Mallee Catchment Management Authority Lake Wallawalla Vegetation and Aquatic Ecosystem Monitoring Program 2018

September 2018

Report title:

Lake Wallawalla Vegetation and Aquatic Ecosystem Monitoring Program 2018 Authors: Dr Peter Lind and Dr Timothy Wills GHD Pty Ltd 180 Lonsdale Street, Melbourne, Victoria, 3000 [email protected] Acknowledgements: This project was funded by The Living Murray. The Living Murray is a joint initiative funded by the New South Wales, Victorian, South Australian, Australian Capital Territory and Commonwealth Governments, coordinated by the Murray–Darling Basin Authority

The authors wish to thank Jennifer Munro and Andrew Greenfield of Mallee Catchment Management Authority for assisting GHD. Cover photo: Lake Wallawalla with Eucalyptus camaldulensis (River Red-gum) in foreground, taken on 18 April 2018.

© Mallee Catchment Management Authority With the exception of the Commonwealth Coat of Arms, the Murray-Darling Basin Authority logo and photographs, all material presented in this document is provided under a Creative Commons Attribution 4.0 International licence. (https://creativecommons.org/licenses/by/4.0/). For the avoidance of any doubt, this licence only applies to the material set out in this document.

The details of the licence are available on the Creative Commons website (accessible using the links provided) as is the full legal code for the CC BY 4.0 licence (https://creativecommons.org/licenses/by/4.0/legalcode ). Source: Licensed from the Mallee Catchment Management Authority under a Creative Commons Attribution 4.0 International Licence

MDBA’s preference is that this publication be attributed (and any material sourced from it) using the following: Publication title: Lind, P. and Wills, T. (2018). Lake Wallawalla Vegetation and Aquatic Ecosystem Monitoring Program 2018. The contents of this publication do not purport to represent the position of the Commonwealth of Australia or the MDBA in any way and are presented for the purpose of informing and stimulating discussion for improved management of Basin's natural resources. To the extent permitted by law, the copyright holders (including its employees and consultants) exclude all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this report (in part or in whole) and any information or material contained in it. Contact us

Inquiries regarding the licence and any use of the document are welcome at:

Jennifer Munro: [email protected]

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Executive summary

This study has established baseline aquatic ecosystem and vegetation conditions in Lake Wallawalla based on monitoring undertaken during April 2018. Ultimately, this study assessed the current conditions of the aquatic ecosystem and vegetation in the littoral zone and provides information on productivity, food sources and habitat available for fauna that utilise the lake. Major findings from this study are:  The results represent conditions at a water level of approximately 20.89 to 20.94 m AHD. This water level followed a continual decline that began when water level was approximately 21.67 m AHD during mid-December 2017.  In situ water quality of the lake was found to be satisfactory and comparable to conditions in the region. However, high dissolved oxygen (109.6 to 144.5%), pH (7.8 to 8.9) and turbidity (879 to 1,010 NTU) were likely due to a combination of high algal abundances and wind mixing.  Total nitrogen ranged from 3.2 to 6.9 mg/L and total phosphorus from 0.66 to 1.20 mg/L. These high nutrient concentrations are likely to be contributing to increased algal abundances and the risk of Cyanobacteria (Blue-green algal) blooms.  Phytoplankton, zooplankton and macroinvertebrate communities appear suitable to support populations of small-bodied native fish species. However, phytoplankton densities (as measured by chlorophyll-a) suggest that there was a high algal biomass during monitoring with concentrations ranging from 0.021 to 0.062 mg/L.  The current fish community was dominated by the exotic Mosquitofish (Gambusia holbrooki) although several native species were found to utilise the lake; Carp Gudgeon (Hypseleotris klunzingeri), Rainbowfish (Melanotaenia fluviatillis), Unspecked Hardyhead (Craterocephalus stercusmuscarum fulvus) and Flathead Gudgeon (Philypnodon grandiceps).  Filling of the lake has promoted substantial recovery of native aquatic flora and moisture- dependent terrestrial flora, including five species listed as rare or threatened in Victoria. Weed cover is very low.  Highest species richness and cover of native flora occurs in the ‘dry or recently receded’ zone; as water level recedes, moisture-dependent terrestrial vegetation is expected to colonise the exposed substrate.  Anecdotal evidence suggests that vegetation in the littoral zone is being actively utilised by waterbirds during foraging activities, with evidence (i.e. nests) of colonial breeding.  Based on the results of the April 2018 monitoring, it appears that Lake Wallawalla is a highly productive eutrophic or even hyper-eutrophic ecosystem characterised by high nutrients and turbidity and high primary productivity.  There is potential for the lake to act as a fish nursery for native fish species and to maintain or improve bird populations. However, the study represent baseline conditions only and additional monitoring during different seasons and at different water levels will contribute to the knowledge of the lake dynamics and health.  In additional to the management of water levels, catchment wide land and water management (e.g. nutrients controls and revegetation) would also be required for maximum benefits of the lake. This report is subject to, and must be read in conjunction with the limitations, assumptions and qualifications contained throughout the Report.

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Table of contents

Glossary ...... i 1. Introduction...... 1 1.1 Background to study ...... 1 1.2 Purpose of this report...... 1 1.3 Scope and limitations ...... 2 2. Study area ...... 3 2.1 Mallee region ...... 3 2.2 Lake Wallawalla ...... 3 3. Study locations ...... 7 3.1 Aquatic locations ...... 7 3.2 Vegetation sites ...... 7 4. Methods...... 9 4.1 Aquatic monitoring ...... 9 4.2 Vegetation monitoring ...... 10 5. Results ...... 14 5.1 Hydrology ...... 14 5.2 Aquatic monitoring ...... 15 5.3 Vegetation monitoring ...... 18 6. Discussion ...... 25 6.1 Aquatic monitoring ...... 25 6.2 Vegetation monitoring ...... 30 7. Conclusions ...... 32 8. Recommendations ...... 33 8.1 Overall ...... 33 8.2 Vegetation monitoring ...... 33 9. References ...... 34

Table index

Table 1 Wetland-dependent fish and invertebrate species in the Mallee CMA region (Mallee CMA, 2006b) ...... 5 Table 2 Aquatic monitoring locations (Datum - UTM GDA94) ...... 7 Table 3 Definitions of Plant Functional Groups used in the data analysis ...... 11 Table 4 In situ water quality results from Lake Wallawalla. Bold values exceed relevant ANZECC (2000) trigger value ...... 15 Table 5 Nutrient and chlorophyll-a concentrations from Lake Wallawalla. Bold values exceed relevant ANZECC (2000) trigger value ...... 16

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Table 6 Zooplankton abundance (per litre) from Lake Wallawalla ...... 16 Table 7 Macroinvertebrate communities from Lake Wallawalla. Values represent total abundances from the shallow and deep sites (number per two square metres) ...... 17 Table 8 Fish communities from Lake Wallawalla...... 18 Table 9 Water depth zone quadrat characteristics ...... 18 Table 10 Sapling and seedling data in relation to water depth zones ...... 21 Table 11 Species richness in relation to water depth zones ...... 21 Table 12 Native and introduced species cover in relation to water depth zones ...... 21 Table 13 Mean species cover in relation to water depth zones ...... 22 Table 14 Mean species frequency in relation to water depth zones...... 23

Figure index

Figure 1 Aquatic and vegetation monitoring sites at Lake Wallawalla ...... 8 Figure 2 Water level (m AHD) of Lake Wallawalla from November 2017 to May 2018. Figure supplied by the Mallee CMA...... 14 Figure 3 Discharge and electrical conductivity in the Lindsay River from 1 January 2017 to 7 March 2018. Data obtained from Gauging Station 414218...... 14

Appendices

Appendix A – Raw nutrient and chlorophyll-a results for each site at the eight locations Appendix B - Raw zooplankton results (per Litre) for each site at the eight locations

Appendix C - Raw macroinvertebrate results for each site at the eight locations

Appendix D – Vegetation quadrat raw data

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Glossary

CAMBA China–Australia Migratory Bird Agreement

CMA Catchment Management Authority

DELWP Department of Environment, Land, Water and Planning EC Electrical Conductivity EPBC Act Commonwealth Environment Protection and Biodiversity Conservation Act 1999

EVC Ecological Vegetation Class FFG Act Victorian Flora and Fauna Guarantee Act 1988

GHD GHD Pty Ltd

IWC Index of Wetland Condition JAMBA Japan–Australia Migratory Bird Agreement

PMST Protected Matters Search Tool

TLM The Living Murray VBA Victorian Biodiversity Atlas VROTS Species listed on DELWP’s Advisory List of Rare or Threatened Plants in Victoria – 2014

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1. Introduction

1.1 Background to study The Living Murray (TLM) is Australia’s largest long-term river restoration project and aims to achieve a healthy, working river by returning water to the environment including wetlands, floodplains and forests. Six icon sites are part of the restoration project including the Chowilla Floodplain that extends into New South Wales, South Australia and Victoria. The Lindsay, Mulcra and Wallpolla Islands comprise the Victorian component of the Chowilla Floodplain. Lake Wallawalla is the largest wetland within the Victorian component of the Chowilla Floodplain and provides important aquatic habitat for the region. In particular, the shallow littoral zone provides extensive mud flats for birds to forage for invertebrates and plants. Deeper water areas provide further habitat and feeding opportunities for dabbling and diving birds. Fish also utilise the lake and recruitment of fish communities is possible from the Lindsay River.

Under natural conditions, water levels would have been variable, with water periodically entering the lake from the Lindsay River during medium to large flows. However, following the Millennium drought (1997-2010), water has entered the lake more consistently due to a combination of environmental water allocations and natural flows, possible due to the construction of a regulator funded under ‘The Living Murray’ project, which has allowed the Mallee CMA to manage flows and ‘mimic’ natural wetting and drying regimes. While some monitoring of waterbirds and vegetation has previously occurred in Lake Wallawalla, particularly since 2010, there is a knowledge gap regarding the response dynamics of the ecosystem to water level changes. Given there is currently some discussion of using wetlands such as Lake Wallawalla as nursery areas and source populations for native fish, improved understanding of the macroinvertebrate and vegetation communities will aid in informing future planning and action relating to native fish restoration in the Lindsay River system and the River Murray between Locks 7 and 9. It would also aid in the management of bird communities associated with the lake.

This study aimed to provide information related to the response of macroinvertebrate and vegetation communities to the variable water levels in Lake Wallawalla. Specifically, the study assessed the current conditions of the aquatic ecosystem in the littoral zone to provide information on productivity, the food reserve and habitat available for birds and fish that currently or potentially utilise the lake.

1.2 Purpose of this report

The purpose of this study was to provide information on the productivity, food reserve and habitat in Lake Wallawalla. This report presents the results of aquatic ecosystem and vegetation monitoring undertaken during April 2018 to establish baseline conditions that can be compared to results of future monitoring at different water levels. The components of the monitoring that are presented and discussed are:

 Physical attributes of Lake Wallawalla (e.g. depth, hydrology, surface area);  Water quality (in situ and nutrients);

 Phytoplankton abundance (via chlorophyll-a concentrations);

 Zooplankton abundance;  Macroinvertebrate abundance and diversity;

 Fish abundance and diversity; and,

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 Vegetation communities.

Information gained through this study can aid the objective of the Mallee Regional Catchment Strategy (Mallee CMA, 2013) that aims to protect and enhance the environmental values of the Mallee’s wetlands and, in turn, the social, economic and environmental services that they provide to the community. Furthermore, the development of a wetland monitoring program to facilitate adaptive management of priority wetlands such as Lake Wallawalla has been identified as an action in the Mallee River Health Strategy (Mallee CMA, 2006a).

1.3 Scope and limitations

This report has been prepared by GHD for the Mallee Catchment Management Authority and may only be used and relied on by Mallee Catchment Management Authority for the purpose agreed between GHD and the Mallee Catchment Management Authority. GHD otherwise disclaims responsibility to any person other than the Mallee Catchment Management Authority arising in connection with this report. GHD also excludes implied warranties and conditions, to the extent legally permissible.

The services undertaken by GHD in connection with preparing this report were limited to those specifically detailed in the report and are subject to the scope limitations set out in the report. The opinions, conclusions and any recommendations in this report are based on conditions encountered and information reviewed at the date of preparation of the report. GHD has no responsibility or obligation to update this report to account for events or changes occurring subsequent to the date that the report was prepared. The opinions, conclusions and any recommendations in this report are based on assumptions made by GHD described in this report. GHD disclaims liability arising from any of the assumptions being incorrect.

GHD has prepared this report on the basis of information provided by the Mallee Catchment Management Authority and others who provided information to GHD (including Government authorities), which GHD has not independently verified or checked beyond the agreed scope of work. GHD does not accept liability in connection with such unverified information, including errors and omissions in the report which were caused by errors or omissions in that information. The opinions, conclusions and any recommendations in this report are based on information obtained from, and testing undertaken at or in connection with, specific sample points. Site conditions at other parts of the site may be different from the site conditions found at the specific monitoring locations. Site conditions (including the presence of hazardous substances and/or site contamination) may change after the date of this Report. GHD does not accept responsibility arising from, or in connection with, any change to the site conditions. GHD is also not responsible for updating this report if the site conditions change.

This ecological assessment covers vascular plant species, aquatic invertebrates and vertebrate fauna (fish). The flora assessment was conducted in autumn, which is generally considered to be a sub-optimal period for conducting flora monitoring in semi-arid areas, as annual species may not be more apparent and reproductive material may not be more available to facilitate easier identification. Consequently, not all flora species would have been identified at each site, due to their seasonal nature and/or lack of reproductive material. Additional species are likely to be recorded in late winter/early spring.

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2. Study area

2.1 Mallee region Lake Wallawalla is located 17 km northwest of Meringur North in the semi-arid Mallee region of Victoria (Figure 1). The Mallee region covers 39,939 km2 and the landscape is dominated by two broad landforms; the Riverine Plain that encompasses the floodplain of the River Murray and the undulating aeolian Mallee Dunefields (Mallee CMA, 2013). Native vegetation once covered nearly 40,000 km2, of which 52% is estimated to have been cleared for agriculture (Mallee CMA, 2013). Around 62% of the region is now dedicated to agriculture with important irrigation areas along the River Murray and extensive dryland cropping and grazing in other areas (Mallee CMA, 2013).

There are around 2,170 km of rivers and more than 900 wetlands across the region with 14 wetlands listed as Nationally Significant (Mallee CMA, 2013). Semi-permanent saline wetlands are the dominant type in the region and these have increased since European settlement due to altered hydrological regimes, native vegetation clearing, changes to land use, and the use of natural wetlands and other low lying areas for salinity management (Mallee CMA, 2013). The condition of waterways in the region are threatened by a range of pressures including altered flow regimes, salinity, invasive plants and animals, recreational activities, and adjacent land use practices (Mallee CMA, 2006a; Mallee CMA, 2013). Average summer temperature at Lake Wallawalla ranges from 17-32°C and winter from 4-15°C (DNRE, 1995). Annual rainfall is 250 mm although this is exceeded by evaporation, particularly over summer (DNRE, 1995). The climate is reflected in the hydrology of the Mallee Basin; despite being the largest in Victoria (28,027 km2) it contributes least to total annual streamflow across the State with a median annual runoff of ≤10 mm (DSE, 2005). Flooding tends to occur infrequently and is caused by heavy rainfall in localised areas (Mallee CMA, 2006a).

2.2 Lake Wallawalla

Lake Wallawalla is a nationally important wetland due to the following attributes (DNRE, 1995):

 It is a good example of a wetland type occurring within a biogeographic region in Australia; and,

 It 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 classified as an inland seasonal/intermittent fresh to brackish lake with a surface area of approximately 8.28 km2 and is 21 m above sea level (DNRE, 1995). The Index of Wetland Condition (IWC) classifies the lake as being in a moderate condition (Mallee CMA, 2014). Lake Wallawalla is an extension of the Lindsay Island wetlands system and under natural conditions, was periodically fed by the Lindsay River during floods (DNRE, 1995). On average the lake would fill once every four years and after filling could retain water for a full year (DNRE, 1995). However, river regulation in the Murray-Darling Basin combined with inlet structures changed the frequency, timing and duration of floods that contributed water to the lake (MDBC, 2006). This led to the lake flooding approximately two months later than usual, the flood level being almost 1 m lower, and floods being less frequent and of shorter duration (SKM, 2003; SKM, 2004). Coupled with the Millennium drought (1997-2010), the altered flow regime of the lake may have impacted vegetation, bird and fish communities (MDBC, 2006). However, following the Millennium drought (1997-2010), water has entered the lake more consistently due to a combination of environmental water allocations and natural flows, possible due to the

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construction of a regulator funded under ‘The Living Murray’ project, which has allowed the Mallee CMA to manage flows and ‘mimic’ natural wetting and drying regimes.

The lake supports a number of recreational, social and cultural values, and surrounding land use includes grazing and cropping (DNRE, 1995; Mallee CMA, 2014). The Lindsay River, which feeds into Lake Wallawalla, is categorised as being in a moderate condition (DSE, 2005). The upper Lindsay River is affected by inputs of saline groundwater (Mallee CMA, 2006a) and it has been reported that vegetation and water quality at Lake Wallawalla may be affected by saline inflow from the Lindsay River (DNRE, 1995).

2.2.1 Fish and bird communities

Fish

Nineteen species of native fish have been recorded in watercourses and wetlands in the Mallee region including the Murray Cod and the Murray Hardyhead, which are both listed under the Commonwealth Environment Protection and Biodiversity Conservation (EPBC) Act 1999 (Mallee CMA, 2013). A search of the Victorian Biodiversity Atlas (VBA) indicated that there has only been one aquatic species retrieved from Lake Wallawalla - Western Carp Gudgeon (Hypseleotris klunzingeri). However, the MDBC (2006) suggest that Flat-headed Gudgeon (Philypnodon grandiceps) and Murray Rainbowfish (Melanotaenia fluviatilis) are also present, and there is potential for Golden Perch (Macquaria ambigua) and Silver Perch (Bidyanus bidyanus) to utilise the lake. A search using the EPBC Act Protected Matters Search Tool (PMST) with a 1 km buffer indicated that the following species, or their habitat, may or are likely to occur in the region – the endangered Murray Hardyhead (Craterocephalus fluviatilis), the critically endangered Flathead Galaxias (Philypnodon grandiceps) and the vulnerable Murray Cod (Maccullochella peelii). In addition to these fish species, the vulnerable Growling Grass Frog (Litoria raniformis) or its habitat is also likely to inhabit the region. The Mallee CMA Wetland Management Strategy (Mallee CMA, 2006b) lists several wetland-dependent invertebrate and fish communities that are found in wetlands in the region (Table 1).

Birds

When flooded, Lake Wallawalla attracts a regionally significant number of waterbirds and 34 species have been recorded (MDBC, 2006). The Great Cormorant (Phalacrocorax carbo) has been observed breeding in the lake (MDBC, 2006) along with important populations of Black Swan (Cygnus atratus) and Australian Wood Duck (Chenonetta jubata)(DENR, 1995). Threatened birds that have been observed include the White-bellied Sea-eagle (Haliaeetus leucogaster) and Caspian Tern (Hydroprogne caspia), which are both listed under the China– Australia Migratory Bird Agreement (CAMBA) (MDBC, 2006). The Great Egret (Ardea modesta) and Greenshank (Tringa nebularia), both listed under both the Japan–Australia Migratory Bird Agreement (JAMBA) and CAMBA, also utilise the lake (MDBC, 2006). It has also been reported that five bird species found at Lake Wallawalla are listed under the Victorian Flora and Fauna Guarantee (FFG) Act 1988 and one species has been listed as vulnerable under the EPBC Act (MDBC, 2006).

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Table 1 Wetland-dependent fish and invertebrate species in the Mallee CMA region (Mallee CMA, 2006b)

Group Common Name Species name Agassiz's Chanda Perch Ambassis agassizii Silver Perch Bidyanus bidyanus Murray Hardyhead Craterocephalus fluviatilis Fly-specked Hardyhead Craterocephalus stercusmuscarum fulv Flat-headed Galaxias Galaxias rostratus Western Carp Gudgeon Hypseleotris klunzingeri Murray Cod Maccullochella peelii peelii Golden Perch Macquaria ambigua Fish Macquarie Perch Macquaria australasica Crimson-spotted Rainbowfish Melanotaenia fluviatilis Southern Purple-spotted Gudgeon Mogurnda adspersa Bony Bream Nematalosa erebi Flathead Gudgeon Philypnodon grandiceps Dwarf Flat-headed Gudgeon Philypnodon sp. nov. Australian Smelt Retropinna semoni Freshwater Catfish Tandanus tandanus Murray Freshwater Shrimp Caridina mccullochi Common Yabby Cherax destructor Hairy Burrowing Cray Engaeus sericatus Invertebrates Southern Freshwater Prawn Macrobrachium australi River Snail Notopala sublineata Common Freshwater Shrimp Paratya australiensis South-eastern River Mussel Velesunio ambiguus

Note: EX Extinct, CR Critically Endangered, EN Endangered, VU Vulnerable, RX Regionally Extinct, DD Data Deficient, L Listed

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2.2.2 Vegetation

Vegetation communities

During dry periods, the bed of Lake Wallawalla supports herbaceous communities including Lake Bed Herbland (EVC 107) and Alluvial Plains Semi-arid Grassland (EVC 806) (GHD 2014). The majority of the lake is fringed by Intermittent Swampy Woodland (EVC 813) dominated by Eucalyptus camaldulensis (River Red-gum) or E. largiflorens (Blackbox), together with Lignum Shrubland (EVC 808) in the north (GHD 2010). When inundated, wetlands such as Lake Wallawalla and the Mulcra Horseshoe Lagoon support aquatic flora species grown from both dormant seeds and propagules present in the lakebed, as well as those washed in by floodwaters (Ecological Associates 2007). As the lake dries, aquatic vegetation gives way to wetland herb communities (Ecological Associates 2007).

Flora

A search of the VBA on 4 May 2018 indicated that a total of 299 flora taxa (236 native, 63 introduced) have been recorded within a 5-km radius of Lake Wallawalla. Of these taxa, seven are listed as threatened under the FFG Act and a further 32 are listed as rare or threatened on the Advisory List of Rare or Threatened Plants in Victoria – 2014 (DEPI 2014). In addition, the PMST predicts the occurrence of three additional species listed under the EPBC Act. There is suitable wetland habitat at Lake Wallawalla for some of these 42 rare or threatened species recorded or predicted to occur in the local area.

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3. Study locations

3.1 Aquatic locations

A total of eight locations were monitored as part of the aquatic ecosystem monitoring (Figure 1). The eight locations were evenly spread around the perimeter of the lake and relate to the major compass points (i.e. north, northeast, east, etc.). At each location two depths were monitored; shallow littoral zone (<0.5 m) and a deeper zone (~1 m). GPS coordinates for each location and depth are included in Table 2.

Table 2 Aquatic monitoring locations (Datum - UTM GDA94)

Monitoring Site Code Eastings Northings North Shallow (NS) 517700 6218913 North Deep (ND) 517712 6218898 Northeast Shallow (NES) 518478 6218782 Northeast Deep (NED) 518420 6218729 East Shallow (ES) 518733 6217953 East Deep (ED) 518687 6217956 Southeast Shallow (SES) 518515 6217095 Southeast Deep (SED) 518455 6217116 South Shallow (SS) 517681 6216704 South Deep (SD) 517662 6216784 Southwest Shallow (SWS) 516737 6216776 Southwest Deep (SWD) 516805 6216875 West Shallow (WS) 516523 6217769 West Deep (WD) 516582 6217754 Northwest Shallow (NWS) 516823 6218385 Northwest Deep (NWD) 516860 6218364

3.2 Vegetation sites

A total of 72 vegetation quadrats were monitored across 24 locations around the outer margin of Lake Wallawalla (Figure 1). The 24 locations were spread around the perimeter of the lake, with eight locations approximating the major compass points (i.e. north, northeast, east, etc.) and coinciding with the aquatic site locations, while the remaining 16 locations were haphazardly located, with a requirement for each location to be at least 150 m from the nearest sampling location to maintain independence of sampling locations. At each location three 1 m2 plots were monitored at random points along a transect running perpendicular to the lake margin in each of three water depth zones shown in Figure 1:

 Green colour on map (plots marked as blue points) – inundated shallow littoral zone <0.25 m water depth;

 Steel blue colour on map (plots marked as green points) – inundated shallow littoral zone <0.05 m water depth to recently receded; and,

 Mauve colour on map (plots marked as red points) – water fully receded or dry.

Sample locations were not permanently marked.

GHD | Report for Mallee Catchment Management Authority - Lake Wallawalla Vegetation and Aquatic Survey, 3136086 | 7 Inlet Channel Outlet Channel

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Q33 Q32 Q31 ! ! "

Q28 Q30 Q29 " ! !

SE-D XW SE-S Q25 Q19 " XW Q26 " Q61 " ! Q20 Q64 " ! " Q62 ! Q21 Q27 ! Q1 ! Q65 ! Q63 " SW-D Q66 Q2 XW % S-D Q67 ! XWSW-S Q22 "XW " Q3 " Q68 ! " Q70 XW Q71 % ! S-S Q23 ! ! Q69 Q72 Q24 !

Legend Paper Size ISO A3 Mallee CMA Project No. 31-36086 Note: 0 0.1 0.2 0.3 0.4 Lake Wallawalla Aquatic invert & vegetation survey Revision No. - 3 (Flooded at time of 4 (Water receded or XW Aquatic Ecology Sites " ! Date May 2018 survey) dry at time of survey) No quadrats were sampled in Zone 1, which Kilometers Zones comprised water >20 cm deep at time of Aquatic and Vegetation % 3 (Water present but High water mark at Map Projection: Mercator Auxiliary Sphere 2 (Flooded at time of not inundated) time of Survey (16-19 survey Horizontal Datum: WGS 1984 o Monitoring Sites at " survey) April 2018) Grid: WGS 1984 Web Mercator Auxiliary Sphere ! 3 (Water receded or Lake Wallawalla FIGURE 1 dry at time of survey) H:\Data\31-36086-Wallawalla\GIS\Maps\Working\3136086_001_MonitoringSites_A3L.mxd Data source: Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community. Created by: tworth Print date: 24 May 2018 - 08:37

4. Methods

Monitoring of Lake Wallawalla occurred from 17-19 April 2018. Weather conditions during the monitoring were generally clear skies with no rain, a slight southwest breeze and air temperatures ranging from 22 to 30°C. The monitoring was designed to be repeatable and to allow statistical comparisons to be made following intervention monitoring at different water levels. As such, the results are generally presented here in a descriptive format to illustrate background conditions only.

4.1 Aquatic monitoring

4.1.1 Hydrology Ultimately, a specific aim of this study was to identify changes in ecological components of Lake Wallawalla (i.e. aquatic and vegetation) due to changes in water levels. To identify the water levels prior to and at the time of monitoring, data were obtained from the Mallee CMA. In addition to this, gauged discharge and electrical conductivity data were sourced from the Department of Environment, Land, Water and Planning (DELWP) for Gauging Station 414218 on the Lindsay River upstream of Lake Wallawalla.

4.1.2 Water quality At all locations in situ recordings of surface water temperature, dissolved oxygen (DO), pH and electrical conductivity (EC) were made with a calibrated YSI multiprobe. Turbidity was recorded with a Turbiquant Turbidity Meter and alkalinity using a HACH field titration kit. Water transparency was recorded using a Secchi disc. All recordings were taken in areas where depth was approximately 0.3 m. In addition to in situ recordings, water samples were collected from each depth at each location and transported to the NATA accredited ALS laboratory in Springvale, Victoria. The parameters

assessed were total nitrogen (TN), ammonia (NH3), total Kjeldahl nitrogen (TKN), nitrogen

oxides (NOx), nitrate (NO3), nitrite (NO2), total phosphorus (TP) and soluble reactive phosphorus (SRP).

4.1.3 Phytoplankton communities

The concentration of chlorophyll-a present in water is directly related to the amount of algae/phytoplankton. Therefore, an assessment of phytoplankton, and hence primary production, was made by assessing the concentration of chlorophyll-a. From each depth at each location, a one litre sample was collected and sent to the NATA accredited ALS laboratory.

4.1.4 Zooplankton communities At each site 100 litres of water was filtered through a 53 µm mesh to collect a zooplankton sample. Five replicates were collected from ach depth at each location to encompass spatial variability with replicates pooled to form a single composite sample. Samples were preserved in 70% ethanol. Individuals in the sample were identified to a broad taxonomic resolution to distinguish between the main forms (e.g. Copepoda, Rotifera, Cladocera and Ostracoda). Abundances per litre were calculated given that Rowland (1996) suggests the optimal density of zooplankton for juvenile native fish such as Golden Perch is 500-3,000 per litre.

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4.1.5 Macroinvertebrate communities

Macroinvertebrate communities were collected by sweep netting a 1 x 1 m quadrat using a hand-held sweep net. Five replicate samples were collected at each depth at each location to encompass spatial variability with replicates pooled to form a single composite sample. Samples were preserved in 70% ethanol. Individuals in the sample were identified in the GHD Aquatic Ecology laboratory to taxonomic resolutions consistent with EPA Victoria (2003).

4.1.6 Fish communities

The fish community at each location was assessed using a combination of fyke nets and baited box-traps. Note that the fyke nets and box-nets were only deployed in the deep area at each location as the shallow water depths at the shallow areas prevented the ability to capture fish. Furthermore, due to the large number of birds at the lake during the time of monitoring, grills were inserted into the open end of the fyke nets to prevent the accidental capture of birds (grills had a 50 x 50 mm aperture). Consequently, the fish monitoring was only aimed a assessing the communities of small-bodied fish with maximum body depths and widths <50 mm.

A double-winged fyke net with a 4 mm mesh was deployed for a maximum of 12 hours at each location. Two baited box-traps (2 mm mesh with entrance funnels of 40 mm) were also set at each location over the same time period. The twelve hour set times were repeated the following night at each location giving a total set time of approximately 24 hours. Fish monitoring was completed under GHD’s Department of Economic Development, Jobs, Transport and Resources (DEDJTR) Fisheries Act (1995) General Research Permit number RP1096, and the Department of Environment, Land, Water and Planning Permit (DELWP) Flora and Fauna Guarantee Act (1988) Research Permit number 10007730. All fish were identified, enumerated and returned at the point of capture. Exotic fish species (e.g. Mosquitofish and Carp) were euthanized in the field.

4.2 Vegetation monitoring

4.2.1 Quadrat sampling

The following data were recorded for each 1x1 m quadrat assessed:

 General information: plot identification code, date, assessor, GPS waypoint;  Water depth (cm);

 Water depth zone (see Section 3.2);  Water cover, bare ground cover, litter cover, coarse woody debris cover, cryptogam cover, bryophyte cover;

 General notes on bird activity, e.g. footprints, droppings, etc;

 Saplings <2 m high (number, height);

 Seedlings <0.25 m (number);

 Native cover, introduced cover; and,  Full vascular flora species list, including cover abundance estimate for each taxon using the following percentage cover scale:

– + Few individuals, no measurable cover (converted to 0.1% for data analysis purposes) – 1 Few to many individuals, c. 1% cover – 2 Few to many individuals, c. 2% cover

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– 5 c. 5% cover – Thereafter in 5% increments

4.2.2 Plant Functional Groups The ‘functional group’ approach has been widely used to assist in interpreting and predicting change in community function and dynamics (Brock and Casanova 1997; Kattel et al. 2009). Minor changes in species composition or inconsistencies in taxonomic resolution between years may affect between-year comparisons and the ability to detect ecologically significant changes in community structure. However, the use of functional groups helps detect changes in community structure based on plant responses to water regimes (Kattel et al. 2009).

For this study, each species was assigned a Plant Functional Group (PFG) based on common ecological, morphological and functional responses to inundation (PFGs are described in Table 3). PFGs were assigned to each species using an unpublished master list provided by Casanova et al. (2015)1.

Table 3 Definitions of Plant Functional Groups used in the data analysis

Abbreviation Plant Description Photo of example species (Casanova Functional 2015) Group Name

S Seed/spore Submerged born aquatic (Se, Sk or Sr) flora Adult plants do not survive prolonged exposure of the wetland substrate (drying) and lack perpetuating rootstocks. Seed or spores may persist in soil during dry times.

ARp Rhizomatous Amphibious fluctuation – aquatic flora responders floating Aerial parts of plants survive exposure of the wetland substrate (drying) for sustained periods of time. Plants survive drying by dying back to rootstocks.

ARf Semi-aquatic Amphibious fluctuation – flora responders plastic (includes strictly aquatic floaters) Can actively grow when substrate exposed but still moist, but may die back to rootstocks or seed during sustained dry periods.

1 Casanova et al. (2015). Unpublished master list of Plant Functional Groups. List was developed by experts in workshops.

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Abbreviation Plant Description Photo of example species (Casanova Functional 2015) Group Name

Atw Perennial Amphibious fluctuation tolerator, woody: Perennial woody species that require water to be present in the root zone but will germinate in shallow water or on a drying profile. Generally restricted to permanently saturated areas.

ATl Perennial Amphibious fluctuation – mudflat flora tolerates low growing Perennial – maintain same general growth form during brief periods of inundation, but may dieback to rootstocks if unable to develop emergent growth during sustained inundation.

ATl Annual mudflat Amphibious fluctuation – flora tolerates low growing Annual (or functionally so) – may tolerate very brief periods of shallow flooding during growth phase, but essentially short-lived plants which germinate following flood water recession and produce inundation-tolerant seed during the drying phase.

ATe Floodplain flora Amphibious fluctuation – tolerates emergent Rootstocks tolerate shallow inundation but plant intolerant of sustained total immersion. Recruitment and/or long-term maintenance.

Tda Moisture- Terrestrial damp dependent Rootstocks intolerant of more than superficial inundation, but occurring in areas of good soil moisture conditions, which may be influenced by proximity to river and water seepage through soil.

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Abbreviation Plant Description Photo of example species (Casanova Functional 2015) Group Name

Tdr Terrestrial dry Terrestrial dry Dry-land plants (i.e. flood intolerant and going through life cycles independently of flooding regime).

NA Not-vegetated Bare ground, litter, logs, water, etc

NA Not assigned Species for which there is insufficient information to assign them a PFG.

Source: Casanova et al. (2015). Note: images not necessarily from Lake Wallawalla.

4.2.3 Plant identification Taxa unable to be identified in the field were initially recorded to the nearest possible family or genus and a sample collected in accordance with the protocols of GHD’s Research permit / permit to take / keep protected flora under the Flora and Fauna Guarantee (FFG) Act 1988 and National Parks Act 1975 (No. 10008653). Taxa were subsequently identified to the finest possible level of taxonomic resolution using a dissecting microscope and the Flora of Victoria (https://vicflora.rbg.vic.gov.au/). A small number of infertile specimens that were difficult to identify were submitted to the National Herbarium of Victoria for identification. One taxon was unable to be identified and has been labelled as ‘underwater stoloniferous’ for the purpose of this report.

4.2.4 Nomenclature

Unless otherwise noted, common and scientific names for flora follow the VBA database (Version 3.0.7). Flora conservation significance was determined in accordance with the Victorian FFG Act 1988, the Advisory List of Rare or Threatened Plants in Victoria – 2014 (DEPI 2014) and the Commonwealth Environment Protection and Biodiversity Conservation (EPBC) Act 1999.

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5. Results

5.1 Hydrology The water level of Lake Wallawalla during the April 2018 monitoring ranged from approximately 20.89 to 20.94 m AHD (Figure 2). This followed a period of continual decline that began when water level was approximately 21.67 m AHD during mid-December 2017. Flow in the Lindsay River during the monitoring did not exceed 6.9 ML/day (Figure 3) in the month prior. During April 2018 it was observed that the lake was disconnected from the Lindsay River.

Figure 2 Water level (m AHD) of Lake Wallawalla from November 2017 to May 2018. Figure supplied by the Mallee CMA.

Figure 3 Discharge and electrical conductivity in the Lindsay River from 1 January 2017 to 7 March 2018. Data obtained from Gauging Station 414218.

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5.2 Aquatic monitoring

5.2.1 Water quality The in situ water quality results from each location are included in Table 4. Temperature was relatively constant throughout all locations and ranged from 17.2 to 22.0°C. Differences in temperature may be related to the time of day that recordings were made. Dissolved oxygen was high at all locations and ranged from 109.6 to 144.5% saturation. All but one of the locations exceeded the ANZECC (2000) trigger value for dissolved oxygen for the protection of aquatic ecosystems. ANZECC (2000) suggest that this should trigger an investigation to determine if the guidelines are appropriate based on the type of waterbody and the region. This is discussed further in Section 6.1.1. All locations also exceeded the trigger value for electrical conductivity that ranged from 1,190 to 1,270 µS/cm. However, the electrical conductivity trigger value is typical of values found in lakes and reservoirs in Tasmania and may be overly conservative for Lake Wallawalla. In fact, EC in Lake Wallawalla ranged from 1,190 to 1,270 µS/cm and was lower than the 2017 range in the Lindsay River (mean 1,676 ± standard error 134 µS/cm). The levels of pH also exceeded the ANZECC (2000) trigger value at the majority of locations and ranged from 7.8 to 8.9. Turbidity was noticeably high at all locations although ANZECC (2000) acknowledges that shallow lakes may have naturally higher turbidity due to wind-induced resuspension of sediments. The high turbidity levels are also reflected by the low Secchi depths that were found have a maximum value of 3 cm. Alkalinity was relatively high at all sites and ranged from 280 to 340 mg/L.

Table 4 In situ water quality results from Lake Wallawalla. Bold values exceed relevant ANZECC (2000) trigger value

ssolved

S/cm)

C)

° µ

Temperature ( Dissolved Oxygen (mg/L) Di Oxygen (%) Electrical Conductivity ( pH Turbidity (NTU) Alkalinity (mg/L) Secchi Depth (m) North 20.3 13.0 144.5 1,220 8.7 987 280 0.02 Northeast 20.6 12.8 143.1 1,190 8.8 925 300 0.02 East 21.0 12.1 136.3 1,210 8.8 952 280 0.02 Southeast 19.5 10.7 117.0 1,210 8.7 1,010 280 0.02 South 20.3 13.0 144.5 1,210 8.9 879 280 0.02 Southwest 17.2 10.5 109.6 1,200 7.8 980 280 0.02 West 22.0 9.7 111.5 1,270 8.4 988 320 0.03 Northwest 19.4 11.6 126.6 1,200 8.6 983 340 0.02 ANZECC - - 90 - 110 20 - 30 6.5 - 8.0 1 - 20 - - trigger value1

1. The ANZECC (2000) trigger values are those relevant to lakes and reservoirs in slightly disturbed ecosystems of south-east Australia.

Nutrient concentrations for all sites at the eight locations are included in Appendix A, while average concentrations for each location are included in Table 5. Overall, Lake Wallawalla had noticeably high nutrient levels with oxidised nitrogen (NOx), total nitrogen, total phosphorus and reactive phosphorus exceeding the ANZECC (2000) trigger values at all locations. The high NOx concentrations were predominately due to the nitrate component.

Of note is the high nitrate concentration at the north-east location compared to all other locations. It is possible that this is an outlier due to sample contamination of the shallow sample

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or laboratory error given that the shallow and deep sites at this location had concentrations of 1.67 and 0.03 mg/L respectively (see Appendix A). Despite this, the majority of nitrogen at all locations was in the form of organic nitrogen. A consequence of this is that total nitrogen concentration were up to 20 times the ANZECC (2000) trigger value. Reactive phosphorus and total phosphorus concentrations were on average 49 and 102 times the guidelines respectively.

Table 5 Nutrient and chlorophyll-a concentrations from Lake Wallawalla. Bold values exceed relevant ANZECC (2000) trigger value

N

a

-

-

(mg/L)

N (NOx

Ammoniaas (mg/L) Nitriteas N (mg/L) Nitrateas N (mg/L) Nitrite Nitrate + as mg/L) Total Kjeldahl Nitrogen N as (mg/L) Organic Nitrogen N as (mg/L) Total Nitrogen as N Total Phosphorus as P (mg/L) Reactive Phosphorus as P (mg/L) Chlorophyll (mg/L) North 0.03 0.01 0.03 0.03 3.2 3.2 3.2 0.66 0.25 0.044 Northeast 0.03 0.01 0.85 0.85 6.1 6.1 6.9 0.91 0.15 0.047 East 0.05 0.01 0.03 0.03 5.3 5.3 5.3 1.11 0.24 0.037 Southeast 0.03 0.01 0.04 0.04 5.9 5.9 6.0 1.08 0.31 0.044 South 0.04 0.01 0.04 0.04 6.1 6.1 6.2 1.07 0.27 0.052 Southwest 0.04 0.01 0.02 0.02 6.4 6.4 6.4 1.20 0.24 0.046 West 0.03 0.01 0.03 0.03 6.0 6.0 6.1 1.06 0.24 0.030 Northwest 0.05 0.01 0.06 0.06 6.0 5.9 6.0 1.08 0.25 0.042 ANZECC trigger - - - 0.01 - - 0.35 0.01 0.005 0.005 value1

1. The ANZECC (2000) trigger values are those relevant to lakes and reservoirs in slightly disturbed ecosystems of south-east Australia.

5.2.2 Phytoplankton communities Chlorophyll-a has been used as an indication of algal community abundance in Lake Wallawalla and concentrations for each location are included in Table 5. Chlorophyll-a ranged from 0.021 to 0.062 mg/L and all locations exceeded the ANZECC (2000) trigger value. The trigger value was exceeded by a magnitude of at least six and up to ten times.

5.2.3 Zooplankton communities Zooplankton densities for all sites at the eight locations are included in Appendix B while average densities are included in Table 6. Rotifera were the most common zooplankton taxa recorded from Lake Wallawalla followed by Copepoda and Ostracoda. Compared to the other taxon, Cladocera were relatively rare. There was variation in the distribution of zooplankton amongst the locations with total abundances ranging from 42 to 813 individuals per litre.

Table 6 Zooplankton abundance (per litre) from Lake Wallawalla

Location Copepoda Cladocera Ostracoda Rotifera Total Abundance North 101 6 10 422 539 Northeast 75 11 37 131 254 East 29 4 10 113 156 Southeast 13 3 1 88 105 South 50 20 12 167 250 Southwest 136 11 22 643 813 West 99 3 22 70 193 Northwest 17 1 14 9 42

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Total Abundance 522 60 127 1641

5.2.4 Macroinvertebrate communities Macroinvertebrate abundances for all sites at the eight locations are included in Appendix C while total abundances are included in Table 7. Seed Shrimp (Ostracoda) were by far the most common macroinvertebrate taxa recorded from Lake Wallawalla followed by Water Boatmen (Hemiptera: Corixidae), Non-biting Midges (Diptera: Tanypodinae) and Colonial Hydroids (Cordylophora: Clavidae) and Mayflies (Ephemeroptera: Caenidae). There was variation in the distribution of macroinvertebrates amongst the locations with total abundances ranging from 5,014 to 86,766 individuals. Diversity ranged from 13 to 18 with the lowest value at the south- west location.

Table 7 Macroinvertebrate communities from Lake Wallawalla. Values represent total abundances from the shallow and deep sites (number per two square metres)

Taxa

East West

East West

- -

- -

North North East South South South West North Total

Ceinidae 0 0 0 0 0 0 1 0 1 Hydridae 10 0 10 0 0 10 210 10 250 Dytiscidae 10 0 0 0 0 0 30 20 60 Dytiscidae (Larva) 0 10 20 0 0 0 50 20 100 Hydrophilidae 0 0 0 10 0 0 0 0 10 Clavidae 840 1700 100 0 0 10 220 120 2990 Atyidae 2 40 20 10 1 0 10 1 84 Parastacidae 1 10 2 1 10 2 2 20 48 Ceratopogonidae 160 140 200 120 230 110 240 500 1700 Chironominae 130 70 500 120 240 100 150 240 1550 Tanypodinae 10 440 500 80 610 1160 190 380 3370 Bryozoa 0 70 30 10 120 30 40 20 320 Caenidae 1130 250 180 180 10 10 260 900 2920 Ephemeroptera (immature) 0 0 1 0 0 0 0 0 1 Epiproctophora (immature) 0 0 0 10 0 0 0 0 10 Corixidae 371 850 900 680 830 700 450 440 5221 Notonectidae 110 130 260 170 70 10 30 140 920 Ancylidae 0 20 0 0 0 0 0 0 20 Oligochaeta 40 70 340 50 710 110 250 90 1660 Ostracoda 2180 2740 15460 17850 3820 9220 7110 6330 64710 Ecnomidae 0 0 30 10 10 0 20 20 90 Leptoceridae 20 40 70 260 80 80 30 150 730 Coenagrionidae 0 0 0 0 1 0 0 0 1 Total 5014 6580 18623 19561 6742 11552 9293 9401 Taxa Richness 14 15 17 15 14 13 18 17

5.2.5 Fish community Fish abundances at the eight locations are included in Table 8. A total of five small-bodied fish species were retrieved during the monitoring and this included one exotic and four native species. The exotic Mosquitofish (Gambusia holbrooki) were by far the most common small- bodied fish species recorded from Lake Wallawalla. Of the native species, Carp Gudgeon were

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found in greater abundances. The abundances ranged from 106 to 178 individuals at each location although Mosquitofish contributed to over 94% at all locations.

Table 8 Fish communities from Lake Wallawalla

East West

East West

- -

- -

North North East South South South West North Total

Mosquitofish Gambusia holbrooki 111 129 174 133 110 101 130 160 1048

Carp Hypseleotris klunzingeri 3 3 2 4 3 3 0 5 23 Gudgeon

Rainbowfish Melanotaenia fluviatillis 0 2 1 1 0 0 0 1 5

Unspecked Craterocephalus 0 2 1 1 2 2 0 0 8 Hardyhead stercusmuscarum fulvus Flathead Philypnodon grandiceps 0 1 0 0 0 0 0 0 1 Gudgeon Total 114 137 178 139 115 106 130 166 Species Richness 2 5 4 4 3 3 1 3

5.3 Vegetation monitoring

All vegetation quadrat data are provided in Appendix D.

5.3.1 Water Depth Zones

As outlined in Section 3.2, 24 1x1 m quadrats were sampled in each of three water depth zones. A summary of the characteristics of each depth zone is outlined in Table 9, with mean values and 95% confidence intervals provided for each variable.

Table 9 Water depth zone quadrat characteristics

Variable Inundated shallow Inundated shallow Dry or recently littoral zone <0.25 m littoral zone <0.05 receded depth m water depth or recently receded Figure 1 Blue points Green points Red points Mean water depth (cm) 13.5 ± 1.2 0.7 ± 0.6 0 Mean water cover (%) 100 21.9 ± 15.3 0 Mean bare ground cover (%) 0 63.5 ± 12.7 55.8 ± 7.0 Mean litter cover (%) 0 2.6 ± 2.0 5.3 ± 2.8 Mean CWD cover (%) 0 0 0.0 ± 0.1 Mean cryptogam cover (%) 0 0 0.5 ± 0.6 Mean bryophyte cover (%) 0 0 0

CWD: Coarse woody debris (>10 cm diameter)

Inundated shallow littoral zone <0.25 m depth

At the time of sampling this zone was characterised by a water depth of 13.5 ± 1.2 cm (Plate 1).

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Plate 1 Looking south-east from the inundated shallow littoral zone (<0.25 m depth) to the shore with large River Red-gums in the background

Inundated shallow littoral zone <0.05 m water depth or recently receded

This zone was characterised by recently receded substrate to water up to 5 cm deep (Plate 2). The majority (71%) of plots had no water cover; however, mean water cover across all plots was 21.9 ± 15.3%. Mean bare ground cover was 63.5 ± 12.7%, with litter cover minimal (2.6 ± 2.0%).

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Plate 2 Inundated shallow littoral zone (<0.05 m water depth or recently receded) The large majority (83%) of plots displayed considerable evidence of waterbird activity, either through presence of footprints or bird droppings.

Dry or recently receded This zone contained no water, with all sites either dry or recently receded at the time of sampling. Mean bare ground cover was 55.8 ± 7.0%, while litter cover was 5.3 ± 2.8%. Coarse woody debris and cryptogam cover were both below 1%. The large majority (71%) of plots displayed considerable evidence of waterbird activity, either through presence of footprints or bird droppings, with 29% of plots also showing signs of kangaroo activity (i.e. faecel pellets).

5.3.2 Eucalypt seedlings and saplings Saplings of Eucalyptus sp. (either E. camaldulensis or E. largiflorens) were only recorded at three of the 72 plots sampled, with all saplings recorded in the outer two zones where duration and frequency of inundation was lower (Table 10). Seedlings were only recorded at one of the 72 plots sampled, with 15 seedlings recorded in this plot, indicating a highly uneven seedling distribution (Table 10).

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Table 10 Sapling and seedling data in relation to water depth zones

Variable Inundated shallow Inundated shallow Dry or recently littoral zone <0.25 m littoral zone <0.05 receded depth m water depth or recently receded Mean no. saplings <2 m 0 0.0 ± 0.1 0.1 ± 0.1 Mean saplings <2 m (ht, cm) 0 165 152.5 Seedlings <0.25 m (no.) 0 0 0.6 ± 1.2

5.3.3 Species composition

A total of 18 taxa (15 native, three introduced) were sampled within the 72 1 m2 quadrats. All taxa, except Eucalyptus camaldulensis (River Red-gum), were herbaceous.

Species richness

Total species richness varied considerably, ranging from 0-8 in each quadrat. The deepest zone was species poor, with only four taxa present, while the dry/recently receded zone was the most species rich, with 14 taxa present (Table 11). Mean species richness followed a similar pattern: lowest in the deepest zone, highest in the dry/recently receded zone, and intermediate in the middle depth zone (Table 11).

Table 11 Species richness in relation to water depth zones

Variable Inundated shallow Inundated shallow Dry or recently littoral zone <0.25 m littoral zone <0.05 receded depth m water depth or recently receded Total species richness 4 8 14 Mean species richness 0.6 ± 0.2 2.0 ± 0.4 3.8 ± 0.8

Species distribution

Species distribution showed marked segregation according to depth zones, with nine species restricted to the dry/recently receded zone, two species restricted to the mid zone and one species restricted to the deeper inundated zone. Only two species occurred across all three zones.

Species cover Approximately 99% of vegetative cover across all quadrats comprised native species. Mean native cover followed a similar pattern to mean species richness, with cover lowest in the deepest zone, intermediate in the middle depth zone, and highest in the dry/recently receded upper zone (Table 12). Mean cover of introduced species was negligible across all zones.

Table 12 Native and introduced species cover in relation to water depth zones

Variable Inundated shallow Inundated shallow Dry or recently littoral zone <0.25 m littoral zone <0.05 receded depth m water depth or recently receded Mean native cover (%) 1.8 ± 0.9 14.9 ± 4.7 38.8 ± 6.7 Mean introduced cover (%) 0 0.3 ± 0.2 0.4 ± 0.2

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The dominant species in terms of cover was undoubtedly the graminoid, Sporobolus mitchellii (Rat-tail Couch), with Eleocharis acuta (Common Spike-rush) sub-dominant. All other species possessed a cover of 1% or less in each of the three zones (Table 13). The occurrence of rare and threatened flora is outlined in Section 5.3.4; however, it is important to note here that based on the sampling regime employed, all five rare or threatened species present at Lake Wallawalla are restricted to the dry/recently receded depth zone (Table 13). No rare or threatened species were recorded in the inundated shallow littoral zones.

Table 13 Mean species cover in relation to water depth zones

Species Status Inundated shallow Inundated shallow Dry or recently littoral zone <0.25 m littoral zone <0.05 receded depth m water depth or recently receded Ammannia multiflora v NP NP 1.0 ± 0.7 Austrobryonia micrantha r NP NP 0.0 ± 0.0 Bergia trimera v NP NP 0.2 ± 0.2 Centipeda nidiformis r NP NP 0.3 ± 0.2 Elacholoma prostrata r NP NP 0.0 ± 0.1 Eleocharis acuta 1.3 ± 0.9 3.0 ± 2.2 1.7 ± 2.8 Eucalyptus camaldulensis NP 0.0 ± 0.0 0.2 ± 0.4 Glossostigma sp. NP 0.0 ± 0.1 NP Haloragis aspera 0.1 ± 0.1 0.9 ± 0.9 0.8 ± 0.8 Heliotropium sp. * NP NP 0.0 ± 0.0 Limosella australis NP 0.2 ± 0.2 NP Medicago polymorpha * NP 0.3 ± 0.2 0.3 ± 0.2 Medicago sp. * NP NP 0.0 ± 0.0 Mimulus repens NP NP 0.1 ± 0.1 Potamogeton sp. 0.0 ± 0.1 NP NP Sporobolus mitchellii NP 11.4 ± 5.4 35.2 ± 7.2 Stemodia florulenta NP NP 0.1 ± 0.2 Underwater stoloniferous 0.4 ± 0.4 0.0 ± 0.1 NP v – vulnerable; r – rare; * - introduced; NP - not present Note – 0.0 indicates presence but a cover of zero when rounded to one decimal place.

Species frequency

The dominant species in terms of species frequency was undoubtedly the graminoid, Sporobolus mitchellii (Rat-tail Couch) (56% of quadrats), followed by Haloragis aspera (Rough Raspwort) (36%) and Eleocharis acuta (Common Spike-rush) (28%) (Table 14). The herbaceous weed, Medicago polymorpha (Burr Medic), was present at 17% of quadrats; however, its frequency and cover is likely to increase, as most individuals were recently germinated seedlings at the time of monitoring. The majority (10 out of 18) of species possessed a frequency of 4% or less across all 72 quadrats Table 14). Three out of the four most abundant native species (Sporobolus mitchellii (Rat-tail Couch), Haloragis aspera (Rough Raspwort), Ammannia multiflora (Jerry-jerry)) were categorised according to the Tda PFG, and as expected, mainly occurred in the two outer water depth zones where water had recently receded over the preceding months. Conversely, species of the inundated shallow littoral zone were characterised by more amphibious PFGs, e.g. ATe and ARp.

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Table 14 Mean species frequency in relation to water depth zones

Species Status PFG Inundated Inundated Dry or Total shallow shallow recently littoral littoral receded zone <0.25 zone <0.05 m depth m water depth or recently receded Ammannia multiflora v Tda 0 0 12 12 Austrobryonia micrantha r Tda 0 0 3 3 Bergia trimera v Tdr 0 0 8 8 Centipeda nidiformis r ATl 0 0 9 9 Elacholoma prostrata r ARp 0 0 1 1 Eleocharis acuta ATe 6 8 6 20 Eucalyptus camaldulensis Atw 0 1 2 3 Glossostigma sp. ATl 0 1 0 1 Haloragis aspera Tda 3 12 11 26 Heliotropium sp. * Tdr 0 0 1 1 Limosella australis ATl 0 3 0 3 Medicago polymorpha * Tdr 0 5 7 12 Medicago sp. * Tdr 0 0 2 2 Mimulus repens ATl 0 0 2 2 Potamogeton sp. ARf 1 0 0 1 Sporobolus mitchellii Tda 0 17 23 40 Stemodia florulenta Tda 0 0 3 3 Underwater stoloniferous ARp 5 1 0 6

v – vulnerable; r – rare; * - introduced; NP - not present

5.3.4 Rare or threatened species A total of five species listed as rare or vulnerable in Victoria under the Advisory List of Rare or Threatened Plants in Victoria – 2014 (DEPI 2014) were recorded during the monitoring. These species and their occurrence at Lake Wallawalla are described below, with information sourced from VicFlora2. Records of particular note include Centipeda nidiformis (Cotton Sneezeweed) and Elacholoma prostrata (Small Monkey-flower), both of which have not been previously recorded within 5 km of Lake Wallawalla.

Ammannia multiflora (Jerry-jerry) – Vulnerable (DEPI 2014)

Erect herb to 60 cm tall, rigidly-branched. Flowers throughout the year. Mostly confined in Victoria to the Murray River floodplain in the north-west on heavy soils, occasionally submerged. Monitoring indicated that this species had a strong preference for dry or recently receded sites.

Bergia trimera (Small Water-fire) – Vulnerable (DEPI 2014)

Prostrate or procumbent annual, forming loose mats to c. 20 cm diameter. Flowers mainly January to April (after summer floods). Rare in Victoria, confined to floodplains of the Murray River in the far northwest (Red Cliffs, Lake Wallawalla), and areas prone to inundation near Kerang. Rarely observed in the absence of recent floods. First collected in Victoria in 1982. Monitoring indicated that this species had a strong preference for dry or recently receded sites.

2 https://vicflora.rbg.vic.gov.au/

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Austrobryonia micrantha (Mallee Cucumber) – Rare (DEPI 2014)

Prostrate annual from a perennial rootstock. Flowers November to April. Occurs on drying or dried clay soils (e.g. lake-beds, ephemeral watercourses and lagoons) on the floodplain of the Murray River in the far north-west, with southerly occurrences at e.g. Lake Tyrrell, Wyperfeld National Park, but rare in Victoria. Monitoring indicated that this species had a preference for dry or recently receded sites.

Centipeda nidiformis (Cotton Sneezeweed) – Rare (DELWP 2014)

Decumbent to ascending cottony annual, spreading to c. 15 cm diameter and/or 15 cm high. Flowers mostly January to April. Scattered throughout the Murray Basin and around the Grampians along the margins of watercourses on clay or clay-loam soils. No previous records of this species within 5 km of Lake Wallawalla. Monitoring indicated that this species had a strong preference for dry or recently receded sites.

Elacholoma prostrata (Small Monkey-flower) – Rare (DELWP 2014)

Prostrate annual or perennial, forming broad mats, rooting at nodes. Flowers July to September. In Victoria, confined to north-western and north-central areas and rather uncommon. Mostly on heavy soils prone to seasonal inundation (gilgais, floodplains, etc.). No previous records of this species within 5 km of Lake Wallawalla. Monitoring indicated that this species had a preference for dry or recently receded sites.

Eleocharis acuta (Common Spike-rush) – not listed

There is a form of this species chiefly found in the far north-west of the State, on sandy or silty soils of lake and stream margins. These plants are smaller than in typical E. acuta, and have the bristles reduced. However, there are no obvious qualitative characters to separate this form from E. acuta. Further study is needed to establish the status of this form.

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6. Discussion

This study has established baseline aquatic ecosystem and vegetation conditions in Lake Wallawalla based on monitoring undertaken during April 2018. The results represent conditions in the lake at a water level of approximately 20.89 to 20.94 m AHD. This water level followed a continual decline that began when water level was approximately 21.67 m AHD during mid- December 2017. Ultimately, this study assessed the current conditions of the aquatic environment and vegetation in the littoral zone and provides information on productivity, food sources and habitat available for fauna that utilise the lake. The monitoring was designed to be repeatable and to allow statistical comparisons to be made following Intervention monitoring at different water levels. This would increase the knowledge regarding the response of macroinvertebrate and vegetation communities to variable water levels and aid in the management of the lake. This is important given that Kennard (2005) found that fish assemblages can demonstrate resilience to variable flow regimes provided that changes in flow and habitat resemble natural pre-disturbance conditions. Bird communities in Australian wetlands and floodplain lakes have also suffered due to alterations of natural flow regimes (Kingsford and Thomas, 2004). Outcomes from this study and future intervention monitoring will help to identify the capacity of Lake Wallawalla to act as a nursery area for source populations of native fish and in informing future planning and action relating to native fish restoration in the Lindsay River system and River Murray between Locks 7 and 9. It would also aid in the management of bird communities associated with the lake. Effective management of floodplain lakes and wetlands is often limited by a lack of hydrological and ecological knowledge (Davis and Froend, 1999). This study has established baseline conditions only, as changes in ecosystem components and hydrology cannot be made until additional monitoring has been completed. However, some aspects of Lake Wallawalla are discussed further below.

6.1 Aquatic monitoring

6.1.1 Water quality and phytoplankton communities Dissolved oxygen (DO), electrical conductivity (EC), pH and turbidity were high in Lake Wallawalla and exceeded the ANZECC (2000) trigger values for the protection of aquatic ecosystems. However, the EC trigger value is typical of values in lakes and reservoirs in Tasmania and may be overly conservative for Lake Wallawalla. In fact, EC in Lake Wallawalla ranged from 1,190 to 1,270 µS/cm and was lower than the 2017 range in the Lindsay River (mean 1,676 ± standard error 134 µS/cm). DO in water under ambient conditions is typically around 6 to 10 mg/L although super-saturation (>100%) may occur due to high algal abundance (DEHP, 2013). The high algal abundance in Lake Wallawalla (i.e. high chlorophyll-a), combined with wind mixing is likely to have contributed to observed DO levels. The shallow nature of the lake would also have contributed to the high turbidity due to wind disturbance, which is not uncommon for shallow lakes (ANZECC, 2000). Most freshwater has a pH in the range of 6.5 to 8.0 although in lakes with high algae densities pH may increase due to photosynthesis (ANZECC, 2000). Therefore, the in situ water quality conditions observed in Lake Wallawalla during April 2018 are not unexpected for a shallow lake in north-western Victoria. Nutrient concentrations were also high in Lake Wallawalla with oxides of nitrogen (NOx), total nitrogen (TN), reactive phosphorus (RP) and total phosphorus (TP) exceeding the ANZECC - (2000) trigger values for the protection of aquatic ecosystems. Nitrate (NO3 ) was the main contributor to NOx and can be delivered to waterways via organic matter, fertilizers, soil, manure and the breakdown of ammonia by bacteria. However, the major contributor to TN was

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+ organic nitrogen (ON). Typically, ON in surface waters is much higher than NH3 and NH4 (Wall, 2013) and this was found in this study. ON in lakes includes both dead and living organisms (Jorgensen, 2009) and the high concentrations observed may be due to a high abundance of phytoplankton as indicated by the chlorophyll-a concentrations. Phosphorus can be delivered to waterways from the catchment either in dissolved forms or a bound to sediments (Davis et al. 1998). While it is a natural element in rocks and other mineral deposits, delivery to waterways is often increased due to fertiliser use in the catchment (Davis et al. 1998). RP, or orthophosphate 3- (PO4 ), is the most available form of phosphorus for phytoplankton growth. Nitrogen + - - compounds, including NH3, NH4 , NO3 and nitrite (NO2 ), are also important sources of nutrients for phytoplankton. However, excessive concentrations of these nutrients can lead to algal blooms in waterways (e.g. Downing and McCauley, 1992). It appears that the delivery of nutrients to Lake Wallawalla are contributing to the high algal abundances and increasing the risk of bloom formations. However, large populations of water birds can also contribute to nutrient enrichment (Davis and Froend, 1999). The optimum ratio of nitrogen (N) to phosphorus (P) for uptake by algae varies greatly in the literature and for different algal species (see discussion by Wang and Wang, 2009). However, many limnologists use the ratio 7:1 (by mass) proposed by Redfield et. al. (1963). The Redfield ratio is not a universal optimum ratio, but an average of species-specific ratios. In this case, if the ratio exceeds 7 ± 1 then there is potentially an excess of N and the growth of algal or plant communities is likely to be limited by the availability of P. Alternatively, if the ratio is less than 7 ± 1 the water is considered N limited. Lake Wallawalla was found to have a N:P ratio of 5.6 suggesting that N is the limiting nutrient. This is often the case in lakes with a total phosphorus concentration greater than 0.03 mg/L (Downing and McCauley, 1992). When N is the limiting nutrient there is potential for Cyanobacteria (Blue-green algae) blooms to form due to their ability to fix nitrogen from the atmosphere (Bulgakov and Levich, 1999). Furthermore, Cyanobacteria are able to regulate their buoyancy and move into upper zones in the water column where there is more light (Lovett et al. 2007). This often occurs during periods of high turbidity, such as was found in Lake Wallawalla. Consequently, the conditions observed in Lake Wallawalla during April 2018 may be more favourable to Cyanobacteria compared to other algal taxon. This may be detrimental to aquatic fauna in the lake as Cyanobacteria produce toxins and subsequent death and decomposition of large blooms can reduce available dissolved oxygen (Lovett et al. 2007).

The high nutrient and chlorophyll-a concentrations, and low Secchi disc depths suggest that Lake Wallawalla is a eutrophic or even hyper-eutrophic ecosystem (see Carlson, 1977; Carlson and Simpson, 1996). This is also suggested by Downing and McCauley (1992) who found that the TN:TP ratio in eutrophic lakes ranged from 4 to 71, and in hyper-eutrophic lakes from 0.5 to 9. The eutrophication of lakes has the potential to cause the ecosystem to become more productive by nutrient enrichment thereby stimulating primary producers, causing algal blooms, water quality deterioration and potentially fish kills (Wang and Wang, 2009). In some ways the high algal abundances in Lake Wallawalla were not surprising as nutrient rich waters of floodplain wetlands support higher primary and secondary productivity than the associated river channels. This is particularly the case, after an initial lag time, following the addition of water that leads to a release of nutrients (Beesley et al. 2012). Nutrient enrichment is a common issues for floodplain wetlands and lakes in Australia, particularly in late summer and autumn as water levels decrease (Davis and Froend, 1999).

6.1.2 Zooplankton communities Zooplankton can provide a food source for many bird species (Loyn et. al., 2014) juvenile and larvae native fish including Murray Cod (King et. al. 2005), Silver Perch (Kuiter, 2013), Golden Perch (Lintermans, 2007) and other small-bodied fish species (e.g. Carp Gudgeon, Flat-headed

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Gudgeon, Dwarf Flat-headed Gudgeon, Unspecked Hardyhead and Murray-Darling Rainbowfish). Zooplankton have also been shown to be an important food source for fish associated with different functional food groups such as carnivores, omnivores and detritivores (Medeiros and Arthington, 2008). In lake ecosystems they are recognised as an important trophic link between primary production and higher order consumers (Medeiros and Arthington, 2008). Copepoda, Cladocera and Ostracoda, which were found throughout Lake Wallawalla, have also been shown to be important food sources for small-bodied fish in Australia (Medeiros and Arthington, 2008) and juvenile large-bodied fish (Ingram, 2001). This can be a benefit to higher order consumers, such as those in the Lindsay River system and the River Murray, as floodplain and wetland fish that feed on zooplankton can act as a food source after floods recede (Medeiros and Arthington, 2008). For fish species that do not directly use primary production as a food source (e.g. phytoplankton and aquatic plants), zooplankton can act as an important energy resource for small species and juveniles of large species that, in turn, provide energy to piscivorous fish and other higher order consumers (Medeiros and Arthington, 2008).

Rowland (1996) suggests the optimal density of zooplankton for juvenile native fish such as Golden Perch is 500-3000 per litre. Furthermore, zooplankton has been shown to be an important component of the diet of juvenile and small native fish with distinct shifts in diet composition across size classes (Medeiros and Arthington, 2008). Consequently, the zooplankton taxa and abundances found in this study suggest that Lake Wallawalla has some capacity to support native fish juveniles. However, Medeiros and Arthington (2008) also found that seasonal variation in zooplankton of floodplain habitats was influenced by changes in water availability. This emphasises the need for future monitoring of Lake Wallawalla at different water levels to fully understand ecosystem dynamics and the potential of the lake to act as a fish nursery.

6.1.3 Macroinvertebrate communities Macroinvertebrates have been shown to become an important food source for native fish species as they develop and grow (Ingram, 2001; Medeiros and Arthington, 2008). Seed Shrimp (Ostracoda) were by far the most common macroinvertebrate taxa recorded from Lake Wallawalla followed by Water Boatmen (Hemiptera: Corixidae), Non-biting Midges (Diptera: Tanypodinae) and Colonial Hydroids (Cordylophora: Clavidae) and Mayflies (Ephemeroptera: Caenidae). In floodplain habitats of the Macintyre River, eastern Australia, these macroinvertebrates, or similar taxa, were found to be a major contributor to the diet of native omnivorous fish (Medeiros and Arthington, 2008).

Kennard (2005) found that some small fish consume Water Fleas (Cladocera) and Non-biting Midges (Chironomidae), whereas larger individuals have a more diverse diet and mainly consume aquatic macroinvertebrates; mostly Non-biting Midges (Chironomidae), Water Boatmen (Corixidae), Backswimmers (Notonectidae), Mayflies (Ephemeroptera) and Caddsiflies (Trichoptera). Members of all these families were retrieved from Lake Wallawalla and therefore, the macroinvertebrate community found in this study, combined with the zooplankton community, should be able to provide food sources for a range of fish sizes. The flow regime is one of the most important drivers of ecosystem health, including macroinvertebrates and fish (Poff et al. 1997), vegetation and bird communities (Kingsford and Thomas, 2004). As previously mentioned, understanding the ecological dynamics of Lake Wallawalla through the monitoring of changes associated with variable water levels, is highly important in the management of the lake.

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6.1.4 Fish communities

Five species of fish were retrieved from Lake Wallawalla with the exotic Mosquitofish being by far the most abundant. This has been observed in many wetlands around Australia and may be contributing to the absence of other native fish (Davis and Froend, 1999). The high abundances of Mosquitofish may in part be due to them giving birth to large, fully formed juveniles, which are likely to be less vulnerable to predation and starvation and less dependent on the duration of flooding (Beesley et al. 2012).

The selective grazing of large Cladocera (e.g. Daphnia) by Mosquitofish can contribute to the development of algal blooms (Davis and Froend, 1999). European Carp (Cyprinus carpio) were not retrieved during the current study but anecdotal evidence of their presence was noted due to the presence of a large carcass above the high water mark. Mature Carp may not have been retrieved due to the presence of the exclusion grill in the fyke nets. Carp are known to contribute to water quality problems by uprooting aquatic vegetation and increasing turbidity (Beesley et al. 2012). It is possible that exotic fish are contributing to the water quality issues of Lake Wallawalla.

The native fish retrieved were Western Carp Gudgeon, Murray Rainbowfish, Unspecked Hardyhead (Craterocephalus stercusmuscarum fulvus) and Flat-headed Gudgeon. These species are known to occur in waterways in the region (Mallee CMA, 2006b; Beesley et al, 2012). These are similar results to those found by Beesley et al. (2012) in the semi-permanent wetlands of the mid-Murray River. Overall, given that several native fish species were retrieved, despite the adverse water quality conditions, it would appear that Lake Wallawalla has the capacity to provide habitat for small- bodied fish under current conditions. The small-bodied native species collected in this study (i.e. Carp Gudgeon, Unspecked Hardyhead, Flat-headed Gudgeon and Rainbowfish) have relatively short lifespans, are habitat generalists (Lintermans, 2007) and have been found to recruit successfully with limited flooding in wetlands and under low flow conditions in rivers (King et al. 2003; King, 2004). Furthermore, high food density, coupled with low competition and predation, is likely to increase the survival of larval fish (Beesley et al. 2012).

This relatively long period of inundation is likely beneficial to fish communities as small flooding events have been shown to provide little benefit except for maintaining refuge habitats (Beesley et al. 2012).

6.1.5 Suitability of Lake Wallawalla for fish and birds Wetlands can provide important habitats, and potential breeding and nursery areas for fish, especially juveniles and smaller-bodied species (Gawne et al. 2012). Beesley et al. (2012) discuss the factors that can influence the spatial and temporal dynamics of fish communities in floodplain wetlands that can include:

 The permanence of the aquatic habitat;

 The surrounding landscape that can affect colonisation and migration;

 Flood events that can change community structure through species loss and gain;  Habitat types and variability via species preferences (e.g. tolerances to water quality); and,

 Biotic interactions such as predation and competition. The wetting and drying cycles that characterise floodplain wetlands influence many of these factors either directly or indirectly (Beesley et al. 2012). These factors should be considered when assessing the suitability of Lake Wallawalla as a nursery area for native fish species. Some aspects of which are discussed further below.

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Native fish species such as Golden Perch have been reported to be able to withstand temperatures of 4-37°C (Merrick, 1976) and salinities up to 33,000 ppm or approximately 17,000 µS/cm (Llewellyn and MacDonald, 1980). The temperature and salinity levels of Lake Wallawalla during April 2018 were within this range. While dissolved oxygen was high at all locations, it is not known what concentrations were present during the night when respiration rates would exceed that of photosynthesis leading to a decrease in dissolved oxygen. However, there is some evidence that Golden Perch can survive when dissolved oxygen is 3 mg/L or even lower (Gilmore et. al., 2018). A minimum dissolved oxygen of 2 mg/L is also reported to be acceptable to fish (Gehrke, 1988). Low levels of pH are toxic to fish but overall, pH levels between 6.5 and 9.0 are considered satisfactory, on a long-term basis, for fish and other freshwater aquatic life (RBI, 2004). While algal respiration during the night has the capacity to decrease pH, the high alkalinity of Lake Wallawalla would buffer against major changes in pH (ANZECC, 2000). It has also been reported that juvenile native fish such as Murray Cod (Maccullochella peelii) are well adapted to turbid environments and are not inhibited in their ability to capture prey (Allen-Ankins et. al., 2012). High turbidity is common in Australian waterways and it was suggested native fish have adapted to such conditions (Allen-Ankins et. al., 2012). Therefore, based on the in situ conditions during this study, and the fact that native fish were retrieved, it appears that Lake Wallawalla has some capacity to support some native fish species. However, conditions are not ideal as there are high nutrients in the lake and potential for algal blooms. Native Australian fish such as Murray Cod have been shown to be unsettled in the absence of habitat and increase foraging behaviour when complex habitats such as woody debris is available (Allen-Ankins et. al., 2012). While no assessment of woody debris was made during the current study, it may need to be considered should it be used as a nursery. There was some woody debris observed in the lake during the study (Plate 3).

Plate 3 Littoral zone of Lake Wallawalla with evidence of woody debris The conditions during April 2018 are indicative of a water level of approximately 20.89 to 20.94 m AHD. As the wetland continues to dry, it is likely that water quality will deteriorate and the volume of habitat reduced, resulting in increased competition for limited resources, and higher risk of predation from large-bodied fish and birds (Junk et al. 1989). Fish communities in floodplain wetlands are largely shaped by the wetting/drying cycle including the magnitude, timing, duration and frequency of flooding (Beesley et al. 2012). It has been reported that younger fish (0+) tend to vary more than older fish (1+) and that longer periods of inundation

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benefitted younger fish such as Carp Gudgeon (Beesley et al. 2012). The body condition of Carp Gudgeon were also found to increase with duration of flooding (Beesley et al. 2012). A concern with using environmental water to create wetland habitat for fish is that the event will provide benefits to introduced species fish such as carp (Beesley et al. 2012).

Prior to the April 2018 study, Lake Wallawalla was gradually inundated over a number of months reaching a maximum depth mid to late December. Beesley et al. (2012) discuss the benefits to fish of a protracted filling during warmer months and suggest that this provides sufficient time for egg development and larval growth, the higher temperature promotes food production and increases metabolism, which in turn contribute to fish survival and recruitment.

6.2 Vegetation monitoring

The baseline vegetation monitoring at Lake Wallawalla revealed distinct patterns in relation to species composition, richness and frequency across a very narrow elevation gradient of approximately 0.30 m (i.e. approximately 0.15 m either side of the water level at the time of monitoring).

Recruitment of canopy species (i.e. eucalypts) was patchy and highly localised, as observed in other studies on the River Murray floodplain (e.g. George et al. 2005), with evidence of two different cohorts - seedlings <0.25 m (corresponding to 2016 flood) and saplings <2 m (probably corresponding to 2010-2012 flood). The patchy nature of eucalypt recruitment is most likely due to prevailing westerly winds pushing eucalypt seeds to aggregate in high densities near previous high water marks, particularly around the eastern shoreline. Total species richness, mean species richness and mean native cover all displayed similar trends – lowest in the inundated shallow littoral zone and highest in the dry or recently receded zone on the outer fringe of the lake bed. This is a commonly observed phenomenon in floodplain wetlands of the Murray-Darling Basin (e.g. Capon and Reid 2016), with species diversity maximised once the disturbance event (i.e. watering) has finished. While quadrats were not sampled in water deeper than 0.2 m, anecdotal evidence suggests that aquatic vegetation was concentrated in the littoral zone and exposed outer margins of the lake bed.

The distribution of species was also strongly affiliated with water depth zone, which is correlated to duration of inundation and time since inundation. Results from the 2010 (pre-flood) and 2013 (post-flood, dry lake bed) monitoring at Lake Wallawalla indicated that total and mean species richness was higher post-flood, while species composition also differed significantly after flooding (GHD 2014). As expected, in the current monitoring event, most species were specialists confined to a particular water depth zone (usually the dry or recently receded zone), while only a few were generalists that occurred across zones. This concurs with the PFG approach, whereby Tda (terrestrial moisture dependent species with rootstocks intolerant of more than superficial inundation) were dominant on the outer margins of the lake, which had been exposed over the preceding months, and amphibious species (e.g. Ate, ARp) were dominant in the shallow littoral zone. These results largely concurred with those of GHD (2014), which indicated a substantial increase in Tda and amphibious species following flooding. It is pertinent to note that the 2013 monitoring response is likely to be muted, given the post-flood monitoring was undertaken once the lake bed was fully dry, and some post-flood responders were likely to have already disappeared from the ‘above-ground’ component of the flora by the time monitoring was undertaken in December 2013. While overall species richness was relatively low at the time of monitoring, the richness and abundance of rare or threatened flora was impressive, with 28% of species observed being listed on the Advisory List of Rare or Threatened Plants in Victoria – 2014 (DEPI 2014). It is worth noting that none of the five rare or threatened species recorded in 2018 were recorded

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prior to flooding in the 2010 monitoring round at Lake Wallawalla (GHD 2014), while one vulnerable species, Bergia trimera (Small Water-fire) was recorded in December 2013 following natural flooding and environmental water allocations from 2010-2012 (GHD 2014). It is possible that some of the other rare or threatened species recorded in 2018 were present at Lake Wallawalla in 2013; however, they may have senesced prior to the December 2013 monitoring when the lake had dried out again. The relatively high proportion of rare or threatened species not previously recorded at Lake Wallawalla suggests that there is a degree of resilience in the system, whereby listed species can either persist through mega-droughts (e.g. the Millennium drought) or recolonise previously long-dry wetlands during floods. The variance in species composition emphasises the importance of sampling across multiple seasons at different stages of lake drawdown, to fully capture the vegetation response to watering. It also highlights the resilience of the flora, which for most species, endure dry periods through storage of seed or vegetative propagules in the lake bed sediments (Roberts et al. 2017). Introduced species were a very minor component of the flora at the time of monitoring. However, the data suggest that Medicago polymorpha (Burr Medic) may become locally common, as the lake draws down further. Anecdotal evidence indicated that in localised areas Burr Medic seed had been deposited in clumps around the margin of the lake following prevailing wave action as the water level decreased. Consequently, over coming months, annual weed cover on the recently exposed mudflats is likely to increase. The littoral zone is subject to heavy waterbird use, with large numbers of birds sighted during the monitoring, and evidence of bird activity (droppings, footprints) in almost all quadrats that were not inundated at the time of assessment. There was also substantial evidence to suggest that waterbirds were browsing on, or ripping up aquatic vegetation while foraging, namely Eleocharis acuta (Common Spike-sedge), with localised areas containing a relatively high density of recently detached and floating plant material. Consequently, in the shallow littoral zone, waterbird activity is likely to be a substantial and potentially significant influencer of vegetation cover. Evidence of colonial breeding was also observed in some large River Red- gums on the fringe of the lake, with over 15 nests observed in a single tree.

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7. Conclusions

This study has established baseline aquatic and vegetation conditions in Lake Wallawalla based on monitoring undertaken during April 2018. The following key points were determined:

 The results represent conditions in the lake at a water level of approximately 20.89 to 20.94 m AHD and this followed a continual decline from approximately 21.67 m AHD during mid- December 2017.  In situ water quality of the lake was found to be satisfactory and comparable to conditions in the region.

 High nutrient concentrations in the lake are likely to be contributing to increased algal abundances and the risk of Cyanobacteria (Blue-green algal) blooms.

 Phytoplankton, zooplankton and macroinvertebrate communities in the lake appear suitable to support populations of small-bodied native fish species.

 The current fish community is dominated by the exotic Mosquitofish although several other native species utilise the lake.

 Based on the results of the April 2018 monitoring, it appears that Lake Wallawalla is a highly productive eutrophic or even hyper-eutrophic ecosystem characterised by high nutrients and turbidity and high primary productivity.

 There is potential for the lake to act as a fish nursery for native fish species and to maintain or improve bird populations. However, the study represent baseline conditions only and additional monitoring during different seasons and at different water levels will contribute to the knowledge of the lake dynamics and health.

 In additional to the management of water levels, catchment wide land and water management (e.g. nutrients controls) would also be required for maximum benefits of the lake.

 Filling of the lake has promoted substantial recovery of aquatic flora and moisture- dependent terrestrial flora, including five species listed as rare or threatened in Victoria.

 Highest species richness and cover of native flora occurs in the ‘dry or recently receded’ zone; as water level recedes, moisture-dependent terrestrial vegetation is expected to colonise the exposed substrate.

 Anecdotal evidence suggests that vegetation in the littoral zone is being actively utilised by waterbirds during foraging activities, with evidence (i.e. nests) of colonial breeding.

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8. Recommendations

8.1 Overall  Additional aquatic and vegetation intervention monitoring at different water levels and during different seasons/years would contribute to the overall knowledge of ecosystem dynamics at Lake Wallawalla.

 Use of univariate (e.g. ANOVA) and multivariate statistics (e.g. ANOSIM) to compare results generated in this study to intervention monitoring at different water levels and seasons.

 Aquatic monitoring  The Draft Waters of Victoria SEPP has been released for consultation. These updated guidelines, including new guidelines relevant to wetlands, should be used to assess future water quality results.

 Nitrogen was determined to be the limiting nutrient and it is recommended that algal sample be collected and identified to see if Cyanobacteria are a potential issue.

 Dissolved oxygen loggers could be deployed to investigate if there are dramatic decreases in oxygen at night, especially warmer months.

 Specific study to identify sources of nutrients to Lake Wallawalla and/or Lindsay River. Or if this is known, then implementation of management strategies to attempt to decrease nutrient inputs.

8.2 Vegetation monitoring

 Avoid reducing replicate quadrat numbers (i.e. below 24) in each water depth zone, as 33% of the flora were present in only 1 or 2 of the 72 quadrats sampled.

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9. References

Allen-Ankins, S., Stoffels, R. J., Pridmore, P. A., & Vogel, M. T. (2012). The effects of turbidity, prey density and environmental complexity on the feeding of juvenile Murray cod Maccullochella peelii. Journal of Fish Biology, 80, 195–206. ANZECC. (2000). Australian and New Zealand Water Quality Guidelines for Fresh and Marine Water Quality. Beesley, L., King, A. J., Amtstaetter, F., Koehn, J. D., Gawne, B., Price, A., … Meredith, S. N. (2012). Does flooding affect spatiotemporal variation of fish assemblages in temperate floodplain wetlands? Freshwater Biology, 57, 2230–2246. Boevich, E. (1993). Lindsay Island. Draft. Background Paper and Interim Water Management Strategy. Brock, M.A., & Casanova, M.T. (1997) Plant life at the edge of wetlands: ecological responses to wetting and drying patterns. In: Klomp, N. & Lunt, I. (eds.) Frontiers in ecology: Building the links Elsevier Science). Bulgakov, N. G., & Levich, A. P. (1999). The nitrogen:phosphorus ratio as a factor regulating phytoplankton community structure. Archiv Für Hydrobiologie, 146(1), 3–22. Capon, S.J. & Reid, M.A. (2016). Vegetation resilience to mega-drought along a typical floodplain gradient of the southern Murray-Darling Basin, Australia. Journal of Vegetation Science, 27, 926- 937. Carlson, R. E. (1977). A trophic state index for lakes. Limnology and Oceanography, 22(2), 361–369. Carlson, R. E., & Simpson, J. (1996). A Coodinators Guide to Volunteer Lake Monitoring Methods. North American Lake Management Society. Casanova et al. (2015). Unpublished master list of Plant Functional Groups for species that occur within the Murray-Darling Basin. List was developed by experts in workshops and is work in progress, yet to be published. Provided by Michelle Casanova; Charophyte Services. Davis, J. A., & Froend, R. (1999). Loss and degradation of wetlands in southwestern Australia: Underlying causes, consequences and solutions. Wetlands Ecology and Management, 7, 13–23. Davis, R., Hamblin, A., O’Loughlin, E., Austin, N., Banens, R., Cornish, P., Weaver, D. (1998). Phosphorus in the landscape: diffuse sources to surface waters. DEHP. (2013). Monitoring and Sampling Manual 2009 - Environmental Protection (Water) Policy 2009. State of Queensland. DENR. (1995). Chowilla Regional Reserve and Chowilla Game Reserve Management Plan. DEPI. (2014). Advisory List of Rare or Threatened Plants in Victoria - 2014. Department of Environment and Primary Industries, East Melbourne, Victoria. DNRE. (1995). Directory of Important Wetlands. Downing, J. A., & McCauley, E. (1992). The nitrogen phosphorous relationship in lakes. Limnology and Oceanography, 37(5), 936–945. DSE. (2005). Index of Stream Condition: The Second Benchmark of Victorian River Condition. Victoria. Ecological Associates. (2007). Floodplain options investigation: Lindsay, Mulcra and Wallpolla Islands. Report prepared for Mallee CMA. EPA Victoria. (2003). Rapid Bioassessment Methodology for Rivers and Streams. Publication Number 604.1, October 2003. Southbank VIC, Australia. Gawne, B., Price, A., Koehn, J. D., King, A. J., Nielsen, D. L., Meredith, S., … Vilizzi, L. (2012). A Bayesian Belief Network Decision Support Tool for Watering Wetlands to Maximise Native Fish Outcomes. Wetlands, 32, 277–287. Gehrke, P. C. (1988). Response surface analysis of teleost cardio-respiratory responses to temperature and dissolved oxygen. Comparative Biochemistry and Physiology - Part A:

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Physiology, 89(4), 587–592. George, A.K., Walker, K.F. & Lewis, M.M. (2005). Population status of eucalypt trees on the River Murray floodplain, South Australia. River Research and Applications, 21, 271-282. GHD. (2014). Lake Wallawalla vegetation monitoring. Unpublished report for Mallee CMA. Gilmore, K. L., Doubleday, Z. A., & Gillanders, B. M. (2018). Testing hypoxia: physiological effects of long-term exposure in two freshwater fishes. Oecologia, 186(1), 37–47. Ingram, B. A. (2001). Rearing Juvenile Australian Native Percichthyid Fish in Fertislised Earthern Ponds. Deakin University. Jorgensen, N. O. G. (2009). Organic Nitrogen - Definition of Nitrogen Pools. In Encyclopedia of Inland Waters (pp. 832–851). Reference Module in Earth Systems and Environmental Sciences, Academic Press. Junk, W. J., Bayley, P. B., & Sparks, R. E. (1989). The flood-pulse concept in river-floodplain systems. Proceedings of the International Large River Symposium. Can. Spec. Publ. Fish. Aquat. Sci., (106). Kennard, M. J. (2005). A quantitative basis for the use of fish as indicators of river health in eastern Australia. King, A. J. (2004). Ontogenetic patterns of habitat use by fishes within the main channel of an Australian floodplain river. Journal of Fish Biology, 65, 1582–1603. King, A. J., Crook, D. A., Koster, W. M., Mahoney, J., & Tonkin, Z. (2005). RIPARIAN & STREAM ECOLOGY. Environmental Management and Restoration, 6(2), 136–138. King, A. J., Humphries, P., & Lake, P. S. (2003). Fish recruitment on floodplains: the roles of patterns of flooding and life history characteristics. Canadian Journal of Fisheries and Aquatic Sciences, 60, 773–786. Kingsford, R. T., & Thomas, R. F. (2004). Destruction of wetlands and waterbird populations by dams and irrigation on the Murrumbidgee River in Arid Australia. Environmental Management, 34(3), 383–396. Kuiter, R. H. (2013). Pictorial Guide to Victoria’s Freshwater Fishes. Seaford, VIC, Australia: Aquatic Photographics. Lintermans, M. (2007). Fishes of the Murray-Darling Basin - An introductory Guide. Canberra ACT, Australia: Murray-darling Basin Aithority. Llewellyn, C., & MacDonald, C. M. (1980). Family Percichthyidae. Australian Freshwater Basses and Cods. In R. M. McDowell (Ed.), Freshwater Fishes of South-eastern Australia. A. H. and A. W. Reed Pty Ltd, Sydney, pp 142-149. Lovett, S., Price, P., & Edgar, B. (eds). (2007). Salt, Nutrient, Sediment and Interactions: Findings from the National River Contaminants Program. Land and Water Australia, Canberra ACT. Loyn, R. H., Rodgers, D. I., Swindley, R. J., Stamation, K., Macak, P., & Menkhorst, P. (2014). Waterbird Monitoring at the Western Treatment Plant, 2000-12: The Effects of Climate and Sewage Treatment Processes on Waterbird Populations. Mallee CMA. (2006a). Mallee River Health Strategy. Mallee Catchment Management Authority, Irymple, Victoria, Australia. Mallee CMA. (2006b). Mallee Wetland Management Strategy 2006-11. Mallee Catchment Management Authority, Irymple, Victoria, Australia. Mallee CMA. (2013). Mallee Regional Catchment Strategy 2013-19. Mallee Catchment Management Authority, Irymple, Victoria, Australia. Mallee CMA. (2014). Mallee Waterway Strategy 2014-22. Irymple, Victoria. MDBA. (2012). Lindsay-Wallpolla Islands: Environmental Water Management Plan. Murray-Darling Basin Authority. Canberra ACT, Australia. MDBC. (2006). The Chowilla Floodplain (Including Lindsay-Wallpolla): Icon Site Environmental Management Plan 2006 – 2007. Environmental Management. Canberra ACT, Australia.

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Medeiros, E. S. F., & Arthington, A. H. (2008). The importance of zooplankton in the diets of three native fish species in floodplain waterholes of a dryland river, the Macintyre River, Australia. Hydrobiologia, 614, 19–31. Merrick, J. R. (1976). The waters and fish of the Lake Eyre basin. Part II. The Royal Society of New South Wales, Newsletter (14). Poff, N. L., Allan, J. D., Bain, M. B., Karr, J. R., Prestegaard, K. L., Richter, B. D., … Stromberg, J. C. (1997). The Natural Flow Regime: A paradigm for river conservation and restoration. BioScience, 47(11), 769–784. RBI. (2004). pH Requirements of Freshwater Aquatic Life - Technical memorandum. Redfield, A. C., Ketchum, B. H., & Richards, F. A. (1963). The influence of organisms on the composition of sea-water. In M. N. Hill (Ed.), The sea. Ideas and observations on progress in the study of the seas, vol. 2. The composition of sea-water comparative and descriptive oceanography (pp. 26–77). New York, London: Interscience Publishers, a division of John Wiley and Sons. Roberts, J., Casanova, M.T., Morris, K. & Papas, P. (2017). Vegetation recovery in inland wetlands: an Australian perspective. Arthur Rylah Institute for Environmental Research. Technical Report Series No. 270. Department of Environment, Land, Water and Planning, Victoria. Rowland, S. J. (1996). Development of techniques for the large-scale rearing of the larvae of the Australian freshwater fish golden perch, Macquaria ambigua (Richardson, 1845). Marine and Freshwater Research, 47(2), 233–242. SKM. (2003). Improving the flow regime of Lake Wallawalla. SKM. (2004). Concept regulator designs for Horseshoe Lagoon, Webster’s Lagoon and Lake Wallawalla. Wall, D. (2013). Nitrogen in Waters: Forms and Concerns. Wang, H., & Wang, H. (2009). Mitigation of lake eutrophication: Loosen nitrogen control and focus on phosphorus abatement. Progress in Natural Science, 19(10), 1445–1451.

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Appendices

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Appendix A – Raw nutrient and chlorophyll-a results for each site at the eight locations

)

L

(mg/

a

-

mg/L)

-

mg/L)

Ammonia as N (mg/L) Nitrite as N (mg/L) Nitrate as N (mg/L) Nitrite + Nitrate as N (NOx Total Kjeldahl Nitrogen as N (mg/L) Total Nitrogen as N (mg/L) Total Phosphorus as ( P Reactive Phosphorus (mg/L)as P Chlorophyll North - Shallow 0.02 <0.01 0.02 0.02 0.5 0.5 0.24 0.23 0.041 North - Deep 0.03 <0.01 0.03 0.03 5.8 5.8 1.08 0.26 0.047 Northeast - Shallow 0.03 <0.01 1.67 1.67 6.6 8.3 0.92 0.11 0.049 Northeast - Deep 0.02 <0.01 0.03 0.03 5.5 5.5 0.90 0.18 0.045 East - Shallow 0.06 <0.01 0.02 0.02 5.4 5.4 1.09 0.21 0.029 East - Deep 0.03 <0.01 0.04 0.04 5.2 5.2 1.13 0.26 0.044 Southeast - Shallow 0.03 <0.01 0.06 0.06 5.5 5.6 1.04 0.30 0.052 Southeast - Deep 0.03 <0.01 0.02 0.02 6.3 6.3 1.11 0.32 0.036 South - Shallow 0.05 <0.01 0.06 0.06 6.5 6.6 1.11 0.24 0.055 South - Deep 0.03 <0.01 0.02 0.02 5.7 5.7 1.03 0.29 0.048 Southwest - Shallow 0.03 <0.01 0.03 0.03 6.6 6.6 1.22 0.18 0.053 Southwest - Deep 0.04 <0.01 0.01 0.01 6.1 6.1 1.18 0.29 0.038 West - Shallow 0.02 <0.01 0.05 0.05 5.9 6.0 0.88 0.23 0.025 West - Deep 0.03 <0.01 <0.01 <0.01 6.1 6.1 1.24 0.25 0.034 Northwest - Shallow 0.04 <0.01 0.09 0.09 4.8 4.9 0.90 0.21 0.021 Northwest - Deep 0.06 <0.01 0.03 0.03 7.1 7.1 1.26 0.28 0.062

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Appendix B - Raw zooplankton results (per Litre) for each site at the eight locations

Copepoda Cladocera Ostracoda Rotifera Total Abundance (per Litre) North-Shallow 81 1 4 19 106 North-Deep 121 12 15 824 972 Northeast-Shallow 76 13 61 93 243 Northeast-Deep 75 10 12 168 264 East-Shallow 34 7 18 177 235 East-Deep 25 2 2 48 77 Southeast-Shallow 12 4 2 120 137 Southeast-Deep 15 1 1 56 73 South-Shallow 62 36 22 242 363 South-Deep 38 4 2 92 136 Southwest-Shallow 161 12 9 1111 1293 Southwest-Deep 111 9 36 175 332 West-Shallow 72 1 31 62 166 West-Deep 126 5 12 78 220 Northwest-Shallow 9 1 16 9 35 Northwest-Deep 26 1 12 9 49

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Appendix C - Raw macroinvertebrate results for each site at the eight locations

Group Common Name Taxa N o r t N h o : r S t N h h o a : r l D t N l e h o o e - r w p E t E a h a s - s t E t E : a : a S s S s h t h t S a : a : o l D l D u l e l e t S o e o e h o w p w p - u E t S a h o s - u t E t S : a h o S s : u h t S t S a : h h o l D a : u l e l D t S o e l e h o w p o e - u w p W t W e h e s - s t W t W : e : e S s S s h t h t N a : a - o l D l D r l e l e t N o e o e h o w p w p - r W t e h s - t W : e S s h t a : l D l e o e w p Amphipoda Side-swimmers Ceinidae 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 Cnidaria Hydra Hydridae 10 0 0 0 0 10 0 0 0 0 0 10 30 180 10 0 Coleoptera Predacious Diving Beetles Dytiscidae 10 0 0 0 0 0 0 0 0 0 0 0 30 0 20 0 Coleoptera Predacious Diving Beetle larvae Dytiscidae (larva) 0 0 10 0 20 0 0 0 0 0 0 0 50 0 20 0 Coleoptera Scavenger Beetles Hydrophilidae 0 0 0 0 0 0 10 0 0 0 0 0 0 0 0 0 Cordylophora Colonial Hydroids Clavidae 820 20 10 1690 10 90 0 0 0 0 0 10 10 210 30 90 Decapoda Freshwater Shrimp Atyidae 1 1 0 40 10 10 0 10 0 1 0 0 0 10 0 1 Decapoda Yabbies Parastacidae 1 0 10 0 1 1 1 0 10 0 1 1 1 1 20 0 Diptera Biting Midges Ceratopogonidae 130 30 70 70 90 110 70 50 210 20 50 60 230 10 420 80 Diptera Non-biting Midges Chironominae 80 50 40 30 120 380 50 70 190 50 60 40 70 80 190 50 Diptera Non-biting Midges Tanypodinae 10 0 440 0 490 10 50 30 520 90 820 340 110 80 320 60 Ectoprocta Bryozoa Bryozoa 0 0 60 10 30 0 10 0 100 20 0 30 30 10 10 10 Ephemeroptera Mayflies Caenidae 1120 10 200 50 150 30 180 0 10 0 0 10 230 30 890 10 Ephemeroptera Mayflies Ephemeroptera (immature) 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 Epiproctophora Dragonflies Epiproctophora (immature) 0 0 0 0 0 0 0 10 0 0 0 0 0 0 0 0 Hemiptera Water Boatmen Corixidae 370 1 750 100 730 170 660 20 810 20 430 270 300 150 420 20 Hemiptera Backswimmers Notonectidae 20 90 60 70 100 160 60 110 30 40 0 10 20 10 30 110 Mollusca Freshwater Limpets Ancylidae 0 0 20 0 0 0 0 0 0 0 0 0 0 0 0 0 Oligochaeta Worms Oligochaeta 30 10 60 10 250 90 30 20 610 100 80 30 240 10 0 90 Ostracoda Seed Shrimp Ostracoda 2180 0 1760 980 14160 1300 17540 310 3760 60 1240 7980 6900 210 6140 190 Trichoptera Caddiesflies Ecnomidae 0 0 0 0 0 30 10 0 10 0 0 0 0 20 10 10 Trichoptera Caddiesflies Leptoceridae 20 0 30 10 30 40 180 80 80 0 60 20 0 30 40 110 Zygoptera Damselfies Coenagrionidae 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0

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Appendix D – Vegetation quadrat raw data

GHD | Report for Mallee Catchment Management Authority - Lake Wallawalla Vegetation and Aquatic Survey, 3136086 Quadrat no. 1234567891011 Date 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 Assessor Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Recently Recently Recently Receding receded ‐ Recently receded ‐ Recently receded ‐ Recently Water depth zone Inundated (mudflat) dry Inundated receded dry Inundated receded dry Inundated receded Water depth 151015001000100 Saplings <2 m no. 00000000000 Saplings <2 m ht. 00000000000 Seedlings <0.25 m (no.) 00000000000 Water cover 100 40 0 100 0 0 100 0 0 100 0 Bare ground cover 0 55 60 0 60 50 0 60 65 0 70 Litter cover 01101102205 CWD cover 00000000000 Cryptogram cover 00000000000 Bryophyte cover 00000000000 Native cover 0 5 40 1 40 50 0 40 35 0 25 Introduced cover 00000000000 Water depth zone Green 2Blue 3 Purple 4 Green 2Blue 3 Purple 4 Green 2Blue 3 Purple 4 Green 2Blue 3

Bird Bird footprints footprints Bird and and Bird Notes footprints! droppings droppings droppings Species PFG Status Ammannia multifloraTdav00000200100 Austrobryonia micranthaTdar00000000000 Bergia trimera Tdrv00000000000 Centipeda nidiformisATlr00000000000 Elacholoma prostrataARpr00000000000 Eleocharis acuta ATe00000000000 Eucalyptus camaldulensisAtw00000000000 Glossostigma sp. ATl00000000000 Haloragis aspera Tda00000.1000200.1 Heliotropium sp. Tdr*00000000000 Limosella australis ATl00000000002 Medicago polymorphaTdr*00000000000 Medicago sp. Tdr*00000000000 Mimulus repens ATl00000000000 Potamogeton sp. ARf00010000000 Sporobolus mitchellii Tda 0 5 40 0 40 50 0 40 30 0 25 Stemodia florulenta Tda00000000000 Underwater stoloniferousARp00000000000 SPECIES RICHNESS 01112201303 Quadrat no. 12 13 14 15 16 17 18 19 20 21 22 Date 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 17/04/2018 Assessor Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Recently Recently Recently Recently receded ‐ Receding receded ‐ Receding receded ‐ Receding receded ‐ Water depth zone dry Inundated (mudflat) dry Inundated (mudflat) dry Inundated (mudflat) dry Inundated Water depth 015102000150015 Saplings <2 m no. 00000000000 Saplings <2 m ht. 00000000000 Seedlings <0.25 m (no.) 000000150000 Water cover 0 100 30 0 100 0 0 100 0 0 100 Bare ground cover 70 0 65 45 0 80 40 0 85 70 0 Litter cover 1001201150110 CWD cover 00000000000 Cryptogram cover 00000000000 Bryophyte cover 00000000000 Native cover 15 5 5 50 0 20 45 5 15 30 0 Introduced cover 00010010110 Water depth zone Purple 4 Green 2Blue 3 Purple 4 Green 2Blue 3 Purple 4 Green 2Blue 3 Purple 4 Green 2

Bird Eucalypt Bird footprints seedlings in footprints Bird Bird and quadrat and Bird Notes footprints droppings! droppings <2cm droppings droppings Species PFG Status Ammannia multiflora Tda v 10010000000 Austrobryonia micrantha Tda r 0000000.10000 Bergia trimera Tdr v 0001000.10000 Centipeda nidiformis ATl r 10010010000 Elacholoma prostrata ARp r 00000000000 Eleocharis acuta ATe 055202005000 Eucalyptus camaldulensis Atw 00000000000 Glossostigma sp. ATl 00000000000 Haloragis aspera Tda 10010100000 Heliotropium sp. Tdr * 00000000000 Limosella australis ATl 00000000000 Medicago polymorpha Tdr * 00000010110 Medicago sp. Tdr * 0000.10000000 Mimulus repens ATl 0000000.10000 Potamogeton sp. ARf 00000000000 Sporobolus mitchellii Tda 15 0 0 45 0 0 40 0 15 30 0 Stemodia florulenta Tda 0.10000020000 Underwater stoloniferous ARp 00000000000 SPECIES RICHNESS 51170271220 Quadrat no. 23 24 25 26 27 28 29 30 31 32 33 Date 17/04/2018 17/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 Assessor Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Recently Recently Recently receded ‐ Recently Recently Recently receded ‐ Recently Recently Water depth zone receded dry Inundated receded receded Inundated receded dry Inundated receded inundated Water depth 00100010001000 Saplings <2 m no. 11000000000 Saplings <2 m ht. 165210000000000 Seedlings <0.25 m (no.) 00000000000 Water cover 00100001000010000 Bare ground cover 90 55 0 95 75 0 90 50 0 75 30 Litter cover 15011011011 CWD cover 00000000000 Cryptogram cover 00000000000 Bryophyte cover 00000000000 Native cover 10 40 0 5 25 1 10 50 0 25 70 Introduced cover 01000010000 Water depth zone Blue 3 Purple 4 Green 2Blue 3 Purple 4 Green 2Blue 3 Purple 4 Green 2Blue 3 Purple 4

Bird Bird Bird Bird and footprints footprints Bird and footprints Bird kangaroo and and Bird kangaroo and Bird Notes footprints faeces droppings droppings droppings faeces droppings droppings Species PFG Status Ammannia multiflora Tda v 00000005000.1 Austrobryonia micrantha Tda r 00.1000000000 Bergia trimera Tdr v 00000.1000000 Centipeda nidiformis ATl r 00.1001000001 Elacholoma prostrata ARp r 00000000000 Eleocharis acuta ATe 00000000000 Eucalyptus camaldulensis Atw 0.10.1000000000 Glossostigma sp. ATl 00000000000 Haloragis aspera Tda 10100.10100001 Heliotropium sp. Tdr * 00.1000000000 Limosella australis ATl 00000000000 Medicago polymorpha Tdr * 00000010000 Medicago sp. Tdr * 00.1000000000 Mimulus repens ATl 00000000000 Potamogeton sp. ARf 00000000000 Sporobolus mitchellii Tda 24005250104502570 Stemodia florulenta Tda 00000000000 Underwater stoloniferous ARp 00000000000 SPECIES RICHNESS 37023122014 Quadrat no. 34 35 36 37 38 39 40 41 42 43 44 Date 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 Assessor Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Recently Recently Recently Recently receded ‐ Recently receded ‐ Receding receded ‐ Recently Water depth zone Inundated inundated dry Inundated receded dry Inundated (mudflat) dry Inundated receded Water depth 150015001010100 Saplings <2 m no. 00000000000 Saplings <2 m ht. 00000000000 Seedlings <0.25 m (no.) 00000000000 Water cover 100 0 0 100 0 0 100 60 0 100 0 Bare ground cover 080600602503580090 Litter cover 0110130011001 CWD cover 00000000000 Cryptogram cover 00500100000 Bryophyte cover 00000000000 Native cover 12035240451510510 Introduced cover 00000000002 Water depth zone Green 2Blue 3 Purple 4 Green 2Blue 3 Purple 4 Green 2Blue 3 Purple 4 Green 2Blue 3 Kangaroo Bird Bird Bird and rabbit Bird droppings, footprints Bird and footprints droppings, footprints abundant and kangaroo and RRG 10 m and Bird Medicago Notes droppings faeces droppings away droppings droppings seed Species PFG Status Ammannia multiflora Tda v 00100100100 Austrobryonia micrantha Tda r 00000000000 Bergia trimera Tdr v 00100000000 Centipeda nidiformis ATl r 00000000000 Elacholoma prostrata ARp r 00100000000 Eleocharis acuta ATe 00001000000 Eucalyptus camaldulensis Atw 00000000000 Glossostigma sp. ATl 01000000000 Haloragis aspera Tda 01001000.10.100 Heliotropium sp. Tdr * 00000000000 Limosella australis ATl 00000000000 Medicago polymorpha Tdr * 00000000002 Medicago sp. Tdr * 00000000000 Mimulus repens ATl 00000000000 Potamogeton sp. ARf 00000000000 Sporobolus mitchellii Tda 02035040450510010 Stemodia florulenta Tda 00000000000 Underwater stoloniferous ARp 10020010050 SPECIES RICHNESS 13413212312 Quadrat no. 45 46 47 48 49 50 51 52 53 54 55 Date 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 Assessor Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Recently Recently Recently receded ‐ recently receded ‐ Recently receded ‐ Recently Recently Water depth zone dry Inundated receded dry Inundated receded dry Inundated receded receded Inundated Water depth 010001000150020 Saplings <2 m no. 00000000000 Saplings <2 m ht. 00000000000 Seedlings <0.25 m (no.) 00000000000 Water cover 0100001000010000100 Bare ground cover 45 0 90 70 0 80 40 0 85 40 0 Litter cover 10510110120 CWD cover 00000000000 Cryptogram cover 00000000000 Bryophyte cover 00000000000 Native cover 55 1 5 30 0 20 60 5 15 55 5 Introduced cover 00100110010 Water depth zone Purple 4 Green 2Blue 3 Purple 4 Green 2Blue 3 Purple 4 Green 2Blue 3 Purple 4 Green 2

Bird Bird Bird Bird footprints footprints footprints footprints Bird and and and and Bird Notes droppings droppings droppings droppings droppings droppings Species PFG Status Ammannia multiflora Tda v 50010050000 Austrobryonia micrantha Tda r 00000000000 Bergia trimera Tdr v 1000.10010000 Centipeda nidiformis ATl r 00010010000 Elacholoma prostrata ARp r 00000000000 Eleocharis acuta ATe 100005151515 Eucalyptus camaldulensis Atw 00000000000 Glossostigma sp. ATl 00000000000 Haloragis aspera Tda 01100010010 Heliotropium sp. Tdr * 00000000000 Limosella australis ATl 00100100000 Medicago polymorpha Tdr * 00100110010 Medicago sp. Tdr * 00000000000 Mimulus repens ATl 00000010000 Potamogeton sp. ARf 00000000000 Sporobolus mitchellii Tda 500 5300155500550 Stemodia florulenta Tda 00000000000 Underwater stoloniferous ARp 00000000000 SPECIES RICHNESS 41440481141 Quadrat no. 56 57 58 59 60 61 62 63 64 65 66 Date 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 18/04/2018 Assessor Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Recently Recently Receding Recently Recently Receding receded ‐ Water depth zone Inundated receded Inundated (mudflat) receded Inundated Inundated receded Inundated (mudflat) dry Water depth 30150015501500 Saplings <2 m no. 00000000000 Saplings <2 m ht. 00000000000 Seedlings <0.25 m (no.) 00000000000 Water cover 100 0 100 0 0 100 100 0 100 0 0 Bare ground cover 04008560009009085 Litter cover 01505100252015 CWD cover 00001000000 Cryptogram cover 00005000000 Bryophyte cover 00000000000 Native cover 10 45 5 10 25 5 5 10 0 10 10 Introduced cover 01002001000 Water depth zone Blue 3 Purple 4 Green 2Blue 3 Purple 4 Green 2Blue 3 Purple 4 Green 2Blue 3 Purple 4

Bird Bird droppings, footprints Bird and Euc cam 3 m and kangaroo Floating Euc Bird Bird Notes away droppings faeces cam litter droppings footprints Cracking clay Species PFG Status Ammannia multiflora Tda v 00000000000 Austrobryonia micrantha Tda r 00000.1000000 Bergia trimera Tdr v 00001000000 Centipeda nidiformis ATl r 00001000000 Elacholoma prostrata ARp r 00000000000 Eleocharis acuta ATe 10355101550000 Eucalyptus camaldulensis Atw 00000000000 Glossostigma sp. ATl 00000000000 Haloragis aspera Tda 110001000010 Heliotropium sp. Tdr * 00000000000 Limosella australis ATl 00000000000 Medicago polymorpha Tdr * 01002001000 Medicago sp. Tdr * 00000000000 Mimulus repens ATl 00000000000 Potamogeton sp. ARf 00000000000 Sporobolus mitchellii Tda 000020001001010 Stemodia florulenta Tda 00000000000 Underwater stoloniferous ARp 00000000000 SPECIES RICHNESS 23117112021 Quadrat no. 67 68 69 70 71 72 Date 18/04/2018 18/04/2018 18/04/2018 18/04/2028 18/04/2018 18/04/2018 Assessor Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Tim Wills Recently Recently receded ‐ inundated? ‐ Water depth zone Inundated Inundated dry Inundated Inundated dry Water depth 15501510 Saplings <2 m no. 000001 Saplings <2 m ht. 0000095 Seedlings <0.25 m (no.) 000000 Water cover 100 100 0 100 95 0 Bare ground cover 00350560 Litter cover 005055 CWD cover 000000 Cryptogram cover 000000 Bryophyte cover 000000 Native cover 15601240 Introduced cover 000000 Water depth zone Green 2Blue 3 Purple 4 Green 2Blue 3 Purple 4 Cracking clay, bird and kangaroo Kangaroo Notes faeces Mudflat faeces Species PFG Status Ammannia multiflora Tda v 000000 Austrobryonia micrantha Tda r 000000 Bergia trimera Tdr v 000000 Centipeda nidiformis ATl r 000000 Elacholoma prostrata ARp r 000000 Eleocharis acuta ATe 000000 Eucalyptus camaldulensis Atw 000005 Glossostigma sp. ATl 000000 Haloragis aspera Tda 050101 Heliotropium sp. Tdr * 000000 Limosella australis ATl 000000 Medicago polymorpha Tdr * 000000 Medicago sp. Tdr * 000000 Mimulus repens ATl 000000 Potamogeton sp. ARf 000000 Sporobolus mitchellii Tda 00600235 Stemodia florulenta Tda 000.1000 Underwater stoloniferous ARp 110000 SPECIES RICHNESS 122113 GHD Level 8 180 Lonsdale Street T: 61 3 8687 8000 F: 61 3 8687 8111 E: [email protected]

© GHD 2018 This document is and shall remain the property of GHD. The document may only be used for the purpose for which it was commissioned and in accordance with the Terms of Engagement for the commission. Unauthorised use of this document in any form whatsoever is prohibited. 3136086- 77758/https://projects.ghd.com/oc/Victoria1/lakewallawallaaquati/Delivery/Documents/3136086_RP T_A_Lake Wallawalla Limnological Survey.docx Document Status Revision Author Reviewer Approved for Issue Name Signature Name Signature Date A Peter Lind 14/6/18

B P. Lind A. Holmes A. Holmes 8/8/18 T. Wills

P. Lind A. Holmes A. Holmes 24/09/18 T. Wills www.ghd.com