tatiara pwa: groundwater resource condition and modelling results · 2017. 9. 4. · tatiara pwa:...

Tatiara PWA: Groundwater Resource Condition and Modelling Results• Overview of resource and condition• Potential resource condition limits• Groundwater modelling• ResultsCommunity Meeting in Keith – 31/8/2017

Roger CranswickSenior HydrogeologistWater Science Unit

Hydrogeology and Hydrogeological Zones• Two broad regions, coastal

plain and mallee highlands

• Unconfined aquifers found within different types of limestones that store and transmit groundwater

• Groundwater recharge is sourced from rainfall and runaway holes

• Unconfined extraction ranges from 60–112 GL/y

• Full allocation 139 GL/y

• Confined aquifer extraction is small, < 400 ML/y

Hydrogeological Cross-Section

Coomandook Formation

Coastal Plain

Padthaway Formation

Basement

Qua

tern

ary

Lim

esto

ne A

quife

r

Murray Group Limestone

Mallee Highlands

Loxton-Parilla Sands

Ettrick Marl

Murray G

roup Limestone Aquifer


Bridgewater Formation

Highland Transition

Not to scale

Watertable

A A’

Quaternary limestone aquifer• Thin (< 30 to 40 m) with very high

yields in upper section• Higher groundwater salinity• Rainfall and irrigation recharge• Throughflow from highlands• ~71 GL/y groundwater extracted

Murray Group Limestone aquifer• Thick (up to 90 m) with moderate yields• Lower groundwater salinity• Rainfall recharge and throughflow• ~15 GL/y groundwater extracted

Coastal PlainQuaternary Limestone Aquifer

Mallee HighlandsTertiary Limestone Aquifer


Coastal Plain

Padthaway Formation

Basement

Qua

tern

ary

Lim

esto

ne A

quife

r


Mallee Highlands


Ettrick Marl

Murray G




Highland Transition

Not to scale

Watertable

A A’

Average Groundwater Balance (1985)

101 GL/y74 GL/y

10 GL/y

0 GL/y

Murray Group Limestone aquifer• Moderate inflows (53 GL/y)• Moderate outflows (53 GL/y)• No loss of storage (0 GL/y)

Quaternary limestone aquifer• Large inflows (137 GL/y)• Large outflows (137 GL/y)• No storage loss (0 GL/y)

34 GL/y

8 GL/y

0 GL/y




Coastal Plain

Padthaway Formation

Basement

Qua

tern

ary

Lim

esto

ne A

quife

r


Mallee Highlands


Ettrick Marl

Murray G




Highland Transition

Not to scale

Watertable

A A’

Average Groundwater Balance (2006-2015)

38 GL/y71 GL/y

1 GL/y

20 GL/y

Murray Group Limestone aquifer• Moderate inflows (36 GL/y)• Moderate outflows (66 GL/y)• Considerable loss of storage

(30 GL/y) – from western margin• Very small % reduction of total

storage in the MGL aquifer

Quaternary limestone aquifer• Large inflows (83 GL/y)• Large outflows (103 GL/y)• Considerable storage loss (20 GL/y)• Possible implications for aquifer

performance

14 GL/y

15 GL/y

30 GL/y



Regional Groundwater Flow• Regional groundwater flow

approximately east to west

• Depth to groundwater is 40 to 65 m in the east and approximately

Groundwater Level Trends

505254565860

1970 1980 1990 2000 2010 2020

RWSL

(mAH

D)

Year

SHG007

60

62

64

66

68

70

1970 1980 1990 2000 2010 2020

RWSL

(mAH

D)

Year

SEN01445

47

49

51

53

55

1970 1980 1990 2000 2010 2020

RWSL

(mAH

D)

Year

CAN012

40

42

44

46

48

50

1970 1980 1990 2000 2010 2020

RWSL

(mAH

D)

Year

PET015

252729313335

1970 1980 1990 2000 2010 2020

RWSL

(mAH

D)

Year

WLL020

20

22

24

26

28

30

1970 1980 1990 2000 2010 2020

RWSL

(mAH

D)

Year

STR017

22

24

26

28

30

32

1970 1980 1990 2000 2010 2020

RWSL

(mAH

D)

Year

WLL108

60

62

64

66

68

70

1970 1980 1990 2000 2010 2020

RWSL

(mAH

D)

Year

TAT010

45

47

49

51

53

55

1970 1980 1990 2000 2010 2020

RWSL

(mAH

D)Year

WRG011

• Stable trends in highlands

• Stable to declining trends on the coastal plain

Groundwater Resources: Salinity All Data• Groundwater salinity

increases from east to west

• Salinity influenced by• Recharge processes• Shallow watertables• Land clearance• Irrigation recycling

GDE

Groundwater Salinity Trends

0

1000

2000

3000

1975 1985 1995 2005 2015

Salin

ity (m

g/L)

Year

SHG004

0

1000

2000

3000

1975 1985 1995 2005 2015

Salin

ity (m

g/L)

Year

TAT108

1000

2000

3000

4000

1975 1985 1995 2005 2015

Salin

ity (m

g/L)

Year

WLL104

1000

2000

3000

4000

1975 1985 1995 2005 2015

Salin

ity (m

g/L)

Year

WRG116

3000

4000

5000

6000

1975 1985 1995 2005 2015

Salin

ity (m

g/L)

Year

STR111

2000

3000

4000

5000

1975 1985 1995 2005 2015

Salin

ity (m

g/L)

Year

PET104

1000

2000

3000

4000

1975 1985 1995 2005 2015

Salin

ity (m

g/L)

Year

CAN104

0

1000

2000

3000

1975 1985 1995 2005 2015

Salin

ity (m

g/L)

Year

SEN018

2000

3000

4000

5000

1975 1985 1995 2005 2015Sa

linity

(mg/

L)Year

WRG114

• Stable trends in east• Changing trends after

land clearance• Rising trends on the

coastal plain

Evolution of management approachesTraditional Approach• Allocations guided by estimates of average recharge but…

– These estimates contain uncertainty (sometimes +/- 50%)– Recharge varies widely across the landscape and over time (wet and dry periods)– Irrigation responsive to rainfall (Tatiara PWA extraction has ranged from 60–112 GL/y)– What to do with unexpected changes (large areas of declining WLs, increasing salinity)?

Resource Condition Limit Approach• Approach aims to keep the condition of the resource within agreed limits,

to avoid unacceptable levels of risk to the economic, social or environmental values associated with the groundwater resource

• Should be specific to the local or regional behaviour of the aquifer (e.g. could be applied to hydrogeological zones)

• Should be measurable to enable management responses based on changing resource condition (i.e. resource condition triggers)

• To be developed through engagement with community and stakeholders• RCLs presented shown here are examples of possible RCLs

Possible Resource Condition Limits (RCLs)Coastal Plain• Aquifer Performance (yield) – maintain

water levels in high yielding parts of aquifer

• Hydraulic Gradient – maintain throughflow to prevent rapidly increasing salinity and reversal of regional flow

Mallee Highlands• Hydraulic Gradient – maintain

throughflow to mitigate increasing salinity and deliver groundwater to the coastal plain

What will happen to each RCL• if extraction increases/decreases?• and/or if recharge decreases?• Can resource condition triggers be

effective in preventing RCL exceedance?

14

16

18

20

22

24

26

1985 1995 2005 2015

Wat

erle

vel (

mA

HD

)

Aquifer Performance (Coastal Plain)

STR111 STR111 RCL Pad Fmn Base

14

16

18

20

22

24

26

1985 1995 2005 2015

Wat

erle

vel (

mA

HD

)

Hydraulic Gradient (Coastal Plain)STR110 LAF003

50

55

60

65

70

1985 1995 2005 2015

Wat

erle

vel (

mA

HD

)

Hydraulic Gradient (Highlands)

TAT108 WRG116

0

1000

2000

3000

4000

5000

6000

7000

8000

1985 1990 1995 2000 2005 2010 2015 2020 2025 2030

Grou

ndw

ater

Sal

inity

(mg/

L)

STR111 STR111 Linear (STR111)

Salinity Trajectory• Rising salinity trends caused by irrigation recycling likely to continue if local

groundwater is used for irrigation

• Trajectory of trends towards specific crop thresholds may be a useful indicator

• For example:• ~1500 mg/L for grapes and potatoes• ~3000 mg/L for spray irrigation of lucerne• ~7000 mg/L for flood irrigation of lucerne

0

1000

2000

3000

4000

5000

6000

7000

8000

1985 1990 1995 2000 2005 2010 2015 2020 2025 2030

Grou

ndw

ater

Sal

inity

(mg/

L)

STR111 STR111 Salinity Threshold Linear (STR111)

Approx 12 years until threshold reached

Key Messages – Resource Condition• Coastal plain had steady WLs from the mid-1970s to mid-

1990s before a considerable declines

• Mallee highlands have steady WLs with some declining trends adjacent to the coastal plain

• Consistent rising salinity in some parts of the coastal plain due to irrigation recycling

• Influence of clearing native vegetation is yet to be observed in most of the mallee highlands but has shown changes where depth to watertable is shallow (~< 15 m)

• Resource condition limits to be specific, measureable and developed through engagement with stakeholders/community

• RCLs give context to previous analysis of trends, e.g. “triggers”– Coastal plain: aquifer performance (yields) and hydraulic gradient

– Mallee highlands: hydraulic gradient

Questions

Groundwater Resource Condition

Tatiara Groundwater Model • 97 km N–S, 84 km E–W • Broken up into 200x200 m

cells and 2 layersObservation wells

Extraction dataHydraulic parameter zones

Recharge inputs

• Model simulates groundwater flow and groundwater level variations

• Does not directly simulate salinity dynamics but…• Can be used to assess the risk of changing salinity

based on groundwater flow (rates and direction)

Mallee highlands

Coastal plain

Tatiara Groundwater Model: Calibration

15

17

19

21

23

25

1985 1995 2005 2015

Head

(m A

HD)

STR2

Observed Model A

Model B Model C

20

22

24

26

28

30

1985 1995 2005 2015

Head

(m A

HD)

STR116

Observed Model A

Model B Model C

55

57

59

61

63

65

1985 1995 2005 2015

Head

(m A

HD)

SHG7

Observed Model A

Model B Model C

50

52

54

56

58

60

1985 1995 2005 2015

Head

(m A

HD)

WRG116

Observed Model A

Model B Model C

45

47

49

51

53

55

1985 1995 2005 2015

Head

(m A

HD)

WRG11

Observed Model A

Model B Model C

20

22

24

26

28

30

1985 1995 2005 2015

Head

(m A

HD)

WLL106

Observed Model A

Model B Model C

70

72

74

76

78

80

1985 1995 2005 2015

Head

(m A

HD)

TAT106

Observed Model A

Model B Model C

65

67

69

71

73

75

1985 1995 2005 2015

Head

(m A

HD)

SEN6

Observed Model A

Model B Model C

45

47

49

51

53

55

1985 1995 2005 2015

Head

(m A

HD)

PET104

Observed Model A

Model B Model C

• High to medium confidence for 82% of observation wells

• Some uncertainty where aquifer is thin and highly variable in nature

Tatiara Groundwater Model: Mass balance• Rainfall recharge lower after mid to late-1990s• Extraction relatively consistent but is variable from year to year• Storage decreasing since the mid-1990s• Regional outflow decreasing as water levels decline

-150

-100

-50

0

50

100

150

200

250

1985 1990 1995 2000 2005 2010 2015

Flux

(G

L/y)

Tatiara PWA Groundwater Balance Diffuse rechargeExtractionStoragePoint rechargeGroundwater ETInflowOutflowDiffuse Recharge

InflowPoint Recharge

Groundwater ET

Extraction

OutflowStorage

Future Scenarios

• Four extraction scenarios• S1 – Extraction at full allocation (130 GL)• S2 – Periodic high/low (102, 82, 61 GL… = 93 GL)• S3 – Current extraction (84 GL)• S4 – Lower extraction (61 GL)

• SA Climate Ready datasets produced by Goyder Institute• Best available projections of weather data for SA• We included wet, dry and average projected rainfall datasets

• Used Upper South East recharge model: compared to the 1986–2005 average, 2016–2045 average:• Rainfall is 5 to 8 % lower• Temperatures 0.8 to 1.4 OC warmer• Recharge lower by 12 to 19 %

but still higher than 2006–20150

50

100

150

0

50

100

150

Rech

arge

(G

L/y)

Intermediate

Carbon Emission Scenario

1986-19951996-20052006-20152016-20252026-20352036-2045

High Carbon Emission Scenario

Questions

Groundwater Model Development

15

17

19

21

23

25

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

STR2

Observed S1I S1H

40

42

44

46

48

50

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

PET104

Observed S1I S1H

50

52

54

56

58

60

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

SHG7

Observed S1I S1H

15

17

19

21

23

25

27

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

STR116

Observed S1I S1H

45

47

49

51

53

55

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

WRG11

Observed S1I S1H

60

62

64

66

68

70

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

SEN4

Observed S1I S1H

15

17

19

21

23

25

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

WLL106

Observed S1I S1H

45

47

49

51

53

55

57

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

WRG116

Observed S1I S1H

65

67

69

71

73

75

1985 1995 2005 2015 2025 2035 2045He

ad (m

AHD

)

TAT20

Observed S1I S1H

S1 – Full Allocation

Hydrograph Projections

50

52

54

56

58

60

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

WRG116

Observed S2I S2H

45

47

49

51

53

55

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

WRG11

Observed S2I S2H

20

22

24

26

28

30

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

WLL106

Observed S2I S2H

65

67

69

71

73

75

1985 1995 2005 2015 2025 2035 2045He

ad (m

AHD

)

TAT20

Observed S2I S2H

15

17

19

21

23

25

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

STR2

Observed S2I S2H

20

22

24

26

28

30

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

STR116

Observed S2I S2H

50

52

54

56

58

60

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

SHG7

Observed S2I S2H

60

62

64

66

68

70

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

SEN4

Observed S2I S2H

40

42

44

46

48

50

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

PET104

Observed S2I S2H

S2 – Periodic Extraction


45

47

49

51

53

55

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

WRG11

Observed S3I S3H

50

52

54

56

58

60

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

WRG116

Observed S3I S3H

20

22

24

26

28

30

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

WLL106

Observed S3I S3H

65

67

69

71

73

75

1985 1995 2005 2015 2025 2035 2045He

ad (m

AHD

)

TAT20

Observed S3I S3H

15

17

19

21

23

25

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

STR2

Observed S3I S3H

20

22

24

26

28

30

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

STR116

Observed S3I S3H

50

52

54

56

58

60

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

SHG7

Observed S3I S3H

60

62

64

66

68

70

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

SEN4

Observed S3I S3H

40

42

44

46

48

50

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

PET104

Observed S3I S3H

S3 – Average Extraction


45

47

49

51

53

55

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

WRG11

Observed S4I S4H

50

52

54

56

58

60

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

WRG116

Observed S4I S4H

20

22

24

26

28

30

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

WLL106

Observed S4I S4H

65

67

69

71

73

75

1985 1995 2005 2015 2025 2035 2045He

ad (m

AHD

)

TAT20

Observed S4I S4H

15

17

19

21

23

25

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

STR2

Observed S4I S4H

20

22

24

26

28

30

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

STR116

Observed S4I S4H

50

52

54

56

58

60

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

SHG7

Observed S4I S4H

60

62

64

66

68

70

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

SEN4

Observed S4I S4H

40

42

44

46

48

50

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

PET104

Observed S4I S4H

S4 – Lower Extraction


From 1995 to 2015

Indicative change in waterlevels, 1995–2015

S1 – Extraction at Full Allocation


S2 – Periodic Extraction


S3 – Average Extraction


S4 – Lower Extraction


-150

-100

-50

0

50

100

150

Diffuserecharge

Lateralinflow

Pointrecharge

ET Storage Lateraloutflow

Extraction

10-y

ear a

vera

ge ra

te (G

L/y)

S1H (Tatiara PWA) 1986-19951996-20052006-20152016-20252026-20352036-2045

Implications for storage and outflow• Loss of storage continues overall – performance of aquifers and waterlevels• Lateral outflow increases with decreasing extraction – influences salinity trends

-150

-100

-50

0

50

100

150

Diffuserecharge

Lateralinflow

Pointrecharge


Extraction

10-y

ear a

vera

ge ra

te (G

L/y)

S2H (Tatiara PWA) 1986-19951996-20052006-20152016-20252026-20352036-2045


-150

-100

-50

0

50

100

150

Diffuserecharge

Lateralinflow

Pointrecharge


Extraction

10-y

ear a

vera

ge ra

te (G

L/y)

S3H (Tatiara PWA) 1986-19951996-20052006-20152016-20252026-20352036-2045


-150

-100

-50

0

50

100

150

Diffuserecharge

Lateralinflow

Pointrecharge


Extraction

10-y

ear a

vera

ge ra

te (G

L/y)

S4H (Tatiara PWA) 1986-19951996-20052006-20152016-20252026-20352036-2045


13

15

17

19

21

23

25

15

17

19

21

23

25

27

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)

S1: Aquifer Performance RCL

S1I S1H Observed RCL (3 m) Base PFm

Implications for resource condition limits• a specific and measurable condition which reflects an unacceptable risk to the

groundwater resource and stakeholders/community• E.g. aquifer performance (yield): maintain WLs within high yielding part of aquifer

RCL likely to be exceeded

13

15

17

19

21

23

25

15

17

19

21

23

25

27

1985 1995 2005 2015 2025 2035 2045

Head

(m A

HD)





Questions

Development of Resource Condition Limits

Model Results

Key Messages – Model Overview• Groundwater trends and levels are well simulated by the Model with high

to medium confidence in all areas

• Projected recharge is 12–19 % lower than 1986–2005 average but– This is still higher than more recent 2006–2015 average

– Relative increases to recharge help stabilise coastal plain WLs in some scenarios

• Continued declines projected for the mallee highlands – Mostly next to the coastal plain

– Due to the influence of ~20 years of declining WLs on coastal plain

• Throughflow to the west– Full allocation extraction shows decreasing of outflows, this increases risk of worsening

salinity trends

– Lower/Average/Periodic extraction shows similar or greater outflow rates than 2006–2015

• RCLs are generally not exceeded*– *Except funder full allocation extraction which shows continuing WL declines

– *As long as the rainfall recharge picks up (relative to the recent particularly dry period)

Key Messages – Scenarios and Risk• Full allocation extraction (S1 – 130 GL/y)

– Declining WLs on coastal plain (2-5 m) with declines in highlands (2-3 m), mostly adjacent to plains

– Coastal plain RCLs are likely to be exceeded

– Increased risk of both enhanced salinity trends and reduction in aquifer performance (yield)

• Periodic extraction (S2 – 93 GL/y)– Stable to declining WLs on coastal plain (

Implications for the revision of the WAP• Resource condition limits to be further developed and agreed upon

– should be specific and measurable in each hydrogeological zone

• Model results can be applied to inform: – risk of reaching agreed RCLs of different extraction rates

– effectiveness of management approaches

• Further scenarios can run to test policy settings

Questions

Groundwater Model Projections

Tatiara PWA: Groundwater Resource Condition and Modelling ResultsHydrogeology and Hydrogeological ZonesHydrogeological Cross-SectionAverage Groundwater Balance (1985)Average Groundwater Balance (2006-2015)Regional Groundwater FlowGroundwater Level TrendsGroundwater Resources: Salinity All DataGroundwater Salinity TrendsEvolution of management approachesPossible Resource Condition Limits (RCLs)Salinity TrajectoryKey Messages – Resource ConditionQuestions ��Groundwater Resource ConditionTatiara Groundwater ModelTatiara Groundwater Model: CalibrationTatiara Groundwater Model: Mass balanceFuture ScenariosQuestions ��Groundwater Model DevelopmentHydrograph ProjectionsHydrograph ProjectionsHydrograph ProjectionsHydrograph ProjectionsIndicative change in waterlevels, 1995–2015Indicative change in waterlevels, 2015–2045Indicative change in waterlevels, 2015–2045Indicative change in waterlevels, 2015–2045Indicative change in waterlevels, 2015–2045Implications for storage and outflowImplications for storage and outflowImplications for storage and outflowImplications for storage and outflowImplications for resource condition limitsImplications for resource condition limitsImplications for resource condition limitsImplications for resource condition limitsQuestions ��Development of Resource Condition Limits��Model ResultsKey Messages – Model OverviewKey Messages – Scenarios and RiskImplications for the revision of the WAPQuestions ��Groundwater Model ProjectionsSlide Number 42

tatiara pwa: groundwater resource condition and modelling results · 2017. 9. 4. · tatiara pwa:...

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