034 0.0002 0.00024 0.00075 0.00066 =K[Ct]/(K+[H+]) [A-] meq/L 0.5562 0.3428 0.1970 0.2390 0.7541 0.6567 Old Ion balance % 14.7 35.8 -17.0 1.6 10.9 41.6 New Ion Balance % 1.5 3.3 -26.0 -11.7 -7.3 -4.3


Sample 115 129 137 115 121 123 pH 3.4 4.4 3.9 3.34 5.01 3.9 TOC mg/L 83.92 55.22 157.1 113.1 18.23 100.9 Cation total meq/L 1.98 1.13 3.74 2.3712 2.2995 1.1235 Anion total meq/L 1.88 0.57 2.54 2.2833 1.9075 0.9314 [H+] mg/L 0.0004 4E-05 0.00013 0.00046 9.8E-06 0.00013 Ct eq/L 0.00084 0.00055 0.00157 0.00113 0.00018 0.00101 pK 3.57 4.16 3.88 3.53 4.49 3.88 K eq/L 0.00027 6.8E-05 0.00013 0.00029 3.2E-05 0.00013 [A-] eq/L 0.00034 0.00035 0.00081 0.00044 0.00014 0.00052 =K[Ct]/(K+[H+]) [A-] meq/L 0.3389 0.3490 0.8065 0.4432 0.1400 0.5180 Old Ion balance % 2.5 33.1 19.2 1.89 9.32 21.14 New Ion Balance % -5.7 10.3 5.6 -6.969 5.797 -12.665 Sample 126 S5 S6 S11 S12 S13 pH 4.75 3.4 3.2 3.36 5.49 3.46 TOC mg/L 80.97 80.03 127.2 144 20.05 105.6 Cation total meq/L 1.0981 1.2404 1.0815 1.2112 1.0259 0.9436 Anion total meq/L 0.468 0.9731 0.8886 0.8587 0.8127 0.8224 [H+] mg/L 1.8E-05 0.0004 0.00063 0.00044 3.2E-06 0.00035 Ct eq/L 0.00081 0.0008 0.00127 0.00144 0.0002 0.00106 pK 4.36 3.57 3.44 3.54 4.73 3.61 K eq/L 4.4E-05 0.00027 0.00036 0.00029 1.9E-05 0.00025 [A-] eq/L 0.00058 0.00032 0.00046 0.00057 0.00017 0.00044 =K[Ct]/(K+[H+]) [A-] meq/L 0.5772 0.3232 0.4642 0.5700 0.1711 0.4394 Old Ion balance % 40.23 12.08 9.79 17.03 11.6 6.86 New Ion Balance % 2.468 -2.203 -11.144 -8.237 2.096 -14.429


Sample S15 S16 S17 S18 S20 S22 pH 3.5 3.41 3.52 3.79 3.34 4.03 TOC mg/L 133 142.1 20.02 114.1 92.38 65.3 Cation total meq/L 2.2763 2.7161 4.2104 1.0995 0.783 0.9017 Anion total meq/L 1.6695 2.063 4.2537 0.7203 0.5783 0.4484 [H+] mg/L 0.00032 0.00039 0.0003 0.00016 0.00046 9.3E-05 Ct eq/L 0.00133 0.00142 0.0002 0.00114 0.00092 0.00065 pK 3.63 3.58 3.64 3.81 3.53 3.95 K eq/L 0.00023 0.00027 0.00023 0.00015 0.00029 0.00011 [A-] eq/L 0.00056 0.00058 8.6E-05 0.00056 0.00036 0.00036 =K[Ct]/(K+[H+]) [A-] meq/L 0.5645 0.5767 0.0858 0.5568 0.3620 0.3551 Old Ion balance % 15.38 13.67 -0.51 20.84 15.04 33.57 New Ion Balance % 0.937 1.426 -1.510 -7.474 -9.126 5.756

determination of aquifer properties and...

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