living lakes feasibility study – environmental report...living lakes feasibility study –...

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LIVING LAKES FEASIBILITY STUDY ENVIRONMENTAL REPORT

July 9 2012

prepared for

JDA Consultant Hydrologists

on behalf of

Department of Regional Development and Lands

by

Land Assessment Pty Ltd and Woodgis Environmental Consultants

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CONTENTS

ACKNOWLEDGEMENTS .......................................................................................................................... vi

ACRONYMS ........................................................................................................................................... vii

EXECUTIVE SUMMARY ............................................................................................................................ 1

1. INTRODUCTION ............................................................................................................................... 2

1.1. Background ............................................................................................................................. 2

1.2. Current Condition of the Lakes ............................................................................................... 4

1.3. Objectives................................................................................................................................ 5

2. ASSESSMENT FRAMEWORK ............................................................................................................ 6

2.1. Characterisation and Significance of Environmental Assets ................................................... 6

2.1.1. Wetlands ............................................................................................................................. 6

2.1.2. Vegetation ........................................................................................................................... 7

2.1.3. Flora and Fauna ................................................................................................................... 9

2.2. Potential Impacts and Approvals Processes ......................................................................... 10

2.2.1. Changes in Water Regime ................................................................................................. 10

2.2.2. Changes in Water Salinity ................................................................................................. 11

2.2.3. Impacts on Vegetation, Flora and Fauna .......................................................................... 12

2.2.4. Effects on Lake Ecology ..................................................................................................... 13

2.2.5. Drainage ............................................................................................................................ 14

2.2.6. Lake-bed Dredging ............................................................................................................ 14

2.2.7. Native Title and Aboriginal Heritage ................................................................................. 15

2.2.8. Governance and On-going Management Considerations ................................................ 16

3. LAKE TOWERRINNING ................................................................................................................... 17

3.1. Lake Values and Catchment Context .................................................................................... 17

3.2. Landforms and Soils .............................................................................................................. 20

3.2.1. Overview ........................................................................................................................... 20

3.2.2. Site Survey and Mapping Results ...................................................................................... 22

3.3. Vegetation, Flora and Fauna ................................................................................................. 26

3.3.1. Overview ........................................................................................................................... 26


3.3.3. Factoring Influencing Approvals ....................................................................................... 36

3.4. Aboriginal Heritage ............................................................................................................... 37

3.5. Existing Lake Modifications and Initiatives ........................................................................... 38

3.6. Living Lake Enhancements – Environmental Considerations ............................................... 39

3.6.1. ET1: Increase Re-diversion Capacity (Extra Culvert) ......................................................... 39

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3.6.2. ET2: Capercup Reserve Drain To Lake ............................................................................... 40

3.6.3. ET3: Dredging of Lake (increased depth) .......................................................................... 41

3.6.4. ET4: Groundwater Replenishment .................................................................................... 41

3.6.5. ET5: Rehabilitation Re-diversion Drain ............................................................................. 42

3.6.6. ET6: Refine Drainage from Outlet Swamp to Arthur River ............................................... 43

3.6.7. ET7: Modify Outlet Structure from Lake to Outlet Swamp .............................................. 44

4. LAKE EWLYAMARTUP .................................................................................................................... 45



4.2.1. Overview ........................................................................................................................... 47



4.3.1. Overview ........................................................................................................................... 53






4.6.1. EE1: Diversion ................................................................................................................... 66

4.6.2. EE2: Flushing ..................................................................................................................... 67

4.6.3. EE3: Dredging of Lake (increased depth) .......................................................................... 68

4.6.4. EE4: Groundwater Replenishment .................................................................................... 69

4.6.5. EE5: LEWG Option G32 ..................................................................................................... 70

4.6.6. EE6: LEWG Option G41 ..................................................................................................... 70

5. LAKE YEALERING............................................................................................................................ 71



5.2.1. Overview ........................................................................................................................... 74



5.3.1. Overview ........................................................................................................................... 80






5.6.1. EY1: Bund within Backswamps ......................................................................................... 91

5.6.2. EY2: Improvement of Outlet ............................................................................................. 92

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5.6.3. EY3: Dredging of Lake (increased depth) .......................................................................... 93

5.6.4. EY4: Groundwater Replenishment .................................................................................... 94

5.6.5. EY5: Gated System on Outlet Drain .................................................................................. 94

6. CONCLUSIONS ............................................................................................................................... 95

REFERENCES .......................................................................................................................................... 97

APPENDIX A SOIL DESCRIPTION SITE DATA ..................................................................................... 103

APPENDIX B LAKE MARGINS – TRANSECT DIAGRAMS .................................................................... 104

APPENDIX C FAUNA REPORT (Bamford Consulting Ecologists) ....................................................... 105

APPENDIX D RESULTS OF ABORIGINAL HERITAGE ENQUIRIES ........................................................ 106

APPENDIX E VEGETATION, FLORA AND FAUNA TABLES ................................................................. 107

FIGURES Figure 1: Location of Lakes ..................................................................................................................... 3 Figure 2: Lake Towerrinning – Aerial Image and Cadastre .................................................................. 17 Figure 3: Lake Towerrinning Catchment .............................................................................................. 18 Figure 4: Soil Landscapes - Lake Towerrinning Area ............................................................................ 21 Figure 5: Location of Soil Sites and Transects - Lake Towerrinning………………………………………………….21 Figure 6: Land Unit Mapping - Lake Towerrinning Area ...................................................................... 25 Figure 7: Extent of the Beaufort Vegetation System ........................................................................... 26 Figure 8: Vegetation System-Associations in Vicinity of Lake Towerrinning ....................................... 27 Figure 9: Vegetation Complexes in Vicinity of Lake Towerrinning ...................................................... 28 Figure 10: Vegetation Formations in Vicinity of Lake Towerrinning .................................................... 31 Figure 11: Extent of Secondary Salinisation within Capercup Nature Reserve……………………… ........... 35 Figure 12: Registered Aboriginal Sites in Vicinity of Lake Towerrinning .............................................. 37 Figure 13: Enhancements Considered in Living Lakes Project – Lake Towerrinning ........................... 39 Figure 14: Lake Ewlyamartup – Aerial Image and Cadastre ................................................................. 46 Figure 15: Lake Ewlyamartup Catchment ............................................................................................ 47 Figure 16: Soil-Landscapes - Lake Ewlyamartup .................................................................................. 49 Figure 17: Location of Soil Sites and Transects – Lake Ewlyamartup .................................................. 51 Figure 18: Land Mapping Unit - Lake Ewlyamartup Area .................................................................... 52 Figure 19: Extent of the Dumbleyung Vegetation System ................................................................... 53 Figure 20: Vegetation System-Associations in Vicinity of Lake Ewlyamartup ..................................... 55 Figure 21: Vegetation Formations in Vicinity of Lake Ewlyamartup .................................................... 58 Figure 22: Lake Ewlyamartup – Registered Aboriginal Sites (as at September 2010) ......................... 63 Figure 23: Lake Ewlyamartup – Registered Aboriginal Site ID 4541 .................................................... 64 Figure 24: Enhancements Considered in Living Lakes Project – Lake Ewlyamartup ........................... 66 Figure 25: Lake Yealering System… ...................................................................................................... 72 Figure 26: Lake Yealering –Cadastre .................................................................................................... 72 Figure 27: Lake Yealering Catchment ................................................................................................... 73 Figure 28: Soil Landscapes Lake Yealering Area ................................................................................... 75 Figure 29: Location of Soil Sites and Transects - Lake Yealering Area………………………………………………78 Figure 30: Land Unit Mapping - Lake Yealering Area ........................................................................... 79 Figure 31: Extent of Corrigin Vegetation System ................................................................................. 80 Figure 32: Vegetattion System-Associations in Vicinity of Lake Yealering.. ........................................ 81 Figure 33: Vegetation Formations in Vicinity of Lake Yealering .......................................................... 84 Figure 34: Lake Yealering – Registered Aboriginal Sites ...................................................................... 88 Figure 35: Enhancements Considered in Living Lakes Project – Lake Yealering .................................. 90

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TABLES

Table 1: Hydrological Framework for Lakes ........................................................................................... 3 Table 2: Native Title Claims Affecting the Lakes .................................................................................. 15 Table 3: Soil-Landscape Map Units – Lake Towerrinning Area ............................................................ 22 Table 4: Land Unit Descriptions - Lake Towerrinning Area .................................................................. 25 Table 5: Extents of Vegetation Associations in Vicinity of Lake Towerrinning .................................... 26 Table 6: Extents of Vegetation System-Associations in Vicinity of Lake Towerrinning ....................... 28 Table 7: Extents of Vegetation Complexes in Vicinity of Lake Towerrinning....................................... 29 Table 8: Likelihood of Significant Flora Occurring in Wetland Areas Around Lake Towerrinning ....... 33 Table 9: Soil Landscape Map Units - Lake Ewlyamartup Area .............................................................. 48 Table 10: Land Unit Descriptions - Lake Ewlyamartup ......................................................................... 52 Table 11: Extent of Vegetation Associations in Vicinity of Lake Ewlyamartup ..................................... 54 Table 12: Extents of System-Associations in Vicinity of Lake Ewlyamartup ........................................ 56 Table 13: Likelihood of Significant Flora Occurring in Wetland Areas Around Lake Ewlyamartup ..... 60 Table 14: Soil Landscape Map Units - Lake Yealering Area................................................................... 76 Table 15: Soil Landscape Map Units - Lake Yealering Area................................................................... 79 Table 16: Extent of Vegetation Associations in the Vicinity of Lake Yealering .................................... 81 Table 17: Extents of System-Associations in the Vicinity of Lake Yealering ........................................ 82 Table 18: Likelihood of Significant Flora Occurring in Wetland Areas Around Lake Yealering ............ 85

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ACKNOWLEDGEMENTS The authors wish to acknowledge the input of the following in contributing to this document. Members of the Living Lakes Steering Committee for their review and guidance, especially representatives from: Department of Regional Development and Lands Department of Water Department of Environment and Conservation Department of Indigenous Affairs

Bamford Consulting Ecologists for inputs relating to fauna. Attendees of Living Lakes workshops, community and departmental representatives who provided valuable ‘on-ground’ input to environmental aspects of the Feasibility Study, especially: Lake Towerrinning Ros Abbott Landowner Gary Abbott Landowner Donald Cochrane Landowner Ian Peirce Landowner Tereasa Pierce Landowner Geoff Whitaker Landowner Don Bennett Department of Agriculture Dr Richard George Department of Agriculture Michelle Gooding District Landcare Officer

Lake Ewlyamartup Greg Garlick Landowner Lance Mudgeway Consultant Hydrologist Marianne Perrie District Landcare Officer Mick Quartermaine Chair LEWG David Secomb Bird observer

Lake Yealering Ken Beattie Landowner Doug Corke Landowner Tim (Whippy) Dawes Landowner Ian Hills Landowner Matt Pockran Landowner Brad Degens Department of Water Natalie Manton Shire of Wickepin

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ACRONYMS

AHA Aboriginal Heritage (Act 1972)

AHD Australian Height Datum

ASS Acid Sulfate Soil

CAMBA China-Australia Migratory Bird Agreement

CAR Comprehensive, Adequate and Representative (reserve system analysis)

DAFWA Department of Agriculture and Food (WA)sulfate

DEC Department of Environment and Conservation

DIA Department of Indigenous Affairs (WA)

DOE Department of Environment

DOT Department of Transport (WA)

EP Environmental Protection (Act 1986).

EPA Environment Protection Authority (of WA)

EPBC Environment Protection and Biodiversity Conservation (Act 1999)

IBA Important Bird Area

JAMBA Japan -Australia Migratory Bird Agreement

JANIS Joint ANZECC/MCFFA National Forest Policy Statement Implementation sub-committee

JDA Jim Davies and Associates (Consulting Hydrologists)

LCDC Land Care District Committee

LEWG Lake Ewlyamartup Working Group

LTCLG Lake Towerrinning Catchment Landcare Group

NOI Notice of Intent

NPNCA National Parks and Nature Conservation Authority (WA)

PASS Potential Acid Sulfate Soil

PEC Priority Ecological Community

RDL (Department of) Regional Development and Lands

SLIP Shared Land Information Platform

SW South West

SWCC Southwest Catchment Council

TEC Threatened Ecological Community

WA West/ern Australia/n

WAWA Water Authority of Western Australia

Living Lakes Feasibility Study – Environmental Report

Land Assessment & Woodgis – Environmental Consultants Page 1

EXECUTIVE SUMMARY This Environmental Report forms part of the Living Lakes Feasibility Study prepared for the Department of Regional Development and Lands by a consultant team led by JDA Consultant Hydrologists. This report describes the environmental setting and values of the three lakes (Lakes Towerrinning, Ewlyamartup and Yealering) that were selected during an earlier stage of the Living Lakes Project. It outlines environmental considerations and provides an assessment of ‘environmental risk’ relating to a number of lake-enhancement options that have been developed and evaluated by JDA in terms of hydrological feasibility.

The environmental considerations for each lake are based on a review of existing environmental information, supplemented by site-specific field survey and mapping of landform, soil and vegetation conditions. In this report ‘environmental risk’ refers to this consultant’s assessment of the potential to adversely impact lake environmental values, and the associated potential proposed enhancement options to be deemed inappropriate during regulatory approval processes. The environmental risk assessment for lake enhancement options is qualitative. As part of a Feasibility Study, the level of assessment undertaken could only be of a relatively superficial nature aimed at identifying ‘make or break’ issues. Any quantification of environmental impacts requires more detail on predicted hydrological changes following the adoption of one or more enhancement options. It is the conclusion of this report that with the possible exception of lake dredging, the broadly defined engineering ‘enhancement options’ present no ‘fatal flaws’ of an environmental nature, subject to the resulting maximum water levels in each lake being such that they do not cause prolonged inundation (and possible death) of existing fringing native vegetation.

Specific environmental considerations are identified in relation to the location, design and management of engineering structures associated with the lake enhancement options. None of these considerations are ‘fatal flaws’ to lake enhancement in their own right. In this environmental context the enhancement options are feasible. Notwithstanding these conclusions, it is recommended that following any decision to implement enhancement options at one or more of the lakes, that RDL initiate a ‘Proponent Referral’ under Section 38 of Part IV of the EP Act to enable the EPA to make its determination on the need and level of any required environmental assessment and associated regulatory approvals.



1. INTRODUCTION

1.1. Background The Department of Regional Development and Lands (RDL) engaged a consultant team led by JDA Consultant Hydrologists (JDA) to investigate the feasibility of revitalizing up to three lake systems, to develop recreational, social and economic opportunities within rural Western Australia. The RDL Living Lakes initiative proposes to enhance existing lakes to create permanent and accessible water bodies using a program of engineering solutions such as drainage diversions and lake replenishment from groundwater. Environmental risk factors need to be considered as part of the feasibility study, and this component has been undertaken by environmental consultants Land Assessment Pty Ltd and Woodgis Environmental Assessment & Management, in conjunction with Bamford Consulting Ecologists. During an initial part of the Living Lakes initiative twenty five community-nominated lakes were assessed against a range of water resource, socio-economic, regional development and environmental considerations, and three lakes were short-listed for further study. As outlined in the JDA Feasibility Study report, these lakes were:

Lake Towerrinning in the Shire of West Arthur Lake Ewlyamartup in the Shire of Katanning Lake Yealering in the Shire of Wickepin.

Figure 1 shows the location of these lakes in relation to the biogeographic regions (DEC, 2012). Lake Towerrinning is located in the Jarrah Forest Biogeographic Region, and Lakes Ewlyamartup and Yealering are located in the Avon Wheatbelt Biogeographic Region. The Jarrah Forest Biogeographic Region covers 4,500,000 ha, of which 56% remains uncleared (Government of Western Australia, 2009). It is characterised by Jarrah-Marri forest on laterite gravels with Marri-Wandoo woodlands on clayey soils in its eastern portion (DEC, 2012). The Avon Wheatbelt Biogeographic Region covers 9,517,110 ha, of which 18% remains uncleared (Government of Western Australia, 2009). It is characterised by Proteaceous scrub-heath on residual lateritic uplands and derived sandplains; and mixed eucalypt, Sheoak, and Jam-York Gum woodlands on alluvials and elluvials (DEC, 2012).



Figure 1: Location of Lakes In combination with the biogeographic regions, Western Australia’s soil-landscape mapping hierarchy along with its hydrological framework provides a basis for characterising the environments of the three wetlands (lakes) as shown in Table 1. Table 1: Hydrological Framework for Lakes

Wetland / Lake

Soil-landscape Zone / System1

Drainage Basin Catchment / Management Area2

Wetlands / River system

Lake Towerrinning Eastern Darling Range Zone / Darkan System

Blackwood

Lower-middle Catchment (Management Zone 4 – Beaufort Zone)

Arthur River

Lake Ewlyamartup South-western Zone of Ancient Drainage/ Coblinine System

Blackwood

Upper Catchment (Management Zone 6 – Katanning Zone)

Coblinine River

Lake Yealering South-western Zone of Ancient Drainage/ Coblinine System

Avon Avon sub-catchment (Upper Avon River Section 20)

Upper Avon River – Yealering Lakes

References: 1. Schoknecht et al (2004) 2. De Silva et al (2000) and Brockman (2001, 2003)



From a broad landscape perspective, Lake Towerrinning occurs within the Eastern Darling Range Soil Landscape Zone (Schoknecht et al 2004). This is an area of relatively elevated slopes and rainfall occurring within undulating to rolling terrain formed by the dissection of a gently undulating lateritic plateau. Further inland, Lakes Ewlyamartup and Yealering occur within the South-western Zone of Ancient Drainage, a much flatter, sediment filled landscape with sluggish drainage systems and lower rainfall. From a broad catchment perspective, Lakes Towerrinning and Ewlyamartup form part of the Blackwood River Basin which covers an area of about 22,500 km2 extending approximately 300 km inland from the river mouth at Augusta (De Silva et al 2000). Lake Yealering however forms part of the Avon River Basin which covers an area of approximately 120 000 km2 extending inland from the river’s discharge into the Swan Canning estuary near Perth (Department of Water 2006). Together, the Blackwood and Avon River Basins occupy the major part of Western Australia’s wheatbelt region. In relation to land tenure, all three lakes occur within Crown land as reserves where the vesting purpose includes a recreational use component.

1.2. Current Condition of the Lakes The current environmental condition of all three lakes reflects the effects of vegetation clearing within their catchment areas to facilitate productive agricultural development. To a varying extent, each of the lakes has also been subject to more recent localised hydrological interventions and none are representative of an unaltered ‘natural’ environment. Land clearing and the replacement of deep-rooted perennial species with shallow-rooted annual cropping species in the Wheatbelt region of Western Australia has resulted in a reduction in water use by vegetation (evapotranspiration). This has in turn caused a rise in watertables and mobilisation of salt previously stored deep within the soil profile – a process leading to salinity within many watercourses and wetlands in the Wheatbelt, particularly within the Zone of Ancient Drainage. Relatively recent hydrological interventions affecting the current water regime in the lakes include a creek re-diversion structure and gated outlet at Lake Towerrinning, modifications to the inlet channel and areas of dredging at Lake Ewlyamartup, and a stream diversion structure near the outlet at Lake Yealering. Lake Towerrinning In its preliminary advice on the Living Lakes Feasibility Study the Department of Environment and Conservation (DEC) recognise the existing works constructed on private property and their effect on managing water levels within Lake Towerrinning (D Bennetts pers. comm. Oct 2011). Given the vesting of this lake as a nature reserve (albeit for the purpose of aquatic sports as well as conservation) DEC advises that modifications to water levels and onsite works to achieve the Living Lakes outcomes are likely to require approval from the Conservation Commission as well as



assessment and approval under the Environmental Protection Act 1986 (EP Act). As the managing agency for Lake Towerrinning, DEC have also advised that details of any further development at the site should be submitted for its approval to ensure there are no negative impacts on the nature reserve or nature conservation values. Lakes Ewlyamartup and Yealering The effect of salinization and hydrological interventions to Lakes Ewlyamartup and Yealering is also recognised by DEC. Although these lakes are not contained within nature reserves existing environmental values should not be diminished, and preferably enhanced, as a result of any proposed engineering measures. DEC advise that site development for these lakes may also require assessment and approval under the Environmental Protection Act 1986 (EP Act).

1.3. Objectives The objective of this report is to provide information to assist the determination of feasibility for lake enhancement options, and the minimization of any associated environmental risks. This is initially addressed by:

outlining the framework for considering environmental assets and their significance in WA, and; identifying potential environmental impacts from lake enhancement measures and the

associated regulatory approval processes.

For each lake, specific details are then provided on;

characteristics of the natural environment in the immediate vicinity of each lake, and environmental assets with potential to be affected by lake modification.

The aim in collating this information from both desktop research and field investigations (vegetation and soils only) is to identify any potential environmental ‘fatal flaws’ in terms of regulatory approvals, as well as environmental matters requiring more detailed consideration during Stage 2 of the Living Lakes initiative (design of concept plans and costings for lake enhancements).



2. ASSESSMENT FRAMEWORK

2.1. Characterisation and Significance of Environmental Assets

2.1.1. Wetlands

A wetland is defined in Schedule 5 of the Environmental Protection Act 1986 as: ‘an area of seasonally, intermittently or permanently waterlogged or inundated land, whether natural or otherwise, and includes a lake, swamp, marsh, spring, dampland, tidal flat or estuary’. Lakes and wetlands are an intrinsic part of the hydrology of a region and are widely recognised as significant for their ecological, hydrological, social and economic values (EPA, 2004). Wetlands / lakes can be categorised, and their significance assessed, at a regional scale in terms of: international treaties (e.g. listed under the Ramsar Convention on Wetlands of International

Importance, and wetlands supporting birds listed in the Japan Australia Migratory Bird Agreement (JAMBA) and the China Australia Migratory Bird Agreement (CAMBA))

listing in A Directory of Important Wetlands in Australia (Environment Australia 2001) vesting of wetlands for conservation purposes listing as Important Bird Area (IBA) by Birdlife Australia (formerly Birds Australia) information on ‘WetlandBase’.

International Significance The Government of Australia maintains a list of (currently 64) wetlands of international importance which are subject to international treaties (e.g. the Ramsar Convention) of which the Government of Australia is a signatory). National Significance The Government of Australia maintains a list of (currently 904) wetlands of national importance included on the list of Matters of National Environmental Significance and protected under the Commonwealth EPBC Act 1999. These wetlands, which are listed in A Directory of Important Wetlands in Australia, were identified on the basis of meeting at least one of the following criteria:

It is a good example of a wetland type occurring within a biogeographic region in Australia It is a wetland which plays an important ecological or hydrological role in the natural functioning

of a major wetland system/complex It is a wetland which is important as the habitat for animal taxa at a vulnerable stage in their life

cycles, or provides a refuge when adverse conditions such as drought prevail The wetland supports 1% or more of the national populations of any native plant or animal taxa



The wetland supports native plant or animal taxa or communities which are considered endangered or vulnerable at the national level

The wetland is of outstanding historical or cultural significance. Birdlife Australia (formerly Birds Australia, and prior to that the RAOU) maintains a list of (currently 314) wetlands that are Important Bird Areas (IBAs) having being identified on the basis of: Globally threatened species (the site must regularly support threshold numbers of a Critical,

Endangered or Vulnerable species, as categorised by the IUCN Red List); Restricted-range species (the site forms one of a set protecting 'restricted-range species' (birds

with a global range of <50,000 km2) Biome-restricted species Congregations (The site supports > 1% of the world population of a waterbird (similar to Ramsar

Convention criteria) or seabird). State Significance Western Australia’s Department of Environment and Conservation maintains a state-wide on-line wetlands database, ‘WetlandBase’, for the purpose of disseminating wetland information. It includes various biophysical datasets, map datasets, and linkages to publications from which the environmental values and significance of the three wetlands has been determined, and reported herein. Key monitoring data relating to water level, salinity and pH within Lakes Towerrinning and Yealering are also contained within the Department’s recent report on its South West Wetlands Monitoring Program Report (Lane et al 2011). Other resources addressing wetland values within the area of relevance include regional natural resource management (NRM) publications by South West Catchments Council (2001, 2004) and the Avon Catchments Council (2005), and earlier wetland inventories such as that by Pen (1997).

2.1.2. Vegetation

Vegetation can be categorised, and its significance assessed, at a regional scale in terms of: Ecological Communities Vegetation Associations and Complexes species richness vesting of land for conservation purposes.

Ecological Communities The DEC maintains a state-wide dataset of Ecological Communities that: represent naturally occurring biological assemblages that occur in a particular type of habitat. were mapped at varying scales for individual occurrences that were identified as significant.



Ecological Communities are identified as regionally significant when they are listed as: Threatened Ecological Communities (TECs), which are ecological communities at risk of

extinction through human action or inaction Priority Ecological Communities (PECs) for which there is insufficient information available for

consideration as a TEC, or which are rare communities that are not currently threatened. The detailed descriptions for each of the ecological community conservation status codes used by the DEC are provided in Appendix E. In addition to this recognition of conservation significance, 17 WA TECs are also listed as Matters of National Environmental Significance and protected under the Commonwealth EPBC Act 1999. Vegetation Associations and Complexes The DEC maintains a state-wide dataset of Vegetation Associations that: represent broad scale vegetation units defined in terms of vegetation structure and floristics were mapped at a scale of 1:50 000 with consistent nomenclature (Shepherd et al 2002) were further refined into Vegetation System-Associations (when defined in terms of their

occurrence in specific Vegetation Systems) and used in the Comprehensive, Adequate and Representative (CAR) reserve system analysis for Western Australia (Government of Western Australia, 2009).

Also of relevance, but just to Lake Towerrinning in this study, the DEC maintains a dataset of Vegetation Complexes for the Darling Range bioregion that: represent broad scale vegetation units defined in terms of consistently repeating plant

communities in the context of landform-soil units (using climatic, floristic, geomorphic and vegetation structural data), for which plant communities may occur in more than one complex but the relative proportions of plant communities vary between complexes (Government of Western Australia, 2000)

were mapped at a scale of 1:50,000 used in the development of the WA Regional Forest Agreement.

Vegetation Associations and Vegetation Complexes are regionally significant when: the total percent remaining is near or below a threshold of 30. At this threshold the WA EPA

would generally apply a default presumption against clearing in the areas subject of this report. This position having been established for non-constrained areas (which include the Shires of West Arthur, Katanning and Wickepin) in a number of documents including the Position Statement No. 2 - Environmental Protection of Native Vegetation in Western Australia (EPA, 2000).



Species Richness Broad scale species richness estimates have been produced by CALM/DEC: in the Jarrah Forest Bioregion, species richness was modelled by CALM (1998) on the distirbution

of 1929 native plant species within one by one kilometre grids (fauna was not included in the model due to data limitations)

in the wheatbelt, broad scale modelling was undertaken for 1992 terrestrial species (1335 plants and 587 animals) by McKenzie, Gibson, Keighery & Rolfe (2004) and 1887 wetland or wetland associated species (986 plants and 901 animals) by Halse, Lyons, Pinder & Sheil (2004).

Areas of regionally significant high species richness occur when: in the Jarrah Forest Bioregion, they were identified as potentially having national estate value by

the Regional Forest Agreement Steering Committee (1998) in the development of the Regional Forest Agreement

in the wheatbelt, they were in or near potential candidate biodiversity recovery catchments proposed by Walshe, Halse, McKenzie & Gibson (2004) to optimise preservation of species.

Vesting of land The WA Land Information Authority maintains cadastral information which can be used to identify lands vested for conservation purposes (e.g. Nature Reserves vested with the Conservation Commission and managed by the Department of Environment and Conservation for the purpose of ‘Conservation of Flora and Fauna’).

2.1.3. Flora and Fauna

Flora and fauna can be categorised, and its significance assessed, at a regional scale in terms of: international treaties threatened species lists priority species lists populations that are at the limits of distribution ranges, or outliers populations with distinctive features/unusual forms.

The Government of Australia maintains a list of migratory birds which are subject to international treaties, of which the Government of Australia is a signatory, and are included on the list of Matters of National Environmental Significance and protected under the Commonwealth EPBC Act 1999. Threatened Flora, and Threatened and Schedule Fauna are species declared under the Wildlife Conservation Act 1950, by the Western Australian Minister for the Environment on the basis they are considered to be in danger of extinction, rare or otherwise in need of special protection. In addition to this recognition of significance by the Government of Western Australia, some threatened species are additionally also listed by the Government of Australia as Matters of National Environmental Significance and protected under the Commonwealth EPBC Act 1999.



The Department of Environment and Conservation also maintain lists of Priority Flora and Priority Fauna. Three categories cover poorly known species and species that have been adequately surveyed and are considered to be rare but not currently threatened. The definitions for each of these categories of conservation significant species are listed in Appendix E. Populations of species at the limits of distribution ranges, or outliers, or with distinctive features/unusual forms are generally identified through detailed surveys. Detailed surveys were not undertaken for this project.

2.2. Potential Impacts and Approvals Processes The assessment of potential impacts or ‘environmental risk’ undertaken in this report can only be of a relatively superficial nature, and is aimed at identifying ‘make or break’ issues as part of the Feasibility Study. Any further qualification of impacts or risk can only be made after detailed engineering designs are produced. It is important to highlight that where enhancement options may cause significant environmental impacts these would need to be quantified and approvals sought as required under relevant legislation. It is noted that the Department of Sustainability, Environment, Water, Population and Communities (2012) defines a significant impact (under the EPBC Act 1999) as ‘an impact which is important, notable, or of consequence, having regard to its context or intensity. Whether or not an action is likely to have a significant impact depends upon the sensitivity, value, and quality of the environment which is impacted, and upon the intensity, duration, magnitude and geographic extent of the impacts’. A discussion of the potential range of impacts and factors to be considered follows.

2.2.1. Changes in Water Regime The objective of the Living Lakes project is to revitalise the lakes through the addition and/or greater retention of water. As a result, changes to the existing water regime are inevitable. However such changes are intended to be of benefit to the social and recreational use opportunities and to occur without significant detriment to existing environmental values. In many wheatbelt lakes a rising saline watertable induced by land clearing has led to inundation and death of fringing wetland vegetation. In areas where watertables appear to have reached a new equilibrium, dead tree ‘stags’ are now a common feature of the salt lake margins. Beyond the current ‘maximum water levels’ the remaining living fringing vegetation fulfills a number of important roles including fauna habitat, shoreline stabilization, and as a filter against the input of sediments and nutrients from adjacent lands. Engineering options which raise the lake’s current



maximum water levels for a substantial period can risk damage to this vegetation and undermine these important roles. Sustained raising of maximum water levels within lakes can also increase the risk of waterlogging and salinity within adjacent farmland. Inundation over a prolonged period of time is likely to result in death of fringing wetland vegetation (due to either waterlogging and or salinity). Furthermore, where a lake’s fringing vegetation is narrow, the ability of that vegetation to progressively recolonise and migrate upslope in response to increasing lake level is often limited by the proximity of clearing rather than the eco-physiology of plants. To prevent the risk of fringing vegetation being adversely affected, it is recommended that the engineering options, whilst aiming to increase the depth and longevity of water in each lake, should avoid any sustained raising the lake’s existing maximum water level. This level generally lies just above the line of live trees tolerant of some inundation (often Saltwater Sheoak and/or Paperbarks). A conservative approach is to consider risk increasing as water is progressively raised above this level (which has been estimated from the lake margin transects included in Appendix B).

2.2.2. Changes in Water Salinity Salinity is the single factor that has greatest influence of flora and fauna in wheatbelt wetlands (Halse et al., 2004). Most waterbodies in the Wheatbelt have been affected by secondary salinization (Halse, Williams, Jaensch, & Lane, 1993) and a return to freshwater conditions is generally considered to be not feasible without substantial lowering of saline watertables through measures such as: widespread revegetation of catchments (often not practical in an agricultural landscape) extensive drainage (often not practical due to effects on ‘downstream areas’).

The following points summarise the effects of increased salinity:

Salinization is likely to detrimentally change both invertebrate and waterbird communities (Cale et al., 2004).

If a lake becomes more saline then associated plant communities are likely to be replaced by a smaller suite of salt tolerant forms. Samphires are often the only perennial vascular plants that can survive on salty, waterlogged soils.

Salinity of soil adjacent to a lake is often poorly correlated with salinity in the waterbody (Halse, Lyons, Pinder, & Sheil, 2004).

Waterlogging appears to exacerbate the effects of salinity on fringing vegetation (Carter, Colmer, & Veneklaas, 2006).



Furthermore, in relation to conditions for waterbirds, Halse, Williams, Jaensch, & Lane (1993) report that waterbodies supporting the greatest number of waterbird species tend to be brackish (rather than fresh or saline) with trees or shrubs and sedges. Although seasonal variations in lake salinity can occur, and be influenced by the range of engineering options being considered as part of the Living Lakes initiative, restoration of water quality to freshwater status is highly unlikely for Lakes Yealering and Ewlyamartup where there is low rainfall and high evaporation. This underscores the importance of retaining or improving water quality within Lake Towerrinning which is located in the relatively higher rainfall area and currently contains water of generally ‘brackish’ quality. Although a primary aim of engineering aspects of the Living Lakes initiative is to increase the quantity or longevity of water in lake, maintaining or improving the quality of the water is also important. This is because the desired increase in social and recreational use values associated with increased quantity of water can be compromised if that water is of poorer quality due to hypersaline (or nutrient enriched) conditions. This can generally be addressed by having adequate lake throughput or flushing, in combination with appropriate catchment land management practices.

2.2.3. Impacts on Vegetation, Flora and Fauna Potential impacts need to be considered for vegetation (e.g. types and assemblages) and for identified species or groups of species that are most at risk from lake modification. The species and groups of species requiring particular consideration are those that are: located, or utilise areas, within approximately 1 m of elevation of the typical high water level of

the lake, or are in an area likely to be impacted by earthworks, and restricted in extent/distribution in the immediate vicinity of the lake, and intolerant of salinity levels recorded in the lake, and intolerant of inundation.

Wetlands, vegetation and species of recognized ’environmental significance’ have a greater potential to result in a ‘make or break’ issue. In its preliminary advice on the Living lakes project the Department of Environment and Conservation (DEC) advise that environmental approval will be required if the flora, fauna or communities impacted by the proposed developments are listed as ‘Threatened’ or if they are listed as ‘Migratory Species’ under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (D Bennetts pers. comm. Oct 2011).



The significant flora and fauna, and groups of species (e.g. vegetation types and biodiversity assemblages) that are the focus of this report are those:

identified through the lists outlined within Section 2.1 and are associated with, or dependent upon, wetlands and are likely to occur in the vicinity of the lakes.

It is important to highlight that where the enhancement options involve the clearing of remnant vegetation, the definition of ‘clearing’ under the EP Act includes any substantial damage to indigenous vegetation (terrestrial or aquatic) including the effects of draining or flooding of land.

2.2.4. Effects on Lake Ecology In Wheatbelt lakes, four alternate stable ecological states have been identified by Davis et al. (2001a). These are: clear, aquatic plant-dominated systems clear, benthic microbial or benthic mat-dominated systems (these have a thin layer of algal cells

and bacteria on the bed of the lake) turbid (cloudy) phytoplankton-dominated systems turbid, sediment-dominated systems (relatively rare with poor light penetration into water

column preventing proliferation of algae and aquatic plants). Davis et al. (2001a) reported that clear, macrophyte-dominated systems support the richest and most abundant invertebrate and waterbird faunas, and in Wheatbelt lake systems the main salt tolerant species in this ‘state’ are Ruppia, Lepilaena and Lamprothamnium. Further increases in salinity generally result in a shift to a benthic microbial community dominated system, or to one dominated by benthic mats, composed mostly of cyanobacteria and halophilic (salt-loving) bacteria. Turbid, phytoplankton-dominated systems can occur in both freshwater and saline systems where nutrients are in plentiful supply. Benthic mats or algal blooms dominate where salinities and nutrients are too high to enable aquatic plants to germinate and persist. In relation to consideration of lake ecology / water quality issues and power boating activity, Froend (1986) conducted a study of water quality at Lake Towerrinning and reported that mixing of water by power boats can not only re-suspend sediments but also the nutrients held by the sediment. He concluded however that power boating activity was not considered to significantly contribute to the (then) ecological problems within Lake Towerrinning. The effects of power boating can however conflict with re-establishment of fringing vegetation, and cause shoreline erosion and subsequent damage to tree roots if speeds close to shore are excessive.



2.2.5. Drainage Where an owner or occupier of land wishes to drain or pump groundwater for the purpose of controlling salinity, a Notice of Intent is required to be lodged with the Commissioner of Soil and Land Conservation at least 90 days before discharging water (Department of Agriculture 2004). This requirement, under Regulation 5 of the Soil and Land Conservation Regulations 1992 associated with the Soil and Land Conservation Act 1945, could affect works proposed under the Living Lakes Initiative if deep drainage or pumping (involving management of groundwater rather than just surface water) is required. Where drainage (or stream diversion) options involve interference with the bed or banks or a watercourse, a permit is also required to be obtained from the Department of Water under Sections 111, 17 and 21A of the Rights in Water and Irrigation Act 1914. In addition to the effects of increased volumes of water and salt loads on lake drainage discharge areas, the potential acidity (pH < 5.5) of any intercepted saline groundwater can also be a matter of environmental concern due to the capacity of such water to acidify lakes and decrease aquatic life in saline systems (Department of Water 2009).

2.2.6. Lake-bed Dredging

Dredging involves removal of lake-bed sediment and the potential effects of this can include:

Removal of organic matter in the sediment

Acidification of the waterbody

Change in bathymetry.

Removal of organic matter in the sediment

Ruppia, Lepilaena and Lamprothamnium are the main species of salt tolerant aquatic plants found in Wheatbelt lakes and the seeds and spores of these species are probably present in the sediments of almost all Wheatbelt lake systems (Department of Environment 2005) although successful germination requires the right combination of conditions. In seasonal/intermittent lakes, life-cycles of aquatic organisms have evolved to enable survival during seasonal fluctuations in salinity and dry phases. Lake sediments can contain a store of buried and hidden organisms, seeds (seed banks) and eggs (egg banks) of species that remain dormant when the systems are dry, and enable recolonisation of waterbodies on reflooding (DoE 2005). In view of the above, and depending on the extent of lake area affected, dredging has the potential to remove significant amounts of organic matter and adversely affect a lake’s assemblage of aquatic plants and animals.



Acidification of the waterbody Acid Sulfate Soils (ASS) is the common name given to naturally occurring soils and sediments containing sulphide minerals, predominantly pyrite (an iron sulphide). In an undisturbed state below the water table, these soils are benign and non-acidic. However, if ASS are contained within lake bed sediments and then exposed to the atmosphere following dredging, the sulphides may react with oxygen to form sulphuric acid. This can result in the release of heavy metals which can adversely affect water quality and associated ecosystems, and cause corrosion of engineering works and infrastructure. Areas of disturbed ASS, may be classified as contaminated sites under provisions of the Contaminated Sites Act 2003. In a regional context, Shand and Degens (2008) have estimated that the extent of acidic groundwater in the soil zones containing Lake Towerrinning, Lake Ewlyamartup and Lake Yealering is 10-19%, 30-39% and 30-39% respectively. Change in bathymetry. Dredging offers the potential to increase water depth without increasing the area of inundation and therefore with lesser impact on fringing vegetation. It also provides an opportunity to create island refuges for waterbirds from predators. Steeper slopes on lake beds are also likely to reduce the extent/duration of shallow water for shorebirds.

2.2.7. Native Title and Aboriginal Heritage The three lakes are encompassed within various applications for Native Title that encompass significant portions of Western Australia’s South West and Great Southern regions. Table 2 lists the application information and the lakes affected. Table 2: Native Title Claims Affecting the Lakes

Application No (Federal Court)

Applicant Lake Area Affected Registration history

WAD6006/03

Anthony Bennell & Ors v State of Western Australia (Single Noongar Claim Area 1)

Lakes Towerrinning, Ewlyamartup and Yealering.

Not Accepted for registration

WAD6134/98 Allan Bolton, Glen Colbung, Dallas Coyne & Others on behalf of the Southern Noongar Families -v- the State of Western Australia & Others

Lake Ewlyamartup

Registered from 18/11/1996.

WAD6274/98 L Belotti & ors on behalf of Nyungar People (Gnaala Karla Booja)

Lakes Yealering and Towerrinning


WC98/70 Alan Bolton, Hazel Brown, Glen Colbung & Ors -v- the State of Western Australia & Ors (Wagyl Kaip)

Lake Ewlyamartup


Source: National Native Title Tribunal - Application Information and Extract from the Register of Native Title Claims



The Aboriginal Heritage Act 1972 (AHA) was introduced in Western Australia to protect Aboriginal heritage. The AHA recognises Aboriginal peoples' strong relationships to the land, which may go back many thousands of years. The AHA provides automatic protection for all places and objects in Western Australia that are important to Aboriginal people because of connections to their culture. These places and objects are referred to as Aboriginal Sites. A search for Registered Aboriginal Sites in the vicinity of the three lakes was conducted through the Aboriginal Heritage Inquiry System of the Department of Indigenous Affairs (DIA). The results are contained in Appendix D. As a result of the identification of any Registered Aboriginal Site it is likely that the Department of Indigenous Affairs will require further investigation of site values and consultation by a suitably qualified consultant prior to any works which might affect the site. DIA also advise that: Following the identification of potential Aboriginal heritage values, and in conjunction with consultation with the relevant Aboriginal community(s), a detailed risk assessment could be completed as to whether the proposed (Living Lakes enhancement) options would impact upon Aboriginal heritage values (and the degree of impact should it be relevant).

2.2.8. Governance and On-going Management Considerations Engineering options to enhance lake levels or improve water quality need not be restricted to immediate lake margins or in-lake areas. Works are commonly required to be undertaken on private land within a lake’s catchment area and governance and on-going management arrangements may need to be addressed. Landholder support is therefore essential. The Fence Road arterial drainage project at Lake Dumbleyung (Department of Water 2006, 2011), as well as the history of existing achievements within the Lake Towerrinning catchment (George et al 1995) provide relevant case studies. In addition to formal arrangements for on-going management of any engineering structures established on private land, the need for complimentary catchment-scale land management actions is widely recognised (for example, Lake Towerrinning Catchment Landcare Group 1992, 1994; Lake Ewlyamartup Working Group 2010). These actions include strategic re-vegetation near lake margins and watercourses, establishment of perennial pastures, and fencing waterways.



3. LAKE TOWERRINNING

3.1. Lake Values and Catchment Context Lake Towerrinning is a permanent and brackish wetland of approximately 180 ha (Cale et al., 2004) and forms part of the ‘Arthur River Wetlands System’ within the Blackwood Basin. Although Lake Towerrinning is not a Ramsar wetland and is not listed in the Directory of Important Wetlands in Australia (Environment Australia 2001) it is a regionally significant wetland within the South West Regional Strategy for Natural Resource Management (South West Catchments Council – SWCC 2004, 2005) and is an important habitat and drought refuge for waterbirds (Pen 1997). Lake Towerrinning is predominantly contained within A Class Nature Reserve No 24917 (Figure 2). This reserve is vested with the Conservation Commission for the purposes of ‘Conservation of Fauna, Protection of Flora, Aquatic Sports’ and is managed by the Department of Environment and Conservation (DEC). The central to south eastern portion of the lake is leased to the Shire of West Arthur and is a popular venue for recreation including water skiing and aquatic sports, although in low rainfall years inadequate water depth and algae build up can result in closure of the lake. Correspondence from the Department of Transport (DoT) indicates that a minimum depth of 2-3m is generally recommended for skiing, although private ski clubs will often operate with 1.2 to 1.3m depth. DoT have recommended closure of Lake Towerrinning at about 1.6m depth.

Figure 2: Lake Towerrinning – Aerial Image and Cadastre Data Source: Landgate Map Viewer - online image - accessed Sep 2011



The Lake Towerrinning catchment extends over approximately 12,500 ha in the southern part of the Shire of West Arthur (George and Bennett 1992) and is roughly bisected into equal areas upstream and downstream of the confluence of its two main tributaries, Cordering Creek and Morlup Creek. (Figure 3). Lake Towerrinning sits at the bottom of the catchment above the floodplain of the Arthur River into which it discharges.

Figure 3: Lake Towerrinning Catchment Map not to scale Source: Adapted from Lake Towerrinning Landcare Group (1994) In response to increasing salinity of the lake and a predicted increase in salt-affected agricultural land, the Lake Towerrinning Catchment Landcare Group (LTCLG) formed in 1989 in order to restore the then degraded wetland of Lake Towerrinning, and to encourage profitable and conservation based farming practices in their catchment (George et al., 1995).

Re-diversion Structure

Inlet Swamp

Arthur River

Outlet Swamp

Capercup Reserve



The LTCLG attracted scientific and technical assistance from the then Department of Agriculture and the Water Authority of Western Australia (WAWA) to undertake a hydrological assessment of the surface catchment and develop an action plan. This plan identified that water quality could be improved by re-diverting fresher water into the lake from the Morlup and Cordering Creeks within its catchment. These creeks had originally flowed into the lake, but due to erosion of a firebreak in the 1950’s, water had been lost into the adjacent Darlingup Creek catchment (George and Bennet, 1992). An engineering solution was devised which led to the construction in February 1993 of a re-diversion structure at the junction of the Morlup and Cordering Creeks. This structure allows the initial more saline spring follows to continue into the adjacent Darlingup Creek catchment, but as water volumes increase in winter the increasingly fresher flows spill over the structure and into the 12 km waterway that leads to the lake. The effect on Lake Towerrinning of the re-diversion structure and associated land management initiatives within the catchment is widely viewed as a success, with the Landcare Group (LTCLG) winning the State and National Landcare Australia Awards in 1994. Since the re-diversion structure was commissioned, the salinity (electrical conductivity) of the lake water has remained below 2500 mS/m on most observation dates (van Wyk and Raper, 2008). As part of a land salinity target setting exercise the same authors reported a landholder-based estimate that 12% of catchment was affected at that time by salinity but with a predicted increase up to 20 – 25% by 2028. In relation to the waterway downstream from the re-diversion structure, George and Bennett (1992) considered it to be the minimum size needed and emphasised the importance of cleaning and maintenance. In 1994 the same authors, in common with Hazell (2003), commented that if stream salinities were to increase, the effectiveness of the re-diversion may be compromised. Furthermore in recent years the quality of water in the lake’s ‘outlet swamp’ at the edge of the Arthur River floodplain has been of concern to the landholder and owner of the adjacent caravan park, suggesting inadequate flushing and release of water from the lake. Away from the immediate lake environment, Capercup Reserve (No 31209) approximately 8 km to the northwest (Figure 3) is an important biodiversity asset within the catchment. Capercup is an A class Nature Reserve vested with the Conservation Commission for the purposes of ‘Conservation of Flora and Fauna’ and is managed by DEC. The next closest conservation estate is Wild Horse Swamp Nature Reserve (Reserve 1740) about 20 km downstream to the southwest of Lake Towerrinning. As part of a program for setting resource condition targets for vegetation assets affected by salinity in the South West Natural Resource Management Region, landholders in the catchment, in conjunction with the Department of Agriculture and Food (DAFWA), estimated that 30 - 40% of the Capercup Nature Reserve is currently affected by salinity and set a target for stabilisation. The occurrence of salinity here is related to underlying geological structures including the Kojonup Fault



and the Towerrinning Palaeochannel (George et al 1994). The set target is for the area affected by salinity in this reserve to increase by no more than an additional 10 %t (Van Wyk and Raper 2008). In consideration of the history of natural resource management in the catchment, the focus of the Living Lakes Feasibility Study in relation to Lake Towerrinning has been to review and build upon the achievements of the Landcare Group and associated government agencies, and potential engineering options for ‘future proofing’ the lake and Capercup Reserve against future possible deterioration.

3.2. Landforms and Soils

3.2.1. Overview The Department of Agriculture and Food’s broad-scale soil-landscape mapping over the south west agricultural area (http://spatial.agric.wa.gov.au/slip) provides an initial framework for consideration of the Lake Towerrinning environment. Soil landscape systems are defined as ‘areas with recurring patterns of landforms, soils and vegetation’ (Schoknect et al., 2004). The study area consists of two portions of soil landscape systems, described by Percy (2000) as follows: Darkan: Gently undulating to rolling rises and low hills, and narrow alluvial plains of the

Blackwood, Arthur and Hillman Rivers. Mainly sandy gravels, especially duplex sandy gravels, with areas of grey deep sandy duplex soils and granite or adamellite outcrops.

Boscabel: Gently undulating rises and narrow alluvial plains. Mainly deep sandy gravels, usually pale coloured, with grey sandy duplex soils, shallow and duplex sandy gravels.

In the Duranillin - Moodiarrup locality these systems are divided into a number of subsystems and phases as shown in Figure 4. Table 3 provides a description of relevant mapping units. The Lake Towerrinning catchment occurs within a landscape characterised by gently undulating rises, low hills, narrow incised valleys and broad flats. The broad flats, which include Lake Towerrinning and the adjacent ‘inlet and outlet swamps’, form around 20 % of the catchment landscape and are subject to seasonal inundation which raises the potential for salinisation. Areas of particular susceptibility occur in proximity to the lake’s inlet and outlet swamps.



Figure 4: Soil Landscapes - Lake Towerrinning Area Source: Background – Department of Agriculture and Food - Soil landscape systems (Percy 2000) accessed via Landgate Shared Land Information Platform (SLIP).



Table 3: Soil-Landscape Map Units – Lake Towerrinning Area Soil - Landscape Map Units

Description (dominant soils and landform)

Darkan System: (Dk) Gently undulating to rolling rises and low hills, and narrow alluvial plains. Main soils are duplex sandy gravels.

Dk1 Upper slopes, crests and breakaways. Gravelly soils.

Dk2i Lower to upper slopes. Gravelly soils.

Dk3 Mid to upper slopes. Duplex soils and loamy earths.

Dk4 Footslopes and lower slopes. Sandy duplex, and gravelly soils.

Dk5 Valley flats and narrow plains. Saline wet soil and sandy duplex soils.

Dk5w Swamps and lakes.

Dk6f Footslopes. Gravelly soils.

Dk6i Gravelly rises.

Dk7 Dunes and lunettes.

Boscabel System (Bo) Gently undulating rises and narrow alluvial plains. Main soils are deep sandy gravels.

Bo1 Upper slopes and crests. Gravelly soils.

Source: Percy, H.M. (2000). Katanning Area Land Resources Survey, Land Resources Series No. 16, Department of Agriculture, Perth.

3.2.2. Site Survey and Mapping Results Given the broad scale of soil landscape mapping shown in Figure 5, some ‘on-ground’ variation can be expected in soil and landform conditions. More detailed mapping of the component ‘land units’ (landform - soil types) was therefore undertaken by Land Assessment Pty Ltd in late February 2012 as a basis for understanding the local environmental setting and the possible implications of lake enhancement options. Soil and landform conditions were examined through aerial photo interpretation and a subsequent 3 – 4 day field survey period during which soils were described at 22 geo-referenced ‘hand auger’ sites associated with, but not limited to, a lesser number of lake margin transects as shown in Figure 5. At each observation site, soils were classified in accordance with the Department of Agriculture and Food’s WA Soil Group nomenclature (Schoknecht, 2002) and the landforms described according to its Land Evaluation Standards (van Gool et al., 2005). Representative soil samples were obtained from a number of sites for subsequent analysis of soil pH and salinity. Appendix A provides site summaries and associated data from the field survey work.



Figure 5: Location of Soil Sites and Transects - Lake Towerrinning



The resulting land unit mapping for Lake Towerrinning is shown in Figure 6: and described in Table 4. Although site numbers were not sufficient to fully characterise soil conditions, the land units nevertheless provide significantly more detail than the existing published soil landscape mapping. In conjunction with the detailed vegetation mapping by Woodgis Environmental Assessment & Management, the land unit mapping provides an appropriate framework for consideration of areas around the lake where impacts may arise from any future changes to local hydrological conditions. Of particular relevance is that soil auger borings show a ‘clay core’ is present within the central portion of the lunette (L1) on the eastern side of the lake, whereas the sandy lower portions (L2) are more permeable and susceptible to throughflow. Further detail of landform, soil and vegetation inter-relationships is provided within lake margin cross-section transect diagrams T1 – T13 contained in Appendix B. Transect diagrams were produced from field measurements involving a digital laser rangefinder, clinometer, staff gauge and measuring tape. Transect diagrams in Appendix B started (zero point), where possible, at water level at the time of field work. Actual water level at that time, in metres AHD, has been determined by correlation to reference points (such as staff gauges) that were subsequently surveyed by JBA surveyors. The approximate end of February 2012 water level (zero point) for the Lake Towerrinning Transect diagrams T1 – T13 in Appendix B was 218. 4 m AHD.



Figure 6: Land Unit Mapping - Lake Towerrinning Area

Source: Land Assessment Pty Ltd

Table 4: Land Unit Descriptions - Lake Towerrinning Area Land Unit

Description Land Unit

Description

Upland areas Wetlands and associated dunal terrain U Crests and upper slopes with mainly gravelly soils. W2 Outlet swamp Slopes – generally < 7% gradient W2a Winter-wet saline areas near W2 S1 Gravelly soils – moderately well drained Wf Wetland fringe areas with variable poorly drained

saline soils. S2 Deep sandy duplex soils – salt affected L1 Lunette – higher areas > 2 m relief Broad valley floor and alluvial flats L2 Lunette – lower areas F1 Deep sandy duplex soils (non-saline) D Undulating low-relief dunes or sandplain F2 Deep sandy duplex soils (potentially salt affected) Drainage pathways F3 Shallow duplex soils (saline) Dp1 Saline wet soils. R Elongated rise with red shallow loamy duplex soil Dp2 Shallow loamy duplex soils (salt affected). Wetlands and associated dunal terrain Dp3 Lesser pathways – variable soils; not always salt

affected. W1 Wetland – main body of Lake Towerrinning and

the connected Inlet Swamp.



3.3. Vegetation, Flora and Fauna

3.3.1. Overview

Vegetation Systems and Associations

Within the Jarrah Forest Biogeographic Region, Lake Towerrinning is in the 290,698 ha Beaufort Vegetation System, as shown in Figure 7.

Figure 7: Extent of the Beaufort Vegetation System Source: Shepherd, Beeston and Hopkins(2002) The Beaufort Vegetation System is generally dominated by Marri (Corymbia calophylla) and Wandoo (Eucalyptus wandoo) on undulating country, and Swamp Yate (Eucalyptus occidentalis) on clay valley floors (Beard, 1981). The extents of the vegetation associations in the vicinity of the lake are summarised in Table 5. Table 5: Extents of Vegetation Associations in Vicinity of Lake Towerrinning

Association Total Extent Extent Uncleared % Uncleared 4 Medium woodland; marri and wandoo 1,054,280 ha 317.912 ha 30.1 %

Source: Government of Western Australia (2009)



The vegetation system-associations (the combinations or intersections of vegetation systems and associations) that occur in the vicinity of the lake are shown in Figure 8.

Figure 8: Vegetation System-Associations in Vicinity of Lake Towerrinning Source: Shepherd, Beeston and Hopkins(2002)



The extents of the vegetation system-associations in the vicinity of the lake are summarised Table 6.

Table 6: Extents of Vegetation System-Associations in Vicinity of Lake Towerrinning System-Association Total Extent Extent Uncleared % Uncleared BEAUFORT_4.2 233,717 ha 48,420 ha 20.7 %

Source: Government of Western Australia (2009) Vegetation Complexes

The vegetation complexes occurring in the vicinity of the lake are shown in Figure 9.

Figure 9: Vegetation Complexes in Vicinity of Lake Towerrinning



The extents of the vegetation complexes in the vicinity of the lake are summarised Table 7. Table 7: Extents of Vegetation Complexes in Vicinity of Lake Towerrinning

Vegetation Complex Description Total

Extent Extent Uncleared

% Uncleared

Boscabel 1 Woodland of Wandoo-Jarrah on uplands 2,187 ha 149 ha 6.8 %

Darkin 1 Woodland of Jarrah-Wandoo-Marri over Parrotbush on uplands 1,8620 ha 2,697 ha 14.5 %

Darkin 2 Mixture of open woodland of Jarrah-Slender Banksia and low open woodland of Wandoo and stands of Drummond's Gum (northern) and Redheart (southern) on lower slopes

17,315 ha 1,227 ha 7.1 %

Darkin 3 Open woodland of Rock Sheoak-Jam with occassional Flooded Gum and Wandoo on variable slopes near granite outcrops and woodland of Brown Mallet-Wandoo on breakaways

7,289 ha 326 ha 4.5 %

Darkin 4 Woodland of Wandoo-Rock Sheoak-Jam on slopes and woodland of Flooded Gum on lower slopes over Parrotbush on uplands 9,037 ha 477 ha 5.3 %

Darkin 5 Low woodland of Saltwater Sheoak-Melaleuca species on low lying moister soils, and woodland of Acorn Banksia with occasional marri and Flooded Gum over Jam on sandy lunettes

4,901 ha 575 ha 11.7 %

Darkin 5f Woodland of Flooded Gum-Melaleuca species on lower slopes, low forest of Saltwater Sheoak and shrubland of melaleuca species on broad valley floors

5,780 ha 671 ha 11.6 %

Source: Bradshaw and Mattiske (1997) Havel (2002) identified the Boscabel 1 complex as falling below the 15% JANIS threshold for the adequate reservation of a complex (0% was recorded as reserved), largely as a result of it being outside of State forest, in the extensively cleared agricultural zone. Ecological Communities

No TECs (Threatened Ecological Communities) were recorded by the DEC within 15 km of the centre of Lake Towerrinning (DEC database search reference number 40-1211EC). One PEC (Priority Ecological Community) was recorded by the DEC within 15 km of the centre of Lake Towerrinning, this being the Priority 2 PEC: Blackwood Alluvial Flats of woodlands and shrublands of the alluvial soils of the upper Blackwood River (Condinup and Darkan 5f soil-landscape sub-systems). This PEC includes: Wet shrublands on alluvial clay flats Wandoo woodlands on grey sandy loams Jarrah-Marri woodlands on alluvial grey-brown loams Wandoo woodlands on alluvial grey-brown clay-loams (includes vernal pools) Flooded Gum-Wandoo woodland on alluvial grey clays (includes vernal pools).

Species Richness

The portion of the wheatbelt containing Lake Towerrinning was modelled as supporting more than 50% of the species in one terrestrial biodiversity assemblage that is low in the landscape (T27_33) by McKenzie, Gibson, Keighery & Rolfe (2004) and seven wetland biodiversity assemblages (W5, W6, W8, W13, W16, W17 and W18) by Halse, Lyons, Pinder & Sheil (2004), but Lake Towerrinning was not in, or near, a potential canditate recovery catchment identified by Walshe, Halse, McKenzie &



Gibson(2004) to optimise conservation of species (i.e. conserve a relatively large number of species through intensive management of a relatively small number of catchments). The flora richness in the locality of the Towerrinning Lake was modelled by CALM (1998) to be moderate, in the order of 200 to 300 species per square kilometre and the site in not in the vicinity of any areas identified by the Regional Forest Agreement Steering Committee(1998) as having potential national estate value based on high regional species or ecosystem richness. Flora

DEC’s incomplete flora inventories for Lake Towerrinning and Capercup Nature Reserve themselves consist of 36 and 97 species respectively (DEC, 2007)(Gibson, Keighery, Lyons, & Webb, 2004). The Threatened and Priority flora species recorded by the DEC within 15 km of the centre of Lake Towerrinning (DEC database search reference number 46-1211FL) are documented in Appendix E. Of these, the potential habitat onsite for the species associated with wetlands is discussed in Section 3.3.2. Fauna

As listed in Appendix C, the diversity of fauna in the locality of Lake Towerrinning is expected to consist of 1 fish, 14 frogs, 43 reptiles, 171 birds and 23 mammals (Bamford, 2012). Lake Towerrinning provides regionally significant habitat for birds: Towerrinning Lake is part of an Important Bird Area (IBA) identified by Birdlife Australia as

supporting up to 420 resident individuals from 1997-2007 (more than 1% of the global population) of the Blue-billed Duck Oxyura australis (Birdlife Australia, 2012). This species (which only occurs in Australia and is found particularly in the Murray-Darling basin and southern Victoria) has a stable and moderately small total population of 15,000 birds. Birdlife International (2012) identified this species as facing a number of threats, with a population that may be smaller than estimated. The Blue-billed Duck occupies permanent deep water-bodies and nests in rushes, sedges, and paperbark. Birdlife Australia (2012) suggested that salinisation, eutrophication and artificial deepening of Lake Towerrinning are likely to have a greater impact on the local population than water ski activities in demarcated areas.

Lake Towerrinning itself provides significant habitat for diving waterbirds in the form of extensive areas of deep (> 1 m deep) water of up to approximately 195 ha.

At times the lake supports regionally significant numbers of waterfowl. Numbers of waterfowl at Lake Towerrinning were in the top 15 of 1017 wetlands in south west Western Australia) in two of eight surveys between 1988 and 1992. The lake had the 11th highest number of waterfowl in March 1991 with 6984 birds and 12th highest in March 1992 with 3635 birds (Halse, Jaensch, Munro, & Pearson, 1990), (Halse S. , Vervest, Munro, Pearson, & Yung, 1992) ,(Halse, Pearson, Vervest, & Yung, 1995), (Halse, Vervest, Pearson, Yung, & Fuller, 1994)

Between 1981 and 1985, 14 of 36 bird species present breed onsite (Halse, Williams, Jaensch, & Lane, 1993).



The Threatened, Priority and Schedule fauna species recorded by the DEC within 15 km of the centre of Lake Towerrinning (DEC database search reference number Bennetts3962) are documented in Appendix C. Of these, the potential habitat onsite for the species associated with wetlands is discussed in Section 3.3.2.

3.3.2. Site Survey and Mapping Results Field reconnaissance for vegetation and flora was undertaken 14-16 February and 28 February, 2012. Vegetation - Towerrinning

Ten major vegetation formations (defined in terms of the dominant species in the dominant strata/layer) were identified in the immediate vicinity of Lake Towerrinning and these are shown in Figure 10.

Figure 10: Vegetation Formations in Vicinity of Lake Towerrinning All of the formations identified were associated with wetlands, except the woodlands dominated by Acorn Banksia (Banksia prionotes) Marri (Corymbia calophylla), Rock Sheoak (Allocasuarina huegeliana) and Wandoo (Eucalyptus wandoo). The vegetation fringing the lake is shown in transects in Appendix B. Along the periphery of the lake, there was a mixture of freshwater trees (e.g. Eucalyptus rudis, Melaleuca rhaphiophylla) and



saltwater tolerant trees (e.g. Melaleuca cuticularis, Casuarina obesa) that can also survive waterlogging with relatively fresh water (Carter, Colmer, & Veneklaas, 2006). Melaleuca cuticularis is also more tolerant of the combination of waterlogging and salinity than Casuarina obesa (Carter, Colmer, & Veneklaas, 2006). This intermingling of fresh and saltwater tree species was below the mapping threshold but indicates shallow groundwater seepage along parts of the lake, and the inlet and outlet swamps. Shallow groundwater seepage is also consistent with the extensive occurrence of Flooded Gum on slopes 10 m above the maximum level of the lake. The extent of sedgelands (totalling <1 ha) was below the mapping threshold, but occurrences of one species, Baumea articulata (which is a freshwater species and for which historical data was available) were noted. The occurrence of Baumea articulata sedgelands is likely to indicate shallow groundwater seepage along parts of the lake. There were historically extensive Baumea articulata sedgelands across Lake Towerrinning but these had contracted to several dozen small stands (1-4m2) by 1985 (Froend & McComb, 1991). The stands in the south and west portions of Lake Towerrinning appeared largely unchanged from that mapped in 1985. The two stands on the eastern shores of the lake appear to have been lost since 1985. None of the vegetation formations in vicinity appear to correspond with: the single TEC, Calothamnus graniticus heaths on south west coastal granites, endorsed by the

WA Minister for the Environment in the Jarrah bioregion (as at August 2010) any of the 24 PECs listed by DEC Species and Communities Branch as occurring in the Southwest

Region (as at 30 September 2011). The soil-landscape sub-systems in the immediate vicinity of the Towerrinning Lake are Darkan 5, Darkan 5w and Darkan 7, rather than Condinup and Darkan 5f which are associated with the nearest recorded PEC.

The vegetation formations mapped are within the range expected from the regional mapping of vegetation associations and vegetation complexes. Flora species richness in the immediate vicinity of Lake Towerrinning was relatively low. Much of the remnant vegetation consisted of trees, with little or no native shrubs, herbs, grasses or sedges. The areas of vegetation in best condition were: the woodland of Freshwater Paperbark on the sand spit between the inlet swamp and main lake the woodlands of Saltwater Sheoak and Freshwater Paperbark east of the outlet swamp.

Flora - Towerrinning

During the field survey 16 abundant, dominant and/or readily identifiable plant taxa were recorded in the immediate vicinity of the lake, taking the total flora inventory for the lake to 50 taxa (as listed in Appendix E). None of the species recorded onsite is listed as: Threatened Species under the Commonwealth EPBC Act 1999



Threatened Flora (T) in the Wildlife Conservation (Rare Flora) Notice 2011 under the Wildlife Conservation Act 1950

Priority Flora by DEC. There is a low likelihood of Threatened or Priority flora, which are associated with wetlands, occurring in the immediate vicinity of the Lake Towerrinning is low, as summarised in Table 8. Table 8: Likelihood of Significant Flora Occurring in Wetland Areas Around Lake Towerrinning

Taxa Status Lifeform Flowers Typical Habitat Likelihood of Detection

Likelihood of occurrence

Caladenia bryceana subsp. bryceana

T Perennial herb, 0.05-0.1 m high.

Aug to Oct.

Sand, loam. Adjacent to watercourses, winter-wet sites.

Low Possible - requires survey when flowering Aug to Oct

Grevillea elongata T Shrub,

1.5-2 m high. Oct.

Gravelly clay, sandy clay, sand. Road verges, swamps, creek banks

Medium

Very Low – No Grevillea shrubs (or similar) observed onsite had similar leaves

Ornduffia submersa P4 Perennial Herb

Aquatic

Not documented by DEC

Seasonal waterbodies Medium

Low – there was still water in parts of the lakes systems and it was absent from parts observed.

Eutaxia nanophylla P3 Shrub,

0.35 m high. Oct to Nov.

Clayey sand, red clay, stony clayey loam. Low-lying areas, damp flats, slopes, undulating plains, low stony ridges

Medium

Very Low - Most similar taxon onsite was Eutaxia ?empetrifolia (requires flowers or fruit to confirm but only likely alternative is Eutaxia parvifolia)

Stylidium lepidum P3 Perennial herb,

0.05 m high Oct to Nov.

Gravelly sand or loam, clay. Winter-wet depressions.

Low Possible - – requires survey when flowering Oct to Nov

Likelihood of Detection based on plant size, flowering and presence of features for ready field identification and life form.

High= Expected To Be Detected and Confirmed If Present Medium = Expected To Be Detected (but not necessarily confirmed, i.e. doubt may remain regarding identification) if Present Low = Unlikely to be Detected at time of Survey even if Present

Several flora populations onsite are close to the inland extents of species which are common further to the southwest (e.g. Club Rush Ficinia nodosa which was assumed to be naturally occurring, although this could was not confirmed) and Modong Melaleuca preissiana. Fauna - Towerrinning

Of the 252 vertebrate animals that Bamford (2012) identified as likely to occur in the locality of Lake Towerrinning, 14 are both listed as Threatened or Priority Fauna, and dependent and/or associated with wetlands (Appendix E). An indication of the relative importance of Lake Towerrinning to these species is provided in Table C1 of Appendix E. This table shows for each species, the distribution and abundance of the Australian population, the highest numbers recorded at the lake and comments on whether the species breeds in the wheatbelt and whether populations are increasing, stable or declining.



A fauna survey was not undertaken by Bamford Consulting Ecologists but on the basis of available literature, interpretation of vegetation (which was assessed in the field) as fauna habitat, and in consultation with Bamford Consulting Ecologists), the following comments to be made. Migratory shorebirds (Sandpiper species) and Eastern Great Egret have not been recorded in large numbers at Lake Towerrinning (Appendix E). However, the lake and the inlet and outlet swamps collectively provide some suitable habitat in the form of shoreline shallows, while the extensive (65 ha) areas of Samphire flats (herbland of Tecticornia species) and shallow (< 0.5 m deep) water (up to approximately 83 ha, and could be suitable habitat for some shorebirds. Peregrine Falcons were confirmed present at Lake Towerrinning in 2001 and 2006 (DEC Database Search Bennetts3962) and the abundance of waterbirds on the lake may provide a major food source at times. This raptor feeds almost entirely on other birds, although it also eats rabbits and other moderate sized mammals, bats and reptiles. Carnaby’s Black-Cockatoos may utilise the approximately 8 ha of Sheoak trees in the outlet swamp as a non-preferred/minor food source. The main food source is seeds from hakeas, grevilleas, banksias and eucalyptus). Nest hollows were not searched for, but there are likely to be few if any along a lake fringe dominated by Melaleuca cuticularis, Melaleuca rhaphiophylla, Eucalyptus rudis, Eucalyptus loxophleba (preferred trees are Eucalyptus wandoo which are upslope). Forest Red-tailed Black-Cockatoos may utilise the approximately 8 ha of Sheoak trees in the outlet swamp as a non-preferred/minor food source. The main food source for this bird is seeds from Marri (Corymbia calophylla). Nest hollows were not searched for, but there are likely to be few if any along a lake fringe dominated by Melaleuca cuticularis, Melaleuca rhaphiophylla, Eucalyptus rudis, Eucalyptus loxophleba (preferred trees are Corymbia calophylla and Eucalyptus marginata which are limited in number and upslope). Rakali (Water-Rat) may be in the locality of Lake Towerrinning but are unlikely to be in high abundance in the immediate vicinity of the lake. Direct evidence of their presence was not searched for, but the habitat requirements for Rakali include high vegetation and stream cover (important for avoiding predation), habitat diversity (potentially important for switching diet between seasons) and bank stability (for dens or burrows) (Smart, Speldewinde, & Mills, 2011). The extent of dense vegetation cover was limited in the vicinity of the lake, and the species has home ranges in the order of 0.9 km2 to 3.0 km2 (Smart, Speldewinde, & Mills, 2011). There may be individuals using part of the site as the species is able to travel long distances over dry land and individuals can access 3.9 km2 per night. This is more likely to the east of the lake, where remnant vegetation is more extensive and contiguous with the Arthur River. The Rufous Fieldwren has not been recorded at Lake Towerrinning (Appendix E). This species, if and when present, is more likely to reside in nearby samphire heaths and shrublands rather than the lake itself.



The Hooded Plover has not been recorded at Lake Towerrinning (Appendix E) and the relatively low salinity of the lake does not favour this species, which has a positive association with hypersaline conditions (Halse, Williams, Jaensch, & Lane, 1993) There may also be potential species of interest (though not necessarily Threatened or Priority) in sedgelands in the immediate vicinity of Lake Towerrinning (e.g. frogs). Vegetation – Capercup Nature Reserve

A cursory field inspection was undertaken of Capercup Nature Reserve but with no vegetation mapping. The major vegetation formations in Capercup Nature Reserve were: Woodland of Wandoo (Eucalyptus wandoo) with some Jarrah (Eucalyptus marginata) and

Redheart (Eucalyptus decipiens) Mallee of Drummond’s Gum (Eucalyptus drummondii) Mixed shrubland Sedgelands on Freshwater Seeps

The bushland condition was variable, ranging from Very Poor to Excellent. The species richness in Capercup Nature Reserve appeared moderate to high. Approximately 33 ha (or 20%) of the reserve has been degraded by secondary salinisation (as shown in Figure 11).

Figure 11: Extent of Secondary Salinisation within Capercup Nature Reserve



Flora – Capercup Nature Reserve

During the field survey 11 abundant, dominant and/or readily identifiable plant taxa were recorded, taking the total flora inventory to 108 (including the P4 Boronia tenuis), as listed in Appendix E. It is estimated that more than 200 plant species occur onsite.

Fauna – Capercup Nature Reserve

Forest Red-tailed Black-Cockatoos were observed opportunistically onsite. This is at the edge of the distribution range for the species (Bamford M. , 2012).

3.3.3. Factoring Influencing Approvals The requirement for, and/or level of a formal environmental impact assessments and approvals for Lake Towerrinning will likely involve consideration of: Vegetation Associations and Vegetation Complexes which are largely cleared. The EPA may

apply a presumption against any clearing (which includes draining and flooding, as well as direct clearing of land) in the vicinity of the lake as the portion remaining of Vegetation Association 4 is close to the 30% threshold, the portion remaining of Vegetation System-Association 4.2 is below the 30% threshold and the portion remaining of the Vegetation Complexes is below the 30% threshold, and for the Boscabel 1 complex that it is also not adequately reserved.

regionally significant habitat for waterfowl and the Blue-billed Duck potentially regionally significant habitat at times for migratory shorebirds (Sandpiper species),

and the Eastern Great Egret, and Rufous Fieldwren. The development of detailed engineering designs should include specific consideration of limiting impacts on: the often low level of fringing vegetation (littoral plants) with limited capacity to tolerate

salinity, or migrate upslope in response to a further increase in maximum lake levels including freshwater sedges around the main lake (Baumea articulata, Lepidosperma longitudinale and Juncus pallidus) and freshwater littoral trees around the main lake and outlet swamp (Eucalyptus rudis, Melaleuca rhaphiophylla and Melaleuca preissiana)

Salt/brackish littoral trees around the outlet swamp (Casuarina obesa and Melaleuca cuticularis)

the Peregrine Falcon, which could be indirectly impacted through changes in abundance of waterbirds

Carnaby’s Black-Cockatoo, which may utilise in Sheoak trees in the outlet swamp as a non-preferred/minor food source.

Forest Red-tailed Black-Cockatoo, which may utilise in Sheoak trees in the outlet swamp as a non-preferred/minor food source.



3.4. Aboriginal Heritage As shown in Figure 12, all of Lake Towerrinning (including the inlet and outlet swamps) is a registered Aboriginal Site (ID 964) and the cultural heritage values associated with this site are identified as ‘Ceremonial, Mythological’. Further details of this Registered Site are contained in Appendix D. There is also evidence of long-term Aboriginal use of the lake, particularly on the north shore (Shire of West Arthur 2008). DIA advise that; Lake Towerrinning is a place where traditional Aboriginal ceremony was practised and is associated with a sacred narrative. The site is described as ‘winnaitch’ (dangerous) due to events which occurred during the Dreaming at this place. It is also known as a place where corroborees used to be practised. As such it has previously been determined to be a place to which section 5(b) of the Aboriginal Heritage Act 1972 (AHA) applies. DIA is unaware of any Aboriginal heritage surveys which have been undertaken over the area of the Lake and there may be currently unrecorded Aboriginal heritage values which relate to the area of the Lake and its immediate surrounds. Also, as outlined in section 2.2.7; Lake Towerrinning is within the Gnaala Karla Booja native title claim area and a number of the claimants of this group are listed as primary site informants for this lake.

Figure 12: Registered Aboriginal Sites in Vicinity of Lake Towerrinning Source: On-line search of Aboriginal Heritage Inquiry System April 2012



3.5. Existing Lake Modifications and Initiatives In the early 1990’s the Lake Towerrinning Catchment Landcare Group (LTCLG) in conjunction with the then Department of Agriculture and the Water Authority of Western Australia (WAWA) undertook a hydrological assessment of the catchment. This led, in 1993, to the development of a stream re-diversion structure at the junction of the Morlup and Cordering Creeks with an associated 12 km waterway down to the lake. The aim of the re-diversion structure was to return the stream hydrology to its pre-1950 status and allow a greater volume of fresher quality water from the upper catchment area to drain towards the lake. The aim of the waterway was to improve the movement of that water towards the lake and to provide farmers with a method of draining land inundated in winter (George and Bennett 1992). At the southern end of the lake a spillway structure controls the maximum water level and allows flow from the lake into the ‘outlet swamp’ and from there eastwards to the Arthur River. By enabling lake flushing, the spillway is therefore one of the major means of manipulating the lake’s salt balance (George and Bennett 1992). At the time of the Landcare Group’s 1992 submission to the National Parks and Nature Conservation Authority for approval of the Cordering Creek re-diversion , the spillway level was established at the height of the lake’s average winter water level to allow for flushing and the establishment of a permanent water mark for fringing vegetation. This level was agreed to by the relevant State government agencies (now Department of Environment and Conservation, Department of Water, and Department of Agriculture and Food) as well as the Shire of West Arthur and adjoining landowners. The effect on Lake Towerrinning of the re-diversion structure and associated land management initiatives within the catchment is widely viewed as a success, with the Landcare Group (LTCLG) winning the State and National Landcare Australia Awards in 1994. In recent years however the poor water quality in the ‘outlet swamp’ to the south of the lake, and the effect of salinity on vegetation within Capercup Reserve to the lake’s northwest, have become matters of concern. In consideration of the history of natural resource management in the catchment, the focus of the Living Lakes Feasibility Study in relation to Lake Towerrinning has been to review and build upon the achievements of the Landcare Group and associated government agencies. Potential engineering options being considered are therefore aimed at ‘future proofing’ the lake and Capercup Reserve against future possible deterioration. A further matter that requires consideration is the viability of assuming effective on-going management of structures associated with maintaining the level and quality of water within the lake, when such structures are located on private land with only informal voluntary management arrangements in place.



3.6. Living Lake Enhancements – Environmental Considerations Seven enhancement options have been considered for Lake Towerrinning as part of the Living Lakes Feasibility Study. Although any recommended ‘hydrological solution’ to achieve the objectives of the Living Lakes initiative is likely to involve a combination of works in various areas, the individual enhancement options are outlined with relevant locations and site features shown in Figure 13.

Figure 13: Enhancements Considered in Living Lakes Project – Lake Towerrinning Source: Jim Davies and Associates

3.6.1. ET1: Increase Re-diversion Capacity (Extra Culvert) The objective of this enhancement option would be to enable more water to pass out of the Cordering Creek re-diversion structure and into the existing constructed 12 km waterway which leads down to the lake. This option offers the potential to increase the volume and longevity of water in the lake. The environmental considerations associated with this option are summarised as follows: The existing re-diversion structure has been designed to allow passage of relatively fresh winter

runoff towards the lake with the more saline early seasonal runoff directed towards Darlingup Creek.

Increased water flow through this structure could potentially deliver more salt to the lake if the

extra culvert allows passage of the higher salinity early seasonal runoff rather than its diversion



to Darlingup Creek. However this would be averted if the inlet level for the second culvert is set to the same level as the existing culvert.

Any significant increase in salinity within the lake (beyond a certain threshold) could change its

ecological status and lead to a less abundant waterbird fauna. Increased volume of flow out of the re-diversion structure has the potential to:

- require an increase to the size and capacity of channel to safely contain and convey water and avoid flooding adjacent farming land, and

- transport more silt down to the inlet swamp and lake as a result of channel scouring and bank erosion.

Risk Assessment - Low – assuming the existing maximum water level within the lake remains controlled at no higher than the current established level at the outlet structure (and hence no impact to the lake’s existing fringing vegetation from this additional water), and subject to adequate consideration of the design of the drainage channel in relation to increased water flow.

3.6.2. ET2: Capercup Reserve Drain To Lake By constructing a shallow drain to link Capercup reserve to the existing Cordering Creek drain (downstream from the re-diversion structure) the objective of this enhancement option would be to provide an additional source of water for the lake and, at the same time, to reduce the effects of a rising saline watertable on vegetation within the Capercup Nature Reserve. The environmental considerations associated with this option are summarised as follows: A shallow drain through the western portion of the Nature Reserve would improve vegetation

survival prospects by reducing the current extent and longevity of saline waterlogging. It would provide an additional source of water for the lake, although the extra amount is likely to

be relatively small with a shallow drain and limited catchment area. Saline surface water drainage directed from Capercup Reserve and into the Cordering Drain

would be diluted prior to lake entry as long as water in that drain emanating from the re-diversion structure continues to comprise relatively fresh winter catchment runoff.

Given the location of saline seepage areas upslope from the reserve, a ‘cut off’ drain around the

outside of the reserve has been considered but is impractical due to topography. Risk Assessment - Low – due to likely low volume of additional water and associated low salt load. Furthermore as a shallow surface drain, there would be no associated potential for an Acid Sulfate Soil issue.



3.6.3. ET3: Dredging of Lake (increased depth) The environmental considerations associated with this option are summarised as follows: In the absence of an additional source of water for the lake, dredging offers the potential for

greater depth and water longevity in some areas. If the excavated material was to be retained within the lake environment, an island could be

created for wildlife refuge.

Dredging may increase habitat (deep water) for diving waterfowl but reduce the extent and duration of shallow water for shorebirds if the existing shoreline area is altered.

On the basis of limited sampling of lake bed and fringing soils, the potential for acid sulfate soil

problems arising from exposure of dredged sediment to air is considered unlikely.

As a permanent lake, any ‘wet-dredging’ activity would incur a risk of water quality impacts due to re-suspension of sediment and nutrients and, although likely to be temporary, this could adversely affect waterbird fauna and the hydrochemistry of the lake.

Removal of lake-bed sediment (and associated seed banks) would deplete food sources for the

lake’s invertebrates and waterbirds in affected areas, and risk reducing the biological productivity of the lake.

Aboriginal cultural heritage values are assigned to all portions of the lake, and an enhancement option involving dredging is considered most likely to be an unacceptable impact in this regard.

Risk Assessment - High – due to the likely unacceptability of lake-bed disturbance on Aboriginal cultural heritage values, the status of the lake as a Nature Reserve for purposes including protecting waterbird habitat, and uncertainty relating to potential impacts on benthic habitat and nutrient remobilisation.

3.6.4. ET4: Groundwater Replenishment This enhancement option involves providing an additional source of water to ‘top up’ the lake using groundwater bores sunk into a nearby palaeochannel. The environmental considerations associated with this option are summarised as follows: As with other water addition options, there would need to be a consideration of the effects of

any resulting change to the salinity of the lake, and any increase in the lake’s maximum water level which could adversely affect fringing vegetation.



Risk Assessment - Low –assuming availability of groundwater of suitable quantity and quality, and that existing maximum water level within the lake remains controlled at no higher than the current established level at the outlet structure (and hence no impact to the lake’s existing fringing vegetation from this additional water). Note: JDA advise that given the availability of surface water resources associated with the re-diversion structure and its drainage channel, the option of exploiting palaeochannel resources has not been further investigated as part of the Feasibility Study at Lake Towerrinning.

3.6.5. ET5: Rehabilitation Re-diversion Drain The objective of this enhancement option would be to increase the amount of water that ultimately reaches the lake after entering the drainage channel downstream from the re-diversion structure. It would involve cleaning out sediment, re-profiling the drain, cleaning out culverts and silt traps, and removing any vegetation obstructing water flow. The environmental considerations associated with this option are summarised as follows: In conjunction with the Cordering Creek re-diversion structure, on-going maintenance of its

downstream drain was identified as an important component of the Catchment Group’s plan (LTCLG 1992) to improve Lake Towerrinning.

Complimentary land management actions such as avoiding overstocking and strategic

revegetation within parts of the catchment’s farmland should help to reduce sediment input. In many areas the design of the drain allows stock access and movement from one side to the

other so that farming is not impeded in paddocks containing drains. Sediment build up has occurred in portions of the drain, and this is likely to result in less water

reaching the lake due to pooling and subsequent losses through evaporation, and to increases the risk of localised flooding of adjacent farmland.

The existing silt fan within the inlet swamp is a result of erosion and sediment transport down the drainage pathway, but it also plays important role as a trap for nutrients attached to sediment, and provides a suitably shallow habitat for wading waterbirds.

In light of the above it is suggested that drain rehabilitation activities are confined to the largely

‘man-made’ portions of the drainage pathway and do not affect the silt fan within the inlet swamp.

Risk Assessment - Low – subject to retaining the silt fan at the lower end of the drain, and consideration of the effect of any modifications on flood risk to adjacent areas as well as the efficiency of water conveyance.



3.6.6. ET6: Refine Drainage from Outlet Swamp to Arthur River This enhancement option involves improving drainage flow from the ‘outlet swamp’ down to the Arthur River. The objective would be to facilitate increased flushing of the total wetland system to improve water quality in both the outlet swamp and Lake Towerrinning. The environmental considerations associated with this option are summarised as follows: In conjunction with the Cordering Creek re-diversion structure, effective flushing of the lake all

the way through to the Arthur River was identified as an important component of the Catchment Group’s plan (LTCLG 1992) to improve Lake Towerrinning.

Site observations indicate the connection between the outlet swamp and Arthur River is not

always functional, and in many years through-flow has been restricted by higher terrain near the eastern end of the outlet swamp.

Water trapped in outlet swamp becomes increasingly saline as a result of evaporation and the

associated vegetation has become degraded. Improving drainage flow from the ‘outlet swamp’ down to the Arthur River would enable more

regular flushing and improve quality of water in outlet swamp. Less saline conditions in the outlet swamp could support a more abundant waterbird fauna.

As shown in Figure 6: and Figure 10 the existing topography suggests two alternative routes for

works to improve drainage outflow, both of which involve some potential impact on native vegetation but not affecting any threatened or priority ecological communities or flora species.

The southern drainage route contains a smaller extent of native vegetation in good condition and

hence is the preferred route. The capacity of drainage culverts beneath Darkan Road South would need to be assessed to

ensure no increased risk of flooding resulting from implementation of this enhancement option. Aboriginal cultural heritage values are assigned to all portions of Lake Towerrinning including the

outlet swamp, and an enhancement option involving drainage may be considered to be an unacceptable impact to those cultural values.

Risk Assessment - Low – assuming that some water remains for semi-regular inundation of the outlet swamp and hence maintenance of biological and cultural heritage values.



3.6.7. ET7: Modify Outlet Structure from Lake to Outlet Swamp This enhancement option would seek to improve the existing outlet structure on the southern side of the lake to enable easier operation and monitoring of releases which ultimately control its water level and flushing. The environmental considerations associated with this option are summarised as follows: The existing overflow level at this structure was established to allow for flushing and a permanent

high water mark for fringing vegetation – a level agreed to by agencies, the Shire and adjoining landholders (Refer Submission to the National Parks and Nature Conservation Authority - LTCLG 1992)

Any increase to the water level above the lake’s existing maximum needs to consider:

- the narrow extent of fringing vegetation around parts of the lake where there is limited ability for vegetation to adapt to higher water levels,

- the potential for flooding and decreased productivity on nearby farmland flats, - the potential for reduced access across the landholding on the western side of lake; and - the possible adverse effect of a higher underlying water-table on Lakeside Camping’s on-site

effluent disposal system within the lower lunette landform (L2 – Figure 6: ). The use of boards within the existing structure to control the level of water has been problematic

and for safety reasons a mechanism that doesn’t involve someone to physically enter the water to remove boards is preferred.

Formal monitoring of water levels and water quality (perhaps using an automated system) could provide data to better inform decisions related to water releases for flushing of both the lake and the outlet swamp.

Risk Assessment - Nil to High – Nil risk assumes the existing maximum water level within the lake remains controlled at no higher than the current established level at the outlet structure (and hence no impact to the lake’s existing fringing vegetation). High risk assumes a higher setting of the overflow level, resulting in a significant increase in the duration of inundation for the lake’s existing fringing vegetation.



4. LAKE EWLYAMARTUP

4.1. Lake Values and Catchment Context Lake Ewlyamartup, located approximately 17km east of Katanning, is an ephemeral saline wetland with an area of approximately 88 ha. The lake forms part of the ‘Ewlyamartup Lakes Wetland Group’ with identified environmental values relating to its faunal populations, wildlife sanctuary, and habitat linkage (Pen 1997). Although the Ewlyamartup wetland group is not a Ramsar wetland and is not listed in the Directory of Important Wetlands in Australia (Environment Australia 2001) it is recognised as regionally significant within the South West Regional Strategy for Natural Resource Management (South West Catchments Council 2004, 2005). Lake Ewlyamartup has a history of recreational use and value to the Katanning community, and is currently the subject of a lake restoration initiative, independent of the Living Lakes Project. The local community project is directed by the Lake Ewlyamartup Working Group (LEWG) established under the auspices of the Katanning Land Conservation District Committee. The Group has made considerable progress in developing an engineering concept plan (LEWG 2010) as part of a ‘whole of catchment’ approach to restoring the lake, and that work is a key component of the reference material for the Feasibility Study. Lake Ewlyamartup is contained within C Class Reserve No 16358 (Figure 14). The Department of Regional Development and Lands (RDL) is the responsible agency and the reserve is managed by the Shire of Katanning for the purposes of ‘Recreation’.



Figure 14: Lake Ewlyamartup – Aerial Image and Cadastre Data Source: Background - Landgate Map Viewer - online image - accessed Sep 2011 The Lake Ewlyamartup catchment extends over approximately 50,700 ha in the central part of the Shire of Katanning and contains three distinct sub-catchments – Katanning Creek, Murdong Pools and North Ewlyamartup (Figure 15). Lake Ewlyamartup is described by LEWG (2010) as a terminal lake, having a single inlet and outlet point on its northern side adjacent to the Katanning –Nyabing Road. The lake is fed by Ewlyamartup Creek and once the lake is full, water bypasses the entry point and continues in a north easterly direction for about 2.5 km until it reaches the Coblinine River. The Coblinine River then drains to north and north-west within very broad flat-floored valley up to Lake Dumbleyung in the central portion of the upper catchment of the Blackwood River. Coblinine River is partly encompassed within Coblinine Nature Reserve (No 25136) which is an A Class reserve vested with the Conservation Commission and managed by DEC for the purpose of Conservation of Flora and Fauna.

Unclassified Crown Land (RDL)

Reserve 10443 (RDL)

Reserve 16538 (Shire)

Katanning – Nyabing Road



Figure 15: Lake Ewlyamartup Catchment Source: Adapted from Lake Ewlyamartup Working Group (2010)


4.2.1. Overview The Department of Agriculture and Food’s broad-scale soil-landscape mapping over the south west agricultural area (http://spatial.agric.wa.gov.au/slip) provides an initial framework for consideration of the Lake Ewlyamartup environment.



Soil landscape systems are defined as ‘areas with recurring patterns of landforms, soils and vegetation’ (Schoknect et al., 2004). The study area consists of two soil landscape systems: Coblinine System: Broad (1-7 km), level to very gently inclined alluvial plains and lacustrine

plains with small areas of lunettes and sandplain along the Coblinine River and its tributaries. Mainly saline wet soils with alkaline grey shallow sandy and loamy duplex soils and grey deep sandy duplex soils.

East Katanning System: Gently undulating to undulating rises. Mainly sandy gravels with grey shallow and deep sandy duplex soils, including soils with alkaline subsoils.

These systems are divided in the Ewlyamartup locality into a number of subsystems and phases as shown in Figure 16 with associated Table 9 providing a description of relevant mapping units. Lake Ewlyamartup forms part of a flat sediment filled landscape with complex drainage systems where there is much potential to retain sediments and nutrients rather than transport them downstream. In such a landscape floodwaters are dispersed very slowly. The floodplain downstream from Lake Ewlyamartup is broad and generally poorly defined, with significant areas of salt affected land. Table 9: Soil Landscape Map Units - Lake Ewlyamartup Area

Soil landscape Map Units Description (dominant soils and landform) Coblinine System: (Cb) Broad alluvial plains and lacustrine plains. Mainly saline wet soils.

Cb2 Plains and stream channels. Saline wet soils, many grey shallow sandy duplex soils. Cb3 Plains and stream channels. Saline wet soils, minor sandy duplex and grey clays. Cb4 Lakes, swamps, lunettes swamps and dunes (1 – 5 m relief). Cb5 Lunettes, dunes and swales (2 – 20 m relief). Cb6 Sandplain and dunes. Mainly deep sandy duplex soils.

East Katanning System: (Ek) Gently undulating rises and rare low hills. Mainly sandy gravel soils. Ek1 Mid to upper slopes. Gravelly soils. Ek2 Lower to upper slopes. Sandy duplex soils. Ek4 Valley flats. Saline wet soils.

Source: Percy, H.M. (2000). Katanning Area Land Resources Survey, Land Resources Series No. 16, Department of Agriculture, Perth.



Figure 16: Soil-Landscapes - Lake Ewlyamartup Source: Background – Department of Agriculture and Food - Soil landscape systems (Percy 2000) accessed via Landgate Shared Land Information Platform (SLIP).



4.2.2. Site Survey and Mapping Results Given the broad scale of soil landscape mapping shown in Figure 16, some ‘on-ground’ variation can be expected in soil and landform conditions. More detailed mapping of the component ‘land units’ (landform soil types) was therefore undertaken by Land Assessment Pty Ltd in late February 2012 as a basis for understanding the local environmental setting and the possible implications of lake enhancement options. Soil and landform conditions were examined through aerial photo interpretation and a subsequent 3 – 4 day field survey period during which soils were described at 32 geo-referenced ‘hand auger’ sites associated with, but not limited to, a lesser number of lake margin transects as shown in Figure 17. At each observation site, soils were classified in accordance with the Department of Agriculture and Food’s WA Soil Group nomenclature (Schoknecht 2002) and the landforms described according to its Land Evaluation Standards (van Gool et al 2005). Representative soil samples were obtained from a number of sites for subsequent analysis of soil pH and salinity. Appendix A provides site summaries and associated data from the field survey work. The resulting land unit mapping for Lake Ewlyamartup is shown in Figure 18 and described in Table 10. Although site numbers were not sufficient to fully characterise soil conditions, the resulting mapping nevertheless provides significantly more detail than the existing published soil landscape mapping. In conjunction with the detailed vegetation mapping by Woodgis Environmental Assessment & Management, the land unit mapping provides an appropriate framework for consideration of areas around the lake where impacts may arise from any future changes to local hydrological conditions following implementation of ‘enhancement options’. Further detail of landform, soil and vegetation inter-relationships is provided within lake margin cross-section transect diagrams E1 – E6 contained in Appendix B. Transect diagrams were produced from field measurements involving a digital laser rangefinder, clinometer, staff gauge and measuring tape. Transect diagrams in Appendix B start (zero point), where possible, at water level at the time of field work. Actual water level at that time, in metres AHD, has been determined by correlation to reference points (such as staff gauges) that were subsequently surveyed by JBA surveyors. The approximate end of February 2012 water level (zero point) for the Lake Ewlyamartup Transect diagrams E1 – E6 in Appendix B was 272.6 m AHD.



Figure 17: Location of Soil Sites and Transects – Lake Ewlyamartup



Figure 18: Land Mapping Unit - Lake Ewlyamartup Area Source: Land Assessment Pty Ltd Table 10: Land Unit Descriptions - Lake Ewlyamartup Land Unit


Description

Upland areas Broad valley floor and alluvial flats

U1 Deep sandy duplex soils (non-saline) Fd Drainage pathways – distinct U1s Narrow fringing sandy slopes Fd1 Drainage pathways - indistinct U2 Gravelly soils Wetlands and associated terrain U2s Narrow steep breakaways W1 Wetland – main body of Lake Ewlyamartup Broad valley floor and alluvial flats W2 Entrance channel and adjacent ‘backwater’ F1 Deep sandy duplex soils (non-saline) W2a Winter-wet saline areas near W2 F2 Deep sandy duplex soils (saline) Sf Samphire fringes of lake or nearby depressions. F3 Shallow duplex soils (saline) Dp Drainage pathways with saline wet soils. 3a – sandy duplex; 3b - loamy duplex L Lunette – L1 higher areas > 2 m relief; L2 – lower F4 Grey clays – winter wet D Undulating low-relief dunes or sandplain




4.3.1. Overview Vegetation Systems and Associations Within the Avon Wheatbelt Biogeographic Region, Lake Ewlyamartup is in the 378,612 ha Dumbleyung Vegetation System, as shown in Figure 19.

Figure 19: Extent of the Dumbleyung Vegetation System Source: Shepherd, Beeston and Hopkins(2002) The Dumbleyung Vegetation System is generally gently undulating with scattered laterite cappings (especially in the north), and salt-flats and lakes occupying the principal valleys, sometimes with associated sand deposits (Beard, 1981). The gently undulating terrain principally supports woodlands of York Gum, Red Morrel, Salmon Gum and Wandoo; the salt-flats supports mallees, teatree and samphire; and the low-level sandplains support low woodlands (Beard, 1981). The adjacent systems to the west differ in that:

the Wagin System receives higher rainfall, and is more undulating and dissected the Broomehill System is an almost flat plateau of winter-wet heavy soils.



The extent of the vegetation association encompassing the lake is summarised in Table 11. Table 11: Extent of Vegetation Associations in Vicinity of Lake Ewlyamartup

Association Pre-European Extent

Current Extent % Remaining

1085 Succulent steppe with open woodland & scrub; Wandoo, Salmon Gum & Saltwater Sheoak over teatree & samphire 51,787 ha 7,943 ha 15.3 %

125 Bare areas; salt lakes 3,489,858 ha 3,278,701 ha 94.0 %

1092 Medium woodland; Wandoo, York Gum & Morrell 77,951 ha 8,232 ha 10.6 % 1023 Medium woodland; York Gum, Wandoo & Salmon Gum 1,601,601 ha 175,748 ha 11.0 % 1087 Medium woodland; Wandoo, Morrell & Blue Mallet 753 ha 257 ha 34.1 %

Source: Government of Western Australia (2009) The vegetation system-associations occurring in the vicinity of the lake are shown in Figure 20.



Figure 20: Vegetation System-Associations in Vicinity of Lake Ewlyamartup Source: Shepherd, Beeston and Hopkins(2002) The extents of the vegetation system-associations occurring in the vicinity of the lake are summarised in Table 12.



Table 12: Extents of System-Associations in Vicinity of Lake Ewlyamartup

Association Pre-European Extent Current Extent % Remaining

BROOMEHILL_1085 51,787 ha 7,942 ha 15.3 % DUMBLEYUNG_125 7,018 ha 592 ha 8.4% DUMBLEYUNG_1092 77,951 ha 8,231 ha 10.6% WAGIN_1023 115,018 ha 17,352 ha 15.1% WAGIN_1087 619 ha 187 ha 30.2%

Source: Government of Western Australia (2009) Ecological Communities

No TECs and no PECs were recorded by the DEC within 15 km of the centre of Lake Ewlyamartup (DEC database search reference number 40-1211EC). Species Richness

The portion of the wheatbelt containing Lake Ewlyamartup was modelled as supporting more than 50% of the species in two terrestrial biodiversity assemblages (T6 and T27_33) low in the landscape by McKenzie, Gibson, Keighery & Rolfe (2004) and four wetland biodiversity assemblages (W5, W6, W8 and W13) by Halse, Lyons, Pinder & Sheil(2004). Lake Ewlyamartup catchment is contiguous with the potential canditate Blackwood Recovery Catchment identified by Walshe, Halse, McKenzie & Gibson(2004) to optimise conservation of species (i.e. conserve a relatively large number of species through intensive management of a relatively small number of catchments). The Blackwood Recovery Catchment (centred on Lake Coyrecup) was identified by Walshe, Halse, McKenzie, & Gibson(2004) as potentially significantly contribute to the preservation of the following three biodiversity assemblages of:

Terrestrial Assemblage T6,which consists of 112 species associated with poorly drained soils of moderate to high salinity that previously supported woodlands or cheopod shrublands (with a sub-group associated with freshwater communities that occur at the periperhy of saline areas);

Terrestrial Assemblage T27_33, which consists of 239 species that are centered on broad valley floors and associated with poorly drained soils of low salinity; and

Wetland Assemblage W1, which consists of 27 species mostly associated with freshwater and centred in the central and southern wheatbelt.

Flora

DEC’s incomplete flora inventory for the immediate surrounds of Lake Ewlyamartup consists of one species (DEC, 2007)(Gibson, Keighery, Lyons, & Webb, 2004). The Threatened and Priority flora species recorded by the DEC within 15 km of the centre of Lake Ewlyamartup (DEC database search reference number 46-1211FL) are documented in Appendix E. Of these, the potential habitat onsite for the two Priority flora taxa that are associated with wetlands is discussed in Section 43.3.2.



Fauna

As listed in Appendix C the diversity of fauna in the locality of Lake Ewlyamartup is expected to consist of 8 frogs, 42 reptiles, 175 birds and 26 mammals (Bamford, 2012). Lake Ewlyamartup is not listed as an Important Bird Area (Birdlife Australia, 2012) although on limited occasions the lake has supported very high numbers of waterbirds. It can provide significant suitable habitat for diving waterbirds in the form of extensive areas of deep (>1 m deep) water of up to approximately 106 ha. At times the lake supports regionally significant numbers of waterfowl and in March 1992, Lake Ewlyamartup had the 14th highest recorded number of waterfowl (3,055 birds) in SW WA (Halse, Pearson, Vervest, & Yung, 1995). A wetland typically supporting low numbers of birds can occasionally act as a drought refuge, supporting large numbers of birds, due to high rainfall in the locality compared to the region. The value of an individual wetland as a drought refuge is magnified when there are few nearby wetlands (i.e. that are typically subject to the same local rainfall events). Lake Ewlyamartup is not an isolated wetland. Nearby wetlands include Lake Coyrecup, approximately 9 km east, which consistently supports higher numbers of birds. In March 1992 when Lake Ewlyamartup had the 14th highest recorded number of waterfowl (3,055 birds) in SW WA, Lake Coyrecup supported 13,493 birds (Halse, Pearson, Vervest, & Yung, 1995). The Threatened, Priority and Schedule fauna species recorded by the DEC within 15 km of the centre of Lake Ewlyamartup (DEC database search reference number Bennetts3961) are documented in Appendix C. Of these, the potential habitat onsite for the species associated with wetlands is discussed in Section 3.3.2.

4.3.2. Site Survey and Mapping Results Vegetation Field reconnaissance for vegetation and flora was undertaken 17 February and 29 February, 2012. Eleven major vegetation formations (defined in terms of the dominant species in the dominant strata/layer) were identified in the immediate vicinity of Lake Ewlyamartup, and these are shown in Figure 21.



Figure 21: Vegetation Formations in Vicinity of Lake Ewlyamartup The vegetation emanating out from the lake is shown in transects in Appendix B. The condition of the littoral trees (which are generally Casuarina obesa) appears to be also declining due to waterlogging and/or wave action causing erosion around their roots. Anecdotal information was supplied that suggested this erosion was caused by wind-driven waves rather than powerboat caused waves. Comparison of a wind rose, with a map of undercut shorelines could shed light on the likely cause. These woodlands appear to have been protected from secondary salinisation, inundation and highly alkaline water by the Katanning-Nyabing Road, which has restricted flow of surface waters into the area. The water in Lake Ewlyamartup at times is highly alkaline and Eucalyptus occidentalis and Eucalyptus spathulata are both relatively sensitive to alkalinity, with survival rates of 16.7% and 20.0% respectively at a pH of 8.0, relative to Casuarina obesa and Eucalyptus loxophleba, with survival rates of 38.0% and 91.7% respectively at this pH (Bell, Wilkins, van der Moezel, & Ward, 1993).



None of the ecological communities in vicinity appear to correspond with the 12 TECs endorsed by the WA Minister for the Environment in the Avon-Wheatbelt bioregion (as at August 2010). The ecological communities to the east of lunette on the eastern shore of Lake Ewlyamartup may correspond to 1 of the 21 PECs listed by DEC Species and Communities Branch as occurring in the Wheatbelt Region (as at 30 September 2011). Approximately 50 ha of woodland appears to fall under the broad definition of the PEC ‘Eucalypt woodlands of the Western Australian Wheatbelt’ in Good or better condition. The definition of this recently listed PEC is likely to be subject to refinement as data are collated on potential occurrences. DEC has been supplied details of sites to determine if areas should be considered occurrences of the PEC. The vegetation formations mapped are within the range expected from the regional mapping of vegetation associations and vegetation complexes. Species Richness The species richness in the survey area appeared moderate and bushland condition variable: the periphery of the lake was degraded due to clearing and secondary salinisation the vegetation north of the Katanning-Nyabing Road (north of the lake) was largely degraded

due to secondary salinisation the lunette on the eastern shore of Lake Ewlyamartup appeared to have been degraded by

historic grazing and/or fire and a woodland of Rock Sheoak over exotic grasses may have displaced a woodland of Acorn Banksia Banksia prionotes (of which small Very Poor condition remnants remain onsite)

the eucalypt woodlands (of Eucalyptus occidentalis, Eucalyptus spathulata, Eucalyptus wandoo) to the east of the lunette were relatively intact compared to the rest of the survey area.

Walshe, Halse, McKenzie, & Gibson (2004) identified the locality as potentially significant for the preservation of three biodiversity assemblages: Terrestrial Assemblage T27_33 may be well represented in the woodlands to the east Lake

Ewlyamartup. Many of the plants in the assemblage are herbaceous (and only readily detected during a spring survey) but some of the trees in the assemblage are present onsite (including Eucalyptus wandoo, Eucalyptus occidentalis and Allocasuarina huegeliana).

Terrestrial Assemblage T6 may be well represented to the north of Lake Ewlyamartup, as the assemblage consists of species associated with poorly drained soils of moderate to high salinity that previously supported woodlands or chenopod shrublands. However this assemblage is associated with secondary salinisation, and therefore not requiring active management for conservation values.

Wetland Assemblage W1 is not expected to be well represented in the immediate vicinity of Lake Ewlyamartup, as the species the assemblage consists of are mostly associated with freshwater.



Flora During the field survey 18 taxa abundant, dominant and/or readily identifiable plant taxa were recorded in the immediate vicinity of the lake, taking the total flora inventory to 19 taxa (as listed in Appendix E). None of the species recorded onsite was listed as: Threatened Species under the Commonwealth EPBC Act 1999 Threatened Flora (T) in the Wildlife Conservation (Rare Flora) Notice 2011 under the Wildlife

Conservation Act 1950 Priority Flora by DEC

There is a high likelihood of one Priority flora occurring in the immediate vicinity of the Lake Ewlyamartup, as summarised in Table 13. Table 13: Likelihood of Significant Flora Occurring in Wetland Areas Around Lake Ewlyamartup

Taxa Status Lifeform Flowers Typical Habitat

Likelihood of Detection


Melaleuca pritzelii 3 Shrub,

0.7-1.6 m high.

Aug to Oct or Dec.

Sandy or clayey soils. Swampy areas

Medium High – Plant previously recorded in vicinity

Verticordia huegelii var. tridens

3 Shrub, 0.15-0.6 m high.

Sep to Nov.

Sandy or gravelly loam. Winter-wet areas, low hills.

Medium Very Low – No Verticordia species seen in the vicinity

Likelihood of Detection based on plant size, flowering and presence of features for ready field identification and life form. High= Expected to Be Detected and Confirmed If Present Medium = Expected to Be Detected (but not necessarily confirmed, i.e. doubt may remain regarding identification) if Present Low = Unlikely to be Detected at time of Survey even if Present The two previously recorded populations of Melaleuca pritzelii closest to Lake Ewlyamartup were visited during the field reconnaissance, but no plants were located. This may have been due to imprecise location details (which is not unusual for records pre-dating the current precision of GPS units), but the immediate surrounds of one site is now hypersaline and if the location details were precise then this population may now be extinct. There may also be relatively few Melaleuca pritzelii shrubs occurring in the vicinity of Lake Ewlyamartup. No records of numbers of plants in the vicinity could be obtained from DEC, but despite there being 42 records of Melaleuca pritzelii between Jerramungup and West Arthur (DEC, 2007) many occurrences of this Melaleuca pritzelii consist of only a few plants (Quinn, Crowley, Barlow, & Thiele, 1998). Several flora populations onsite are close to the inland extents of species which are common further to the south-west (e.g. Acorn Banksia Banksia prionotes).



Fauna Of the 251 vertebrate animals that Bamford (2012) identified as likely to occur in the locality of Lake Ewlyamartup, 12 are both listed as Threatened or Priority Fauna, and dependent and/or associated with wetlands (Appendix C). An indication of the relative importance of Lake Ewlyamartup to these species is provided in Table C1 of Appendix E. This table shows for each species, the distribution and abundance of the Australian population, the highest numbers recorded at the lake and comments on whether the species breeds in the wheatbelt and whether populations are increasing, stable or declining. A fauna survey was not undertaken by Bamford Consulting Ecologists but on the basis of available literature, interpretation of vegetation (which was assessed in the field) as fauna habitat, and in consultation with Bamford Consulting Ecologists), the following comments to be made. The Eastern Great Egret and migratory shorebirds (including the six Sandpiper species listed by Bamford (2012)) may have not been recorded in large numbers at Lake Ewlyamartup (Appendix E) but the lake provides significant suitable habitat in the form of extensive areas of shallow (< 0.5 m deep) water of up to approximately 75 ha. There are also extensive areas of Samphire flats (herbland of Tecticornia species) to the north of the lake extending into and through the Coblinine Nature Reserve up to approximately hundreds of hectares. The Rufous Fieldwren has not been recorded at Lake Ewlyamartup (Appendix E). This species is more likely to be present in vicinity in samphire heaths and shrublands (which are extensive) to the north of the Katanning-Nyabing Road rather than the lake itself. Peregrine Falcons were recorded in the locality 2000-2002 (DEC database search reference numbersBennetts3961) and may at times use the abundance of waterbirds on Lake Ewlyamartup as a major food source. This raptor feeds almost entirely on other birds, although it also eats rabbits and other moderate sized mammals, bats and reptiles. Carnaby’s Black-Cockatoos in the locality may utilize the approximately 31 ha of Rock Sheoak trees on the lunette on the eastern shore as a non-preferred/minor food source. Their main food source is seeds from hakeas, grevilleas, banksias and eucalyptus. Nest hollows were not searched for, but there are likely to be few if any along a lake fringe dominated by Casuarina obesa (preferred trees are Eucalyptus wandoo which are to the east of the lunette of Rock Sheoak trees).There are approximately 20 breeding pairs of the Carnaby's Black-Cockatoo in the Kwobrup-Badgebup wetlands, approximately 18 km north-east (Birdlife Australia, 2012). The Priority 4 Hooded Plover breeds at Lake Ewlyamartup and up to 10 individuals have been recorded (see Appendix E). The site characteristics that favour this bird include: high salinity – the species has a positive association with hypersaline conditions (Halse, Williams,

Jaensch, & Lane, 1993)



relative complexity of the shoreline which assists in camouflage and protection of nests(Bamford M. , 2012)

4.3.3. Factoring Influencing Approvals The requirement for, and/or level of a formal environmental impact assessments and approvals for Lake Ewlyamartup will likely involve consideration of: the Vegetation Associations and Vegetation Complexes are largely cleared. The EPA may apply a

presumption against any clearing (which includes draining and flooding, as well as direct clearing of land) in the vicinity of the lake as the portion remaining of most of the Vegetation Associations and Vegetation System-Associations are below the 30% threshold

regionally significant habitat for moderate numbers waterfowl and low numbers of Hooded Plover

potentially regionally significant habitat at times for migratory shorebirds (Sandpiper species), and the Eastern Great Egret, and Rufous Fieldwren

the entirety of Lake Ewlyamartup is a registered Aboriginal Site. The development of detailed engineering designs should include specific consideration of limiting impacts on: the Priority 3 shrub, Melaleuca pritzelii that occurs in the vicinity of Lake Ewlyamartup, but

possibly in small numbers the eucalypt woodlands (which are a potential PEC) that may be susceptible to saline and/or

alkaline water overflowing out any channels constructed through them littoral trees that are being destabilised due to waterlogging and/or wave action causing erosion

around their roots, as this could be exacerbated by maintaining waterlevels at higher levels for longer durations

any areas supporting live trees north of the Katanning-Nyabing Road in terms of direct clearing.

4.4. Aboriginal Heritage Research conducted by the Lake Ewlyamartup Working Group prior to the Living Lakes Feasibility study showed three listed sites of Aboriginal Heritage at Ewlyamartup (Figure 22). Within the Unallocated Crown Land to the north-east, there is a broad area of artefacts and scatter remains. On the south-east bank of the Lake, there is a burial site and an artefacts site. The two sites adjacent to the Lake are on the permanent register (DIA, 2010).



Figure 22: Lake Ewlyamartup – Registered Aboriginal Sites (as at September 2010) Source: On-line search of Aboriginal Heritage Inquiry System September 2010 More recently, in November 2011, the Katanning LCDC (on behalf of LEWG) submitted an application under Regulation 10 of the Aboriginal Heritage Act seeking approval for works proposed under the Restoring Lake Ewlyamartup initiative (LEWG 2010). An Aboriginal Heritage assessment was then undertaken by the DIA (Davis and McGann 2011) and recommended classification of whole of lake and adjacent reserves south of Katanning-Nyabing Road as an aboriginal site. This recommendation has subsequently been implemented (Figure 23) and the cultural heritage values associated with this site (ID 4541) are identified as ‘Mythological, Skeletal material/ Burial Quarry, Artefacts/ Scatter, Historical’ (Appendix D). DIA have provided further clarification that; Lake Ewlyamartup is known to have large amounts of archaeological material associated with traditional Aboriginal life surrounding it; this includes areas where the material is beneath the current surface of the land. Further, there are oral records of an Aboriginal burial on the eastern side of the lake. The site is also believed to be associated with a sacred narrative which discusses the specific formation of the lake during the Dreaming. Also, as outlined in section 2.2.7; Lake Ewlyamartup is within the boundary of the Wagyl Kaip and Southern Noongar native title claim areas. In December 2011, the DIA provided its consent to the Katanning LCDC, to improve water quality at Lake Ewlyamartup through the implementation of a restricted bypass, groyne, and gated flushing



channel. Further details of the Registered Sites and the Regulation 10 approval are contained in Appendix D.

Figure 23: Lake Ewlyamartup – Registered Aboriginal Site ID 4541 Source: On-line search of Aboriginal Heritage Inquiry System April 2012 As a result of the identification of Lake Ewlyamartup as a Registered Aboriginal Site, and in response to the conditions of the Katanning LCDC Regulation 10 approval (Refer Appendix D) any additions or modifications to the works as proposed by LEWG (2010) will require further inspection and consultation, as well as the submission of a new Regulation 10 application.



4.5. Existing Lake Modifications and Initiatives In relation to Lake Ewlyamartup, the JDA Feasibility Study is largely based on a review of existing engineering proposals that have been developed by the Lake Ewlyamartup Working Group (LEWG), a community group operating under auspices of Katanning LCDC. The LEWG proposals involve various options that continue to be progressively refined, but generally involve three components; Diversion - A restricted bypass north of bridge on Katanning –Nyabing Road to manage flow of

water from Ewlyamartup Creek into the lake. (The diversions are based on threshold flows - below the threshold level, water is diverted away from the lake, and above the threshold level water enters the lake).

Flushing overflow - A gated outlet channel to reduce residence times of salt and or nutrients within lake and flush water through to the Coblinine River.

In-lake mixing - An earthen groyne* at the lake entrance to encourage mixing of the water column.

*Note: In-lake works such as a groyne have not been considered in the Living Lakes feasibility study. The various LEWG options or combinations of options have been developed and analysed by a consultant hydrologist (Wheatbelt Hydrology 2011a,b,c) based on consideration of the following performance criteria; water quality improvement (to be less saline than seawater) waterlogging of fringing vegetation to be avoided depth and salinity of water to be suitable for wildlife species lake to be at a suitable depth for skiing (> 1.5 m) for a certain period each year.

In relation to the latter criterion, the Department of Transport (DoT) have indicated that a minimum depth of 2-3m is generally recommended for skiing, although private ski clubs will often operate with 1.2 to 1.3m depth. In its development of design options, Wheatbelt Hydrology (2011b) makes an important qualification that the analysis is indicative only and (due to relative paucity of data) the model should not be used to provide predictions of absolute values for any particular option. Furthermore according to the February 2011 Output Summary (Wheatbelt Hydrology 2011a) “no single, or combination of options so far achieves both the recreational and environmental objectives at the same time.” Given the existing momentum of the LEWG’s Lake Restoration project, and the need for a relatively consistent approach to the feasibility assessment for all three of the short-listed lakes, the Living Lakes consultant team objective for this lake has been two-fold. Firstly it is to provide an overview of the options developed to date by LEWG to assist effective due diligence consideration for potential investment by State Government into the project resulting from its alignment with Living Lakes objectives. Secondly, the consultant’s objective has been to provide additional baseline information (environmental data and modelling results) to assist LEWG in its own feasibility assessment process and progress through relevant approval processes, where such information is also required for the Living Lakes Feasibility study.



4.6. Living Lake Enhancements – Environmental Considerations Six enhancement options have been considered for Lake Ewlyamartup as part of the Living Lakes Feasibility Study. Although any recommended ‘hydrological solution’ to achieve the objectives of the Living Lakes initiative is likely to involve a combination of works in various areas, the individual enhancement options are outlined below with relevant locations and site features shown in Figure 24.

Figure 24: Enhancements Considered in Living Lakes Project – Lake Ewlyamartup Source: Jim Davies and Associates

4.6.1. EE1: Diversion The objective of this enhancement option is to enable interception and conveyance of the initial ‘break of season’ inflows from Ewlyamartup Creek (that are of lower volume but more saline) away from the Lake. At the time of field assessment a number of locations for a diversion structure on Ewlyamartup Creek had been put forward by LEWG ranging from just south of the Katanning Nyabing Road to approximately 1 km north of that road. The environmental considerations associated with this enhancement option are summarised as follows:

Options resulting in a significant increase in the volume of water directed into the lake need engineered so that there is no prolonged increase in the lake’s existing maximum level and hence no adverse effect on fringing vegetation.



The low-lying vegetation communities within possible locations proposed for a diversion structure are already degraded by salinity and likely to be well represented within the nearby Coblinine Nature Reserve. The slightly more elevated vegetation communities in these areas are of more variable condition.

At times when a diversion structure is directing Ewlyamartup Creek‘s higher salinity water away from the lake, this is likely to have little downstream effect on Coblinine Nature Reserve because its vegetation already reflects highly saline conditions.

At times when a diversion structure is directing Ewlyamartup Creek‘s lower salinity water into

the lake, this is likely to have little downstream effect on Coblinine Nature Reserve because the passage of water through the system is being assisted by a flushing channel and water is not being detained.

The northern location option for the diversion structure as put forward by LEWG passes through an area determined from site survey to contain quite acidic soil (raising the possibility of Acid Sulfate Soil issues) and an additional aboriginal heritage site with a relatively broad boundary (refer Figure 22).

DEC records show a Priority 3 (Poorly known species subject to threatening processes) species,

Melaleuca pritzelii, as occurring within the study area north of Katanning-Nyabing Road. A specific survey along any final diversion route would be required to determine its presence or absence and ensure extinction of local population did not occur.

Risk Assessment - Low – subject to the diversion channel avoiding un-degraded woodlands or shrublands, and that the resulting maximum water level within the lake not causing prolonged inundation (and possible death) of fringing native vegetation.

4.6.2. EE2: Flushing This enhancement option would provide a channel to more readily transfer water (and salt load) out of the lake and into the Coblinine River, in order to improve water quality. At the time of field assessment a number of locations for a flushing channel had been put forward by LEWG These ranged from a shortest possible linkage from the central eastern side of the lake, to a number of longer pathways starting in the north eastern part of the lake and proceeding parallel to either Katanning-Nyabing Road or to property boundaries. The environmental considerations associated with this option are summarised as follows:

LEWG’s suggested locations for a flushing channel have evolved with subsequent preferred options being better suited for earthworks and passing through flatter terrain near the Katanning-Nyabing Road rather than through the lunettes and undulating dunes on the central eastern side of the lake (refer Land unit mapping Figure 18).



Water flow needs to be contained within the channel to avoid inundation of an adjacent potential Priority Ecological Community (‘Eucalypt woodlands of the Western Australian Wheatbelt in good or better condition’). This is the area of Swamp Mallet, Wandoo and Yate woodlands as shown in Figure 21)

There is already a narrow degraded strip of vegetation adjacent and parallel to the southern

side of Katanning-Nyabing Road that contains a water main. This area might be used to co-locate the flushing channel to minimize additional clearing.

The adequacy of the landform gradient needs to consider in relation to the ability to convey water without significant risk of scouring and sedimentation, and its effect on the required width and clearing area.

Land unit mapping (Figure 18) shows the flushing outlet channel passes through three main land units F1, F3b and F4. The depth of clay within these units is approximately 50 cm, 10 to 30 cm and less than 10 cm respectively. At 1 m depth this outlet drain should therefore have a clay base at all times.

The potential impacts of an associated groyne structure (as proposed by LEWG 2010) have not

been considered here apart from noting its potential to provide a habitat area for birds including the locally important Hooded Plover, and its potential to exacerbate scouring along the lake shore following higher rainfall events.

Risk Assessment - Low – subject to water being contained in the flushing channel, and the resulting maximum water level within the lake not causing prolonged inundation (and possible death) of fringing native vegetation.

4.6.3. EE3: Dredging of Lake (increased depth) An enhancement option involving lake-bed dredging offers the potential to increase lake depth in some areas, with the option of depositing sediment off-site, or within the lake to create an island. The environmental considerations associated with this option are summarised as follows: In the absence of an additional source of water for the lake, dredging offers the potential for

greater depth and water longevity in some areas. If the excavated material was retained in lake it could create an island for wildlife refuge.

Dredging may increase habitat (deep water) for diving waterfowl but reduce the extent and

duration of shallow water for shorebirds if the existing shoreline is altered.

On the basis of limited sampling of lake bed and fringing soils, the potential for acid sulfate soil problems arising from exposure of dredged sediment to air is considered unlikely.



Any ‘wet-dredging’ activity would incur a risk of water quality impacts due to re-suspension of

sediment and nutrients and, although likely to be temporary, this could adversely affect waterbird fauna. Such risk would be largely avoided if works were able to be conducted within a dry lake bed situation (as in an earlier trial where lake entrance was bunded off).



Aboriginal cultural heritage values are assigned to all portions of the lake, and an enhancement option involving dredging is considered most likely to be an unacceptable impact in this regard.

Risk Assessment - High – due to the likely unacceptability of the effect of lake-bed disturbance on Aboriginal cultural heritage values, and uncertainty relating to potential impacts on benthic habitat and nutrient remobilisation.

4.6.4. EE4: Groundwater Replenishment This enhancement option involves providing an additional source of water to ‘top up’ the lake using groundwater bores sunk into a nearby palaeochannel. The environmental considerations associated with this option are summarised as follows: As with other water addition options, there would need to be a consideration of the effects of

any resulting change to the salinity of the lake, and to any increase in the lake’s maximum water level which could in turn adversely affect fringing vegetation and the risk of waterlogging within small portions of adjacent farmland.

Given existing salinity levels the addition of any fresher quality water available from a nearby palaeochannel would be beneficial.

Environmental considerations of this option also depend on current unknowns such as;

- potential availability of water from a palaeochannel, and - the location of a suitable abstraction site, and the means and route by which water would be

transferred to the lake. Risk Assessment - Low – assuming availability of groundwater of suitable quantity and quality, and that the resulting maximum water level within the lake does not result in prolonged inundation (and possible death) of fringing native vegetation.



4.6.5. EE5: LEWG Option G32 This is a specific design option put forward by LEWG’s hydrology consultant (Wheatbelt Hydrology 2011c) involving a combination of enhancements, namely a diversion channel (see Option EE1) and a flushing channel (see EE2). It differs from specific design option G41 only in terms of the design height of the outlet from the lake. The environmental considerations associated with this option are not specifically addressed here because potential environmental impacts are covered by the consideration of more generic options EE1 and EE2, and because feasibility will be primarily determined from evaluation of hydrological information. It is noted however that LEWG’s criteria for lake enhancement for this option includes no resulting increase in lake’s existing maximum level and hence no adverse effect on fringing vegetation. Risk Assessment - Low – because the risk assessed for the components addressed as EE1 and EE2 is not likely to be cumulative as both involve low risk in different areas. This is also subject to the resulting maximum water level within the lake not causing prolonged inundation (and possible death) of fringing native vegetation.

4.6.6. EE6: LEWG Option G41 This is a specific design option put forward by LEWG’s hydrology consultant (Wheatbelt Hydrology 2011c) involving a combination of enhancements, namely a diversion channel (see Option EE1) and a flushing channel (see EE2). It differs from specific design option G32 only in terms of the design height of the outlet from the lake. The environmental considerations associated with this option are not specifically addressed here because potential environmental impacts are covered by the consideration of more generic options EE1 and EE2, and because feasibility will be primarily determined from evaluation of hydrological information. It is noted however that LEWG’s criteria for lake enhancement for this option includes no resulting increase in lake’s existing maximum level and hence no adverse effect on fringing vegetation. Risk Assessment - Low – because the risk assessed for the components addressed as EE1 and EE2 is not likely to be cumulative as both involve low risk in different areas. This is also subject to the resulting maximum water level within the lake not causing prolonged inundation (and possible death) of fringing native vegetation.



5. LAKE YEALERING

5.1. Lake Values and Catchment Context Lake Yealering is a seasonal/intermittent saline lake forming a component of the 775 ha ‘Yealering Lakes System’ that is listed in A Directory of Important Wetlands in Australia (Environment Australia 2001). The Yealering Lakes System is not a Ramsar wetland (of international significance) but it is one of Western Australia’s 23 inland wetlands that have been categorised in the Directory as a wetland of national importance based on the following criteria; It is a wetland which plays an important ecological or hydrological role in the natural functioning

of a major wetland system/complex. It is a wetland which is important as the habitat for animal taxa at a vulnerable stage in their life

cycles, or provides a refuge when adverse conditions such as drought prevail (it is a major drought refuge area for waterfowl in the agricultural inland of southwestern Australia);

The wetland supports 1% or more of the national populations of any native plant or animal taxa (Red-kneed Dotterel (150, November 1984, White Water Lake, regional rank 1)

The wetland supports native plant or animal taxa or communities which are considered endangered or vulnerable at the national level.

The wetland is of outstanding historical or cultural significance. The primary waterbody forming Lake Yealering is approximately 160 ha in area and adjacent to the townsite. It is predominantly contained within C Class Reserve No 9610 which is vested with the Department of Planning and managed by the Shire of Wickepin for the purposes of ‘Recreation; Waterway’. Adjacent ‘swamps’ occupy approximately 240 ha and are predominantly contained within private land. Other lakes within the ‘Yealering Lakes System’ are encompassed within the Nonalling Nature Reserve located approximately 5 km to the north of Yealering townsite. They include Nonalling Lake, Brown Lake and White Water Lake. As shown in Figure 25 these lakes are not directly connected to Lake Yealering, and Figure 26 shows cadastral information for the lake and its surrounds. Lake Yealering is recognised as a regionally significant wetland within technical reports associated with the Avon River Basin Natural Resource Management Strategy (Avon Catchment Council, 2005). Lake Yealering has also been important locally and within the region for water-skiing and other water sports.



Figure 25: Lake Yealering System (Source: Environment Australia 2001)

Figure 26: Lake Yealering – Cadastre

‘Swamps’

Yealering Nature Reserve

Cuneenying Brook

Reserve 9610

Reserve 15672

‘Outlet’

Yealering –Pingelly Road



Figure 27 shows the catchment areas to Lake Yealering and the Upper Avon. They are referred to in this report as follows:

Lake Yealering Catchment Lake Yealering (and adjacent swamps); Boyning Gully west; Boyning Gully east; Boyning Gully south; Wogalin Gully north west, Wogalin Gully west, Wogalin Gully central and Wogalin Gully east - with a combined total catchment area of 63,700 ha (DoW B Degens pers comm).

Upper Avon Catchment Upper Avon Tributaries (Cuneenying Brook plus associated Yarling and Walellemining Brooks) – with a combined total catchment area of 34646 ha.

Figure 27: Lake Yealering Catchment Source: Background - Hydrographic catchments (DoW 2008) Landgate Shared Land Information Platform (SLIP) - online image accessed March 2012 The following description of the lake’s hydrology is adapted from the Department of Water’s 2006 Upper Avon River Recovery Plan (Section 20 – Yealering Lakes) (refer Figures 26 and 27). Inflow to the lake is from small tributaries (Wogalin and Boyning Gullies) that discharge first into winter-wet flats (‘swamp’) and then into the lake. The lake fills and then backfills the smaller lakes of the ‘swamp’. Away from the lake, to the south west, Yarling Brook, Cuneenying Brook, and Walellemining Brook combine to form the Upper Avon catchment area. Much of the water from this



catchment area of 34,646 ha naturally bypasses the lake. However the combined watercourse (referred to here as Cuneenying Brook), has at some time in the past been diverted* to flow into Lake Yealering through the ‘outlet’ on the north-western side when the stream flow level is higher than the lake level. Otherwise, stream flow from Cuneenying Brook is to the Avon River. * At the time of field inspection however, this sand-bagged diversion structure (within Reserve 15672) had ‘blown out’ and is no longer effective. The tributaries to Lake Yealering are considered to be the headwaters of the Avon River. The waterway is known as the Avon River downstream from their confluence and Lake Yealering, and this portion of the Avon catchment has sluggish drainage and contributes only periodic flows to the Avon River after high rainfall.


5.2.1. Overview The Department of Agriculture and Food’s broad-scale soil-landscape mapping over the south west agricultural area (http://spatial.agric.wa.gov.au/slip) provides an initial framework for consideration of the Lake Yealering environment. Soil landscape systems are defined as ‘areas with recurring patterns of landforms, soils and vegetation’ (Schoknect et al., 2004). The study area consists of three soil landscape systems: Coblinine : Broad valley floors – including Lake Yealering and adjacent, lunettes, sumplands or

‘swamps’ and broad alluvial plains. The geology here consists of alluvial deposits of sand, silt and clay (Cza), lacustrine deposits (Ql), and quartz sand deposits (Qd).

Kukerin: Gently undulating lateritic terrain - including the area on which Yealering townsite occurs. The geology here consists of laterite (Czl), colluvium and minor alluvium (Qc) over granitic rocks.

Yealering: Undulating rises to rolling low hills - generally west and south west of Yealering townsite. The geology here consists of granites & gniesses, largely blanketed by colluvium derived from underlying & adjacent bedrock

These systems are divided in the Yealering locality into a number of sub-systems and phases as shown in Figure 28 with associated Table 14 providing a description of relevant mapping units. Lake Yealering forms part of an area of connected sumplands located in a broad valley filled with alluvial (river-derived) and lacustrine (lake-derived) deposits. In such a landscape floodwaters are dispersed very slowly. The floodplain downstream from Lake Yealering is broad and generally poorly defined, with about 6% of its agricultural land currently salinity affected (DoW 2006).



Figure 28: Soil-landscapes - Lake Yealering Area Source: Background – Department of Agriculture and Food - Soil landscape systems (Verboom and Galloway 2004) accessed via Landgate Shared Land Information Platform (SLIP).



Table 14: Soil Landscape Map Units - Lake Yealering Area Soil landscape

Map Units

Description (dominant soils and landform)

Coblinine System: (Cb)

Broad alluvial plains and lacustrine plains. Mainly saline wet soils.

Cb2 Broad valley floors and alluvial plains. Saline wet soils, many grey shallow sandy duplex soils.

Cb3 Saline broad alluvial plains. Saline wet soils, minor sandy duplex and grey clays.

Cb4 Lakes, swamps, lunettes, swamps and dunes.

Cb4sl salt lakes phase

Cb4lf lake fringe phase

Kukerin System:

(Kk)

Gently undulating rises. Mainly sandy duplex and gravelly soils.

Kk1 Gravelly crests and slopes. Gravelly soils and minor sandy duplex soils.

Kk1s Sandy slopes and depressions within Kk1.

Kk3u Irregular gently undulating rises with granite. Sandy duplex soils.

Yealering System: (Yg)

Colluvial undulating rises. Sandy duplex soils and sandy gravels.

Yg2u Weakly lateritised terrain with sandy gravels and gravelly duplex soils.

Yg2s Depressions and lower slopes.

Yg3u Gently undulating upper to lower slopes; sandy duplex soils.

Yg3g Irregularly undulating terrain with rock outcrop.

Yg3d Gravelly ridges and irregular undulating terrain with loams and clays.

Yg6 Small perched lakes and swamps.

Source: Verboom, W.H, and Galloway, P.D. (2004). Corrigin Land Resources Survey. Land Resources Series No.20, Department of Agriculture, Western Australia.



5.2.2. Site Survey and Mapping Results Given the broad scale of soil landscape mapping shown in Figure 28, some ‘on-ground’ variation can be expected in soil and landform conditions. More detailed mapping of the component ‘land units’ (landform soil types) was therefore undertaken by Land Assessment Pty Ltd in early March 2012 as a basis for understanding the local environmental setting and the possible implications of lake enhancement options. Soil and landform conditions were examined through aerial photo interpretation and a subsequent 3 – 4 day field survey period during which soils were described at 56 geo-referenced ‘hand auger’ sites associated with, but not limited to, a lesser number of lake margin transects as shown in Figure 29. At each observation site soils were classified in accordance with the Department of Agriculture and Food’s WA Soil Group nomenclature (Schoknecht 2002) and the landforms described according to its Land Evaluation Standards (van Gool et al 2005). Representative soil samples were obtained from a number of sites for subsequent analysis of soil pH and salinity. Appendix A provides site summaries and associated data from the field survey work. The resulting land unit mapping for Lake Yealering is shown in Figure 30 and described in Table 15. Although site numbers were not sufficient to fully characterise soil conditions, the resulting mapping nevertheless provides significantly more detail than the existing published soil landscape mapping. In conjunction with the detailed vegetation mapping by Woodgis Environmental Assessment & Management, the land unit mapping provides an appropriate framework for consideration of areas around the lake where impacts may arise from any future changes to local hydrological conditions. Further detail of landform, soil and vegetation inter-relationships is provided within lake margin cross-section transect diagrams Y1 – Y9 contained in Appendix B. Transect diagrams were produced from field measurements involving a digital laser rangefinder, clinometer, staff gauge and measuring tape. Transect diagrams in Appendix B start (zero point), where possible, at water level at the time of field work. Actual water level at that time, in metres AHD, has been determined by correlation to reference points (such as staff gauges) that were subsequently surveyed by JBA surveyors. The approximate early March 2012 water level (zero point) for the Lake Yealering Transect diagrams Y1 – Y9 in Appendix B was 269.5 m AHD.



Figure 29: Location of Soil Sites and Transects - Lake Yealering Area



Figure 30: Land Unit Mapping - Lake Yealering Area Source: Land Assessment Pty Ltd Table 15: Soil Landscape Map Units - Lake Yealering Area

Land Unit


Description

Upland areas Wetlands and associated dunal terrain

U Crests and slopes outside valley floor W1 Wetland – main body of Lake Yealering

Broad valley floor and alluvial flats W2 Nearby sumplands and clay flats

F1 Deep sandy duplex soils (non-saline) W2a Winter-wet saline floodplain beyond W2

F2 Deep sandy duplex soils (saline) Wd Drainage pathways through wet terrain

F3 Shallow duplex soils (saline) L1 Lunette – higher areas > 2 m relief

Fd Drainage pathways – distinct L2 Lunette and sandplain – lower areas

Fd1 Drainage pathways - indistinct. Sf Samphire fringes of lunettes or low sandy rises.




5.3.1. Overview

Vegetation Systems and Associations

Within the Avon Wheatbelt Biogeographic Region, Lake Yealering is in the 346,580 ha Corrigin Vegetation System, as shown in Figure 25.

Figure 251: Extent of Corrigin Vegetation System Source: Shepherd, Beeston and Hopkins(2002) The Corrigin Vegetation System generally drains to the north into the Avon River through a well-organised but shallow drainage pattern (Beard, 1981). Kwongan (shrublands) occur on sandplains (with Banksia on deeper sands), woodlands on slopes and flats with patches of mallee and teatree thickets or teatree and samphire in valleys. The woodlands consist of Wandoo, York Gum, Salmon Gum and Red Morrell, with Flooded Gum along creeks and Brown Mallet on breakaways (Beard, 1981). The extents of the vegetation associations in the vicinity of the lake are summarised in Table 16.



Table 16: Extent of Vegetation Associations in the Vicinity of Lake Yealering System Association Total Extent Extent Uncleared % Uncleared

37 Shrublands; teatree thicket 39,385 ha 24,948 ha 63.3 %

125 Bare areas; salt lakes 3,489,858 ha 3,278,701 ha 94.0 %

949 Low woodland; banksia 218,194 ha 125,009 ha 57.3 %

953 Succulent steppe with thicket; teatree over samphire 9,928 ha 3,234 ha 32.6 % 1147 Shrublands; scrub-heath in the south-east Avon-Wheatbelt 42,855 ha 4,074 ha 9.5 %

Source: Government of Western Australia (2009) The vegetation system-associations occurring in the vicinity of the lake are shown in Figure 32.

Figure 32: Vegetation System-Associations in Vicinity of Lake Yealering Source: Shepherd, Beeston and Hopkins(2002)



The extents of the vegetation system-associations in the vicinity of the lake are summarised in Table 17. Table 17: Extents of System-Associations in the Vicinity of Lake Yealering

System Association Pre-European Extent

Current Extent % Remaining

CORRIGIN_37 2,425 ha 583 ha 24.0%

CORRIGIN_125 775 ha 85 ha 11.1%

CORRIGIN_949 715 ha 102 ha 14.4%

CORRIGIN_953 1,514 ha 406 ha 26.9%

CORRIGIN_1147 23,773 ha 2,691 ha 11.3% Source: Government of Western Australia (2009) Ecological Communities One TEC and one potential PEC were recorded by the DEC within 15 km of the centre of Lake Yealering (DEC database search reference number 40-1211EC). The TEC was perched wetlands of the Wheatbelt region with extensive stands of living Swamp Sheoak (Casuarina obesa) and Paperbark (Melaleuca strobophylla) across the lake floor (of Lake Toolibin). The buffer around this TEC extends to within 15 km of Lake Yealering, although the lakes themselves are approximately 30 km apart. The potential PEC was a mixed Proteaceae-Myrtaceae heath on a quartz ridge. Species Richness The portion of the wheatbelt containing Lake Yealering was modelled as supporting more than 50% of the species in one terrestrial biodiversity assemblage (T6) by McKenzie, Gibson, Keighery & Rolfe (2004) and three wetland biodiversity assemblages (W5, W6 and W13) by Halse, Lyons, Pinder & Sheil (2004), but Lake Yealering was not in or a potential candidate recovery catchment identified by Walshe, Halse, McKenzie & Gibson (2004) to optimise conservation of species (i.e. conserve a relatively large number of species through intensive management of a relatively small number of catchments). Flora DEC’s incomplete flora inventory for the immediate surrounds of Lake Yealering consists of six species (DEC, 2007)(Gibson, Keighery, Lyons, & Webb, 2004). The Threatened and Priority flora species recorded by the DEC within 15 km of the centre of Lake Yealering (DEC database search reference number 46-1211FL) are documented in Appendix E. Of these, the potential habitat onsite for the two Priority flora taxa that are associated with wetlands is discussed in Section 5.3.2.



Fauna Lake Yealering is not listed as an Important Bird Area (Birdlife Australia, 2012) but does provide a regionally significant habitat for waterfowl. Lake Yealering itself provides significant habitat for diving waterbirds in the form of extensive areas of deep (> 1 m deep) water of up to approximately 130 ha. Lake Yealering is at times of regional significance to birds, with the highest number waterfowl recorded being 13,493 birds counted in March 1992 (regional rank 14) (Environment Australia 2001). As listed in Appendix C, the diversity of fauna in the Lake Yealering’s locality is expected to consist of 8 frogs, 42 reptiles, 164 birds and 23 mammals (Bamford, 2012). The Threatened, Priority and Schedule fauna species recorded by the DEC within 15 km of the centre of Lake Yealering (DEC database search reference number Bennetts3963) are documented in Appendix C. Of these, the potential habitat onsite for the species associated with wetlands is discussed in Section 5.3.2.

5.3.2. Site Survey and Mapping Results Vegetation Field reconnaissance for vegetation and flora was undertaken 1-2 March, 2012. Nine major vegetation formations (defined in terms of the dominant species in the dominant strata/layer) were identified in the immediate vicinity of Lake Yealering. The vegetation formations in the immediate vicinity of Lake Yealering are shown in Figure 33 and the vegetation emanating out from the lake is shown in transects in Appendix B. The formations associated with wetlands were: herbland of samphire (much of which has replaced Melaleuca shrubland killed by salinisation

and inundation) shrubland of Melaleuca (which is in decline) woodland of Saltwater Sheoak (which some anecdotal information indicated has increased in

abundance around Lake Yealering). The herblands of samphires are much more extensive than mapped. The mapped boundaries largely coincided with the Tecticornia indica herbland on slightly higher ground and these were readily identified across the lakes with aerial photography. The boundaries of the lower Tecticornia pergranulata herbland appear to be dynamic and were not readily identified across the lakes with aerial photography (although boundaries may be mapped with higher resolution photography and/or photography from a different year to that supplied).



Figure 33: Vegetation Formations in Vicinity of Lake Yealering The vegetation (reflecting soils and landforms) was different between the north and east (dominated by York Gum), and west of Lake Yealering (dominated by Wandoo). An Acorn Banksia woodland (which was highly degraded) was only mapped on one lunette. This was on the eastern shore of Lake Yealering itself, which was the highest lunette visited. There were occasional plants located on other lunettes indicating similar sandy soils (e.g. Conospermum cinereum) but too few to infer they would once have been equivalent communities and Rock Sheoak over exotic grasses may have displaced Acorn Banksia woodlands on some dunes. There is local example of an intact Acorn Banksia woodland on the east side of the Wickepin-Corrigin Road, to the south west of Lake Yealering. The areas of vegetation in best condition were the woodlands and shrublands along the Wickepin-Corrigin Road, to the west of Lake Yealering. None of the ecological communities in vicinity appear to correspond with any of the 12 TECs endorsed by the WA Minister for the Environment in the Avon-Wheatbelt bioregion, (as at August 2010). The woodlands along the Wickepin-Corrigin Road, to the west of Lake Yealering may correspond to 1 of the 21 PECs listed by DEC Species and Communities Branch as occurring in the Wheatbelt Region



(as at 30 September 2011). Approximately 30 ha of woodland appears to fall under the broad definition of the PEC ‘Eucalypt woodlands of the Western Australian Wheatbelt’ in Good or better condition. The definition of this recently listed PEC is likely to be subject to refinement as data are collated on potential occurrences. DEC has been supplied details of sites to determine if areas should be considered occurrences of the PEC. The vegetation formations mapped are within the range expected from the regional mapping of vegetation associations and vegetation complexes. Species richness The species richness in the survey area appeared low due to the generally degraded (Very Poor condition) of the vegetation. Lunettes that were visited to the south of the main lake appeared to have been subjected to historic clearing. There was some anecdotal information to suggest that timber cutting may once occurred in the lake system for tannin production and charcoal production. The lunettes to the east of the lake appeared to have been degraded by inappropriate fire regimes. There was some anecdotal information to suggest that the lunette on the eastern shore of the main lake was once used as a firing range (but it is unclear whether there is a causal relationship). Flora

During the field survey 24 taxa abundant, dominant and/or readily identifiable plant taxa were recorded in the immediate vicinity of the lake, taking the total flora inventory to 30 taxa (as listed in Appendix E). None of the species recorded onsite are listed as: Threatened Species under the Commonwealth EPBC Act 1999 Threatened Flora (T) in the Wildlife Conservation (Rare Flora) Notice 2011 under the Wildlife

Conservation Act 1950 Priority Flora by DEC.

There is a low likelihood of Threatened or Priority flora occurring in the immediate vicinity of the Lake Yealering, as summarised in Table 18. Table 18: Likelihood of Significant Flora Occurring in Wetland Areas Around Lake Yealering

Taxa Status Lifeform Flowers Typical Habitat

Likelihood of Detection


Dampiera triloba 1

Erect perennial herb or shrub, to 0.5 m high.

Aug to Dec

Peaty sand, loamy sand Medium Low – species tends to

occur further west

Likelihood of Detection based on plant size, flowering and presence of features for ready field identification and life form. High= Expected To Be Detected and Confirmed If Present Medium = Expected To Be Detected (but not necessarily confirmed, i.e. doubt may remain regarding identification) if Present Low = Unlikely to be Detected at time of Survey even if Present Of note is the smooth-barked form of Eucalyptus sargentii, a species that usually has a prominent black butt. Whilst entirely smooth barked trees have previously been recorded between Kondinin,



Yealering and Corrigin, the extent/distribution and abundance of this form is poorly known (White, 2012). No definitive statements can therefore be made on the significance of the smooth-barked form of Eucalyptus sargentii. Relatively few individuals of this species were observed onsite, and these tend to be close to the high water mark of the lake system. The species is highly tolerant of salinity but may be susceptible to waterlogging. Several flora populations onsite are close to the inland extents of species which are common further to the southwest (e.g. Acorn Banksia Banksia prionotes). Fauna Of the 237 vertebrate animals that Bamford (2012) identified as likely to occur in the locality of Lake Yealering, 11 are both listed as Threatened or Priority Fauna, and dependent and/or associated with wetlands (Appendix C). An indication of the relative importance of Lake Yealering to these species is provided in Table C1 of Appendix E. This table shows for each species, the distribution and abundance of the Australian population, the highest numbers recorded at the lake and comments on whether the species breeds in the wheatbelt and whether populations are increasing, stable or declining. A fauna survey was not undertaken by Bamford Consulting Ecologists but on the basis of available literature, interpretation of vegetation (which was assessed in the field) as fauna habitat, and in consultation with Bamford Consulting Ecologists), the following comments to be made. Migratory shorebirds (Sandpiper species) have not been recorded in large numbers at Lake Yealering (Appendix E). However, this in part may reflect a focus on waterfowl counts, and the lake system collectively provide significant suitable habitat in the form of extensive areas of shallow (< 0.5 m deep) water and extensive areas of Samphire flats (herbland of Tecticornia species) which combined extend over more than 75 ha. Peregrine Falcons may use the abundance of waterbirds on Lake Yealering as a major food source. This raptor feeds almost entirely on other birds, although it also eats rabbits and other moderate sized mammals, bats and reptiles. Carnaby’s Black-Cockatoos may utilise the Sheoak trees around the periphery of the lakes as a non-preferred/minor food source. The main food source is seeds from hakeas, grevilleas, banksias and eucalyptus). Nest hollows were not searched for, but there are likely to be few if any along a lake fringe dominated by Casuarina obesa and Eucalyptus loxophleba (preferred trees are Eucalyptus wandoo which are upslope). The Rufous Fieldwren has not been recorded in at Lake Yealering (Appendix E). This species is more likely to be present in vicinity in samphire heaths and shrublands rather than open water. These vegetation formations are extensive to the west of Lake Yealering.



5.3.3. Factoring Influencing Approvals The requirement for, and/or level of a formal environmental impact assessments and approvals for Lake Yealering will likely involve consideration of: the Vegetation Associations and Vegetation Complexes are largely cleared. The EPA may apply a

presumption against any clearing (which includes draining and flooding, as well as direct clearing of land) in the vicinity of the lake as the portion remaining of most of the Vegetation Associations and Vegetation System-Associations are below the 30% threshold

the Lake Yealering System was listed in the Directory of Important Wetlands in Australia (Environment Australia 2001)

regionally significant habitat for waterfowl potentially regionally significant habitat at times for migratory shorebirds (Sandpiper species),

and the Eastern Great Egret, the Hooded Plover and Rufous Fieldwren The development of detailed engineering designs should include specific consideration of limiting impacts on: the eucalypt woodlands (which are a potential PEC) that may be susceptible to additional salinity

or inundation. Backswamps, if there was to be near total exclusion of water. There may be a positive impact

from some reduction in inundation and the main littoral tree species Casuarina obesa is tolerant of drought (Sayed, 2001) as well as waterlogging

the smooth-barked form of Eucalyptus sargentii, the significance of which is unknown due to limited regional records. Relatively few individuals were observed onsite and may be susceptible to waterlogging, should lake levels be raised.



5.4. Aboriginal Heritage As shown in Figure 34, a Registered Aboriginal Site (ID 4711) occurs on the western side of the lake and the cultural heritage values associated with this site are identified as ‘Artefacts / Scatter’. DIA advise that; this site (Lake Entrance) has previously been assessed as a place to which section 5 of the Aboriginal Heritage Act (AHA) applies with approximately 2000 artefacts being identified, including a good potential for there to be more in existence beneath the land surface.

The DIA Aboriginal Heritage Inquiry System also provides data for a number of non-registered sites that have potential to be affected by lake enhancement options. These are sites where information on cultural values has been lodged but considered insufficient for classification as a Registered Site.

The non-registered sites include six ‘artefacts / scatter’ sites within the lunette along the eastern side of the lake (ID 4682-4687 inclusive), and a ‘modified tree’ (ID 4680) and another ‘artefacts / scatter’ site (ID 4720), both in proximity to Cunyeening Brook within Reserve 15627. DIA advise that; It is possible that a review of J Sanderson’s 194 Thesis paper would enable further information to be gleaned which would add to the understanding of the archaeological values of the other six places.

In addition to Registered Aboriginal Site (ID 4711), the non-registered sites also need to be considered because, as stated with in Aboriginal Heritage Inquiry System printouts, “the AHA (Aboriginal Heritage Act) protects all Aboriginal sites in Western Australia whether or not they are registered”. Further details of all sites are contained in Appendix D. Also, as outlined in section 2.2.7; Lake Yealering is within the Gnaala Karla Booja native title claim area and DIA is unaware of any Aboriginal heritage surveys being undertaken over this area.

Figure 34: Lake Yealering – Registered Aboriginal Sites Source: On-line search of Aboriginal Heritage Inquiry System April 2012



5.5. Existing Lake Modifications and Initiatives In relation to Lake Yealering, the JDA Feasibility Study is largely based on a review of engineering options that were proposed during the development of a Recovery Plan for the Yealering Lakes section of the Avon River (Department of Water 2006) and subsequent communications between local landholders and Mr Darren Farmer, a surface water hydrologist (I Hill pers. comm. Feb 2010). The recovery planning process identified the community desire for high water levels in the lake for a longer period and proposed specific management actions including an assessment of; options for increased fresh flow from existing tributaries such as Boyning Gully diversion of water from Cuneenying Brook the hydro-period benefits and risks from additional groundwater discharge to the lake.

Mr Farmers input provided further suggestions including; a shallow waterway within the broad valley floor south of the lake to improve inflow, a shallow bund extending southwards from lunettes on the eastern side of the lake, completion of the existing bund on private property to the south of the lake (see dotted yellow

line within Figure 28) and the associated provision of an alternative outflow around the western side of the lake,

possible harvesting of inflow from Wickepin Road (western side of lake) and review of inflows and outflows at the north western side of the lake.



5.6. Living Lake Enhancements – Environmental Considerations Five enhancement options have been considered for Lake Yealering as part of the Living Lakes Feasibility Study. Although any recommended ‘hydrological solution’ to achieve the objectives of the Living Lakes initiative is likely to involve a combination of works in various areas, the individual enhancement options are outlined below with relevant locations and site features shown in Figure 35.

Figure 35: Enhancements Considered in Living Lakes Project – Lake Yealering Source: Jim Davies and Associates



5.6.1. EY1: Bund within Backswamps This enhancement option involves establishing bunds within the back swamp area to effectively direct a greater proportion of the water from the southern catchments away from the swamps and into the lake. The environmental considerations associated with this option are summarised as follows: The ‘Back Swamp’ area is less biologically productive than Lake Yealering (Murdoch University

staff – cited in DoW 2006) however there will be a need to retain some water flow to these areas.

Even with bunds redirecting some water away from parts of the swamp, there should still be

significant catchment area and runoff from adjacent lands (Figure 27).

To prevent ‘short-circuiting’ of water flows, the newly constructed bund will need to extend between the lunette immediate adjacent to the lake across to ‘high ground’. The land unit mapping (Figure 30) indicates this could be to the large area of unit L2 within private land to the south east of the lake.

For the lake margins to be effective in containing a higher water level a number of ‘gap areas’ in

the adjacent lunette need to filled (bunded) as recognised in the recovery plan (DoW 2006). Gaps occur adjacent to the south western side of the lake leading into backswamp area W2 (refer Figure 30), and between the northern end of the existing bund on private land (refer dotted yellow line within Figure 28) across to the lunette directly adjacent to the lake.

Consideration should be given to formation of a shallow waterway as part of constructing the

new bund in order to improve sluggish flows (as suggested in the advice to landholders by Mr D Farmer - I Hill pers. comm. Feb 2010).

While enhancing the main flow pathway into the lake, bunds have the potential to create

problems with backing up of water on the side away from the main flow pathway, and risking inundation of lower-lying areas of farmland.

Consideration should therefore also be given to the creation of an alternative outflow around

the western side of the lake to reduce the risk of inundation of farming land from any water ‘backed up’ on this side of the’ extended original bund’ (as suggested in the advice to landholders by Mr D Farmer - I Hill pers. comm. Feb 2010) and taking into account the registered Aboriginal Site (Refer Figure 34).

The existing (partial) bund within private land appears to be robust and without obvious signs of

slumping or soil dispersion, and with a good cover of stabilising samphire vegetation. Although



geotechnical testing of potential bund material is recommended, the performance of this existing bund suggests the in-situ soil material should be appropriate for any new bunds.

Any resulting increase to the water level above the lake’s existing maximum needs to consider

- effects on fringing vegetation around lake - some vegetation low on lunettes is relatively tolerant of salinity but not waterlogging - potential for flooding and decreased productivity on farmland flats - potential leakage through lunettes

Risk Assessment - Low to Moderate – due to uncertainty at this stage over extent and height of bunding, surface runoff inputs from various parts of the catchment, and potential impact on waterbirds. The assessed risk is also subject to the resulting maximum water level within the lake not causing prolonged inundation (and possible death) of fringing native vegetation.

5.6.2. EY2: Improvement of Outlet This enhancement option involves installing a gated structure in the outlet channel between the lake and the Corrigin to Wickepin Road in order to control water level and also potentially increase the amount of flushing and therefore improve lake water quality. The environmental considerations associated with this option are summarised as follows: The potential for sedimentation of the flow channel, near the outlet and within the lake, also

needs to be addressed as outlined in the recovery plan (DoW 2006) and would be practical to achieve at the time of construction.

As addressed in the bunding option EY1, consideration should be given to the creation of an

alternative outflow around the western side of the lake to reduce the risk of inundation of farming land (as suggested in the advice to landholders by Mr D Farmer - I Hill pers. comm. Feb 2010). This drainage would logically bypass the gated structure to flow into the outlet channel.

Risk Assessment - Low – because this enhancement would assist flushing and would not be of detriment to the adjacent vegetation. The assessed risk is also subject to the resulting maximum water level within the lake not causing prolonged inundation (and possible death) of fringing native vegetation.



5.6.3. EY3: Dredging of Lake (increased depth) An enhancement option involving lake-bed dredging offers the potential to increase lake depth in some areas, with the option of depositing sediment off-site, or within the lake to create an island. The environmental considerations associated with this option are summarised as follows;

In the absence of an additional source of water for the lake, dredging offers the potential for

greater depth and water longevity in some areas. If the excavated material was to be retained within the lake environment, an island could be

created for wildlife refuge.

Dredging may increase habitat (deep water) for diving waterfowl but reduce the extent and duration of shallow water for shorebirds if the existing shoreline is altered.

Dredging could help address concern expressed in the Recovery Plan (Department of Water 2006) about sedimentation near the outlet.

On the basis of limited sampling of lake bed and fringing soils, the potential for acid sulfate soil

problems arising from exposure of dredged sediment to air is considered unlikely.

Any ‘wet-dredging’ activity would incur a risk of water quality impacts due to re-suspension of sediment and nutrients and, although likely to be temporary, this could adversely affect waterbird fauna. Such risks would be largely avoided if works were able to be conducted within a dry lake bed situation.



Risk Assessment - High – due to the status of the lake as part of a wetland system of national importance, possible unacceptability of the effect of lake-bed disturbance on Aboriginal cultural heritage values, and uncertainty relating to potential impacts on benthic habitat and nutrient remobilisation.



5.6.4. EY4: Groundwater Replenishment This enhancement option involves providing an additional source of water to ‘top up’ the lake using groundwater bores sunk into a nearby palaeochannel. The environmental considerations associated with this option are summarised as follows:

As with other water addition options, there would need to be a consideration of the effects of any resulting change to the salinity of the lake and any increase in the lake’s maximum water level which could in turn adversely affect fringing vegetation and the risk of flooding adjacent farmland.

Given existing salinity levels the addition of any fresher quality water available from a nearby palaeochannel would be beneficial.

Environmental considerations of this option also depend on current unknowns such as; - potential availability of water from a palaeochannel, and - the location of a suitable abstraction site, and the means and route by which water would be

transferred to the lake.

Risk Assessment - Low –assuming availability of groundwater of suitable quantity and quality, and that the resulting maximum water level within the lake does not cause prolonged inundation (and possible death) of fringing native vegetation.

5.6.5. EY5: Gated System on Outlet Drain This enhancement option involves installation of gates on the portion of the outlet drain where it intercepts Cuneenying Brook. This would to enable water to be retained or released from the lake, and to direct water from this source into either the lake or the Upper Avon River. The environmental considerations associated with this option are summarised as follows:

This enhancement offers potential to control lake level and possible inflows from any diversion of Cuneenying Brook (tributary on western side).

A gate rather than a fixed walled structure is required to direct water into or out of the lake, and enable a flushing effect. Without flushing, the salinity of the lake would increase due to evaporative concentration, resulting in declining water quality.

Risk Assessment - Low to Moderate - depending on design and management of the structure in relation to lake water levels. The assessed risk is subject to the resulting maximum water level within the lake not causing prolonged inundation (and possible death) of fringing native vegetation.



6. CONCLUSIONS

Specific environmental considerations are identified in relation to the location, design and management of engineering structures associated with the lake enhancement options. The environmental significance of the lakes is highest in relation to their value as bird habitat. Lake Towerrinning provides habitat for a large number of waterfowl, and the Blue-billed Duck; and potentially regionally significant habitat at times for migratory shorebirds (Sandpiper species), and the Eastern Great Egret. Lake Ewlyamartup provides habitat for moderate numbers waterfowl and low numbers of Hooded Plover. Lake Ewlyamrtup also provides potentially regionally significant habitat at times for migratory shorebirds (Sandpiper species), and the Eastern Great Egret. Lake Yealering is listed in the Directory of Important Wetlands in Australia (Environment Australia 2001), provides habitat for large numbers of waterfowl; and potentially regionally significant habitat at times for migratory shorebirds (Sandpiper species), and the Eastern Great Egret, the Hooded Plover. Other values of significance that would require attention during an approvals process for all three lakes include the fringing remnant vegetation in areas where land clearing has been extensive, the location of Lake Towerrinning in a nature reserve, and cultural values (the entirety of both Lake Towerrinning and Lake Ewlyamartup are Aboriginal Sites and there are registered sites around Lake Yealering).

None of these values are ‘fatal flaws’ to lake enhancement in their own right. The enhancement options that provide additional water throughputs offer possible environmental benefits in reducing water salinity and maintaining or improving habitat. Of the lake enhancement options, only lake dredging is of higher risk due to the level of uncertainty relating to potential changes in water quality and interactions with underlying groundwater.

In hydrological terms the Living Lakes objective is to control the inflow and outflow of lake water so that its extent and depth are maintained for as long as possible at a desirable level. This level should be conducive to aesthetic and recreational use benefit whilst avoiding significant periods at a higher level where fringing vegetation is at risk, or significant periods at lower level where the lake is at lesser benefit in terms of its aesthetic and recreational use values.

At Lake Towerrinning, an existing outlet structure effectively controls the lake’s maximum water level, and similar structures are among the enhancements being considered for Lakes Ewlamartup and Yealering. Lake margin transect information obtained during the environmental consultant’s field investigations (Appendix B) indicate that the high water mark or level at which the existing vegetation communities grade from those that are more tolerant to prolonged inundation (at existing water quality) to those that are less tolerant, occurs at about 219 m AHD for Lake Towerrinning, 273 m AHD for Lake Ewlyamartup, and 271 m for Lake Yealering.



It is suggested that implementation of any engineering enhancements needs to be:

Assessed as being environmentally acceptable with manageable impacts to the existing environmental values

Accepted by the local community Able to be simply managed, and Accompanied by a program for monitoring effects.

For post-implementation monitoring it is suggested this should involve not just water levels, but also salinity and other aspects of water quality, and seek to quantify any effects on fringing vegetation, and on the magnitude and diversity of birdlife attracted to the lakes.

It is recommended that following any decision to implement enhancement options at one or more of the lakes, that RDL initiate a ‘Proponent Referral’ under Section 38 of Part IV of the EP Act to enable the EPA to make its determination on the need and level of any required environmental assessment and associated regulatory approvals. This process of referral would enable clarification of the extent and scope of any further studies that might be required to quantify possible impacts of the proposed lake enhancement measures on environmental values, above and beyond the scope the scope of work addressed here as part of the Feasibility Study.



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APPENDIX A SOIL DESCRIPTION SITE DATA

Separate document



APPENDIX B LAKE MARGINS – TRANSECT DIAGRAMS

Separate document



APPENDIX C FAUNA REPORT (Bamford Consulting Ecologists)

Separate document



APPENDIX D RESULTS OF ABORIGINAL HERITAGE ENQUIRIES

Separate document



APPENDIX E VEGETATION, FLORA AND FAUNA TABLES

Separate document

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