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Selected Area: Edward/Kolety-Wakool

The Wamba Wamba or Wemba Wemba, and Perrepa Perrepa or Barapa Barapa are the traditional owners of the Edward/Kolety-Wakool River system – a large anabranch of the Murray River in the southern Murray-Darling Basin, Australia. The system is a complex network of interconnected streams in a productive agricultural landscape. Our work in this system focuses on understanding how native fish, vegetation, water quality and processes that support and sustain aquatic food webs, are influenced by targeted environmental watering actions.

Image: Backwater of the mid Wakool River. Photo credit: Robyn Watts, Charles Sturt University

We are honoured to work on the ancestral lands of the Wamba Wamba or Wemba Wemba, and Perrepa Perrepa or Barapa Barapa People. We recognise their unique ability to care for Country and their deep spiritual connection to it. We honour Elders past and present whose knowledge and wisdom has ensured the continuation of culture and traditional practices. We are committed to genuinely partner and meaningfully engage with Traditional Owners and Aboriginal communities to support the protection of Country, the maintenance of spiritual and cultural practices and their broader aspirations in the 21st century and beyond.

About the Edward/Kolety-Wakool catchment

The Edward/Kolety-Wakool River system begins in the Millewa Forest and flows north, and then northwest, before discharging back into the Murray River. It is a complex network of interconnected streams, ephemeral creeks, flood-runners and wetlands including the Edward River, Wakool River, Yallakool Creek, Colligen-Niemur Creek and Merran Creek. It includes several small intermittent and ephemeral creeks of ecological significance such as Tuppal, Jimaringle, Cockran and Gwynne’s Creeks.

The flow regimes of rivers in the Edward/Kolety-Wakool river system have been significantly altered by river regulation. Natural flows in this system are strongly seasonal, with higher flows typically occurring from July to November. Flow regulation has reduced the frequency and magnitude of winter high flows, including extreme high flow events and average daily flows during the winter period. Under regulated conditions, flows in the Edward River and tributaries remain within the channel, whereas during unregulated high flows there is connectivity between the river channels, floodplains and several large forests.

Map showing the main rivers and tributaries in the Edward/Kolety-Wakool river system

Why this area is important

The Edward/Kolety-Wakool river system is important for its high native species richness and diversity, including threatened and endangered fish, frogs, mammals, and riparian plants. It is listed as an endangered ecosystem, as part of the ‘aquatic ecological community in the natural drainage system of the lower Murray River catchment’ in New South Wales. Barmah-Millewa Forest, Koondrook-Perricoota Forest and Werai Forest make up the NSW Central Murray Forests Ramsar site.

This system also plays an important ecological role in connecting upstream and downstream ecosystems in the mid-Murray River. The multiple streams and creeks in this system provide important refuge and nursery areas for fish and other aquatic organisms, and adult fish regularly move between this system and other parts of the Murray River.

The area supports a productive agricultural community, has a rich and diverse Indigenous history, and supports both active and passive recreational uses such as fishing, bird-watching and bush-walking. Many Aboriginal nations maintain strong connections to the country, including the Wamba Wamba or Wemba Wemba, Perrepa Perrepa or Barapa Barapa, and Yorta Yorta. The Werai Forest is in the process of conversion to an Indigenous Protected Area.

Our approach

The many rivers, creeks and flood-runners in the Edward/Kolety-Wakool river system have very different hydrological regimes. This means that we need to monitor a range of sites to assess ecological responses to environmental watering in different parts of the system. Over the three years of the Flow-MER project, our team will undertake field monitoring at sites throughout the Edward/Kolety-Wakool River system, continuing to build on the five years of data collected during Long Term Intervention Monitoring (LTIM) program.

We are taking a whole of ecosystem approach to evaluate the responses to environmental watering in this system. We monitor physical habitat, water quality, ecosystem metabolism, riverbank and aquatic vegetation and fish. The results from this program have been used to inform decision-making for water for the environment. The results from the seven years of the LTIM and Flow-MER projects will be used to build predictive models that relate environmental indicators to discharge or other flow related parameters such as water velocity, or the extent of riverbank inundation under different flows. Through collaboration with managers and other stakeholders these models can be used to help predict what would happen under different environmental watering actions and flow regimes in this system.

We also monitor changes in wetland vegetation communities, as well as modelling river flows and wetland hydrology, investigating inundation area (extent of flow/flooding), frequency and water depth. From the monitoring data we gather we then analyse and evaluate interactions and relationships between biodiversity responses and environmental watering actions. This knowledge can then be used to inform the adaptive management of environmental water delivery. Our activities include:

Collection of field data

Our team collects data on stream metabolism, water quality, the diversity and abundance of riverbank and aquatic vegetation, fish spawning, recruitment and adult fish populations. Some of our field data are from loggers (for example water quality loggers which record dissolved oxygen and temperature in the river continuously) and other data is collected from regular field trips to sites where we do the monitoring.

Image caption: Monitoring aquatic vegetation. Photo credit: Robyn Watts, Charles Sturt University.

Analysis of data to link ecological response to flow

Ecosystem responses to water for the environment are evaluated in two ways:

  1. Indicators that respond quickly to flow (e.g. water quality) are evaluated for each environmental watering actions. Responses to the discharge including environmental water, are compared to responses to the discharge without the environmental water.
  2. Indicators that respond over longer time frames (e.g. vegetation, fish populations) are evaluated for their response to the longer-term environmental watering regime. Responses over multiple years in reaches that have received environmental water, are compared to responses in reaches that have received no environmental water or a different pattern of environmental water.
Image caption: The Wakool River in winter 2017 during an environmental watering action. Photo credit: Sascha Healy, NSW Department of Planning, Industry and Environment.

Collaborate with partners and communicate our findings

We undertake activities that bring managers, the community and scientists together to foster relationships and provide local people with the opportunity to participate and contribute their knowledge and expertise to the project. Through a partnership with Yarkuwa Indigenous Knowledge Centre, Traditional Custodians are collaborating on our turtle and vegetation research projects. Research on fish spawning is being undertaken in partnership with the Edward/Kolety-Wakool Angling Association. Engagement with other community members occurs through workshops facilitated in collaboration with community organisations including the Western Murray Land Improvement Group and the Wakool River Association.

Image caption: Community field day on the Edward River, December 2019. Photo credit: Robyn Watts, Charles Sturt University.

Conduct research

We are undertaking an integrated research and community engagement project to address physical, ecological, and social questions about the Edward River. This research will inform the future delivery of Commonwealth environmental water to the Edward River and the management of environmental water in relation to the Werai Forest, which is part of the NSW Central Murray Forests Ramsar site and is in the process of conversion to an Indigenous Protected Area.

Image caption: Undertaking research on freshwater turtles. Photo credit: Yarkuwa Indigenous Knowledge Centre.
Setting drift nets to study fish spawning in the Edward River Photo credit: Robyn Watts, Charles Sturt University
Thule lagoon. Photo credit: Julia Howitt

Current activities

We monitor a set of indicators to answer questions about the outcomes of Commonwealth environmental water in the Edward/Kolety-Wakool river system. These indicators provide the Commonwealth Environmental Water Office and other water managers with information to help inform the planning of environmental watering actions.

We are also undertaking an integrated research and community engagement project in partnership with community organisations to increase our knowledge about the Edward/Kolety-Wakool river system.

Hydrology

We use data from stream flow gauges and information from water accounts to determine the contribution of Commonwealth environmental water to changes in flow and water level in the river system. This information underpins our analysis of the ecological responses to environmental flows.

Hydrographs of Yallakool Creek and three reaches of the Wakool River from May 2017 to June 2018. The portion of the discharge shaded black is attributed to the delivery of Commonwealth Environmental Water. The blue shaded sections indicate the timing of environmental watering actions.

Hydraulic habitat

The hydraulic conditions in the river channel are created by the interaction between channel morphology and flow. A more diverse hydraulic environment provides a greater range of habitats for aquatic biota. Although river discharge is usually expressed as a volume of water per day (ML/day), information on the hydraulic habitat can be more useful to describe the conditions experienced under different flows because aquatic plants and animals respond to properties of flow such as depth and velocity.

We have developed hydraulic models for sixteen reaches in the Edward/Kolety-Wakool river system and we use these models to calculate the area of inundation under different flows, duration of inundation of plants on the riverbank, and the velocity of water during the spawning season of fish.

Modelled water velocities and riverbank inundation under an operational flow and an environmental flow in Yallakool Creek.
Surveying water velocity and depth in the Wakool River Photo credit: Robyn Watts, Charles Sturt University

Water quality

We monitor dissolved organic carbon, nutrients, dissolved oxygen, pH, and water temperature at 19 sites through the Edward -Wakool river system. Water quality monitoring can inform us about the input of carbon and nutrients into the river system following riverbank inundation during environmental watering actions. We also monitor water conditions during poor water quality events such as algal blooms or hypoxic blackwater events, to help water managers decide if there are opportunities to deliver environmental water to help mitigate poor water quality outcomes.

Monitoring water quality in the Wakool River. Photo credit: Robyn Watts, Charles Sturt University

Ecosystem metabolism

Ecosystem metabolism refers to the production of food for fish and water bugs through photosynthesis (gross primary production) and the breakdown of that food to release the energy it contains (ecosystem respiration). These processes are the basis for the food web that links all animals and plants in the river system.

We use continuous measurements of dissolved oxygen concentrations at ten sites in the Edward/Kolety-Wakool river system to calculate daily estimates of gross primary production and ecosystem respiration. These data provide information about stream metabolism and how it is modified by the delivery of Commonwealth environmental water.

Contribution of Commonwealth environmental water to carbon production (Kg C/day) during a watering action in spring /early summer 2014-15. Zones 1, 3 and 4 received Commonwealth environmental water. CEW – Commonwealth Environmental Water

Riverbank and aquatic vegetation

Riverbank and aquatic vegetation provides food and habitat for aquatic animals, and can help to stabilise riverbanks and reduce erosion. Environmental water plays an important role in supporting these plant communities.

We monitor riverbank and aquatic vegetation at sixteen sites in the Edward/Kolety-Wakool river system. Our monitoring is showing that vegetation responds positively to environmental water. Between 2014 and 2018 there was consistently higher species richness at sites that received environmental water compared to sites that received none or minimal environmental water. However, the unregulated flood in 2016 killed off most of this vegetation, and the system is still recovering from this event. The delivery of environmental water in winter can maintain aquatic plants and prevent frost damage to aquatic vegetation.

Above and below –Response of aquatic vegetation to Commonwealth environmental water in Yallakool Creek Photo credit: Robyn Watts, Charles Sturt University

Fish spawning

Environmental water has been delivered to support fish outcomes in the Edward/Kolety-Wakool river system every year since 2010. We are monitoring fish spawning at twenty sites using light traps and drift nets that are deployed overnight once a fortnight during spring and summer. The results are used to determine the role of Commonwealth environmental water in supporting fish breeding and recruitment.

Over the five years of the LTIM program we detected 16 fish species (including four introduced species) as larvae or eggs at these sites in the Edward/Kolety-Wakool river system. In 2016, eggs of Silver perch were detected for the first time in this system. The spawning of Silver perch may have been due to increased velocities or increased variability of flows in some reaches during environmental watering actions.

Silver perch and Silver perch eggs from the Edward/Kolety-Wakool system. Photo credit: Charles Sturt University

Fish recruitment

The early stage of the life of a fish is when the highest mortality occurs. Recruitment (survival of eggs/larvae to young-of-year life-history stage) is a fundamental process required to sustain fish populations.

Monitoring of fish recruitment is undertaken between February and March each year to target fish hatched that year (young-of-year, YOY) or the previous year (1+ individuals). In 2018-19 Murray cod YOY and 1+ fish were detected in highest numbers since LTIM monitoring commenced in 2015. Along with the presence of 1+ silver perch in the system, this suggests that the Edward/Kolety-Wakool fish assemblage is showing positive signs of recovery since the 2016-17 unregulated flood and hypoxic blackwater event that resulted in large scale fish kills in the southern Murray-Darling Basin.

Juvenile Murray cod (Maccullochella peelii) from Yallakool Creek. Photo credit: John Trethewie, Charles Sturt University

Fish populations

One of the principal aims of the Basin Plan is to improve native fish communities throughout the Murray-Darling Basin. An improving native fish community would demonstrate that environmental flows and other management actions are contributing to the environmental processes that can lead to long-term improvements in river ecosystem.

We monitor the fish community through an annual intensive survey in the Wakool River using electrofishing and fyke nets. Collected fish are counted, measured and weighed before being released back into the river. This is a continuation of monitoring that began through the LTIM Project and provides data for basin-scale analyses of fish assemblage.

In addition, we will monitor fish populations at 20 sites throughout the Edward/Kolety-Wakool river system in year 3 (2022) of the Flow-MER project. These 20 sites have been monitored seven times since 2009 and the Flow-MER project will contribute to this long-term dataset. Data from this broad-scale survey, coupled with data collected from the intensive annual survey, will enable us to examine long-term change trajectories of the native fish population.

Electrofishing in the Wakool River. Photo Credit: Robyn Watts, Charles Sturt University

Communication and engagement

We organise events and activities to communicate the findings of the project and provide local people with the opportunity to be involved in monitoring and research. Results from project activities are shared through; collaborative research projects in partnership with community organisations, presentations to the Edward/Kolety-Wakool Environmental Water Reference Group, workshops, field days, and through local newspaper articles and newsletters. We contribute to on-going adaptive management of environmental water in the system by working with water managers and other stakeholders to develop annual and long-term watering plans for the system.

Sharing knowledge at a community field day on the Edward River, December 2019. Photo credit: Robyn Watts, Charles Sturt University

Integrated research project

We are undertaking an integrated research and community engagement project to address physical, ecological, and social questions about the Edward River. The research is being undertaken in partnership with Yarkuwa Indigenous Knowledge Centre, the Edward/Kolety-Wakool Angling Association and the Western Murray Land Improvement Group. We will examine how managed flows in the Edward River and the operation of Stevens Weir influence lateral connectivity, physical form and ecological processes (river productivity, wetland plant emergence and survival, turtle movement and condition, and fish spawning). Social research is integrated with the biophysical research to enable stakeholders to share their perspectives about water for the environment and their involvement in monitoring, research and water management.

Turtle research team Photo credit: Liticia Ross, Yarkuwa Indigenous Knowledge Centre
We are using drones to study changes in the condition of riverbanks Photo credit: Robyn Watts, Charles Sturt University

What we’ve learned

Lateral and longitudinal connectivity

Environmental watering actions in the Edward/Kolety-Wakool river system are managed within regular operating ranges, as advised by river operators, to avoid third party impacts. The types of flows that can be achieved with environmental water under current operating ranges are in-channel base-flows and small freshes.

Environmental water delivered as base flows in winter is critical to maintain longitudinal connectivity and prevent cease-to-flow conditions in the Yallakool-Wakool and Colligen-Niemur River systems. Base flows provide opportunities for fish movement and seed dispersal, as well as maintaining critical overwinter habitat for turtles and other animals that have small home ranges.

Small freshes delivered under normal operating rules can result in small increases in lateral connectivity, with variation among sites due to differences in river shape. These flows have resulted in some benefits to water quality, river productivity, vegetation and the fish community.

A flow trial undertaken in August-September 2018 to examine the outcomes of a slightly higher peak discharge than current operating rules highlighted:

  • there was increased lateral connectivity within the river system compared to flows delivered under normal operating rules.
  • the importance of planning flows with local land holders, agencies and community members.
  • the need to have access to alternative water delivery arrangements (such as via the Murray Irrigation network) in the event that Water NSW infrastructure is unable to meet target flow rates.
  • that inundation of some low-level private bridges may occur under higher flows. Due to careful planning and consultation this did not limit landholders access to their properties during the trial.
Image caption: Inundated backwater of the Wakool River on Bookit Island during the peak of the August-September 2018 flow trial. Photo credit: Robyn Watts

Winter flows

Winter environmental flows maintain longitudinal connectivity and prevent disconnection of the smaller tributaries into a series of disconnected pools. Winter flows have improved water quality in the lower Wakool River, as well as increasing river productivity and assisting with the movement of native fish throughout the system. The impact of providing winter flows for other plants and animals that were not monitored, such as freshwater mussels and Murray crayfish, is yet to be explored.

Image caption: The Wakool River in winter 2016 during an operational shutdown (no environmental water). Photo credit: Sascha Healy, NSW Department of Planning, Industry and Environment.

Water quality and productivity outcomes

Commonwealth environmental water has maintained good water quality and not resulted in any adverse outcomes in the system. Under some circumstances, refuge flows provided from good water quality sources during unregulated floods can be effective in mitigating the risk of hypoxic (low oxygen) water conditions.

Small freshes delivered under normal operating rules can result in small increases in lateral connectivity and provide small increase in river productivity. Flows through Millewa Forest have been demonstrated to provide a productivity boost into the Edward/Kolety-Wakool River system. The forest of the NSW mid-Murray forests can also play an important role in providing food to the rivers and creeks that are connected to them if environmental water is delivered at a cooler time of year to avoid poor water quality.

Image caption: Refuge flows being delivered to the Edward River upstream of Deniliquin during the unregulated flood event and associated hypoxic conditions in November/December 2016. Credit: Commonwealth Environmental Water Office.

Vegetation outcomes

Water for the environment has improved the condition of riverbank and aquatic vegetation. There was consistently higher numbers of species in river reaches that received environmental water, than in those reaches that received no or minimal environmental water. However, a large unregulated flood in late 2016 considerably reduced the aquatic vegetation in this system. Flows provided since 2016 have been used to assist with the recovery of in-stream aquatic plants throughout the system.

  • Providing a slow rate of recession to flows enables native water plants to avoid being stranded and drying out.
  • The delivery of environmental water in winter can maintain aquatic vegetation and can protect plants from frost damage and improve their rate of recovery the following spring frost damage to plant rhizomes, but the recovery will be over multiple years.
Image caption: Aquatic vegetation in the Wakool River in summer 2015 after four consecutive years of environmental watering. Photo credit: Robyn Watts, Charles Sturt University

Native fish outcomes

Commonwealth environmental water has supported fish movement and maintained habitat for fish.

The overall health of the Edward/Kolety-Wakool fish community decreased from 2015 to 2019 following poor water quality and associated fish deaths during an unregulated flood in 2016. The fish community is currently in a state of recovery. A slow recovery of the Murray cod population appears to be underway, and this system also appears to be a nursery area for Silver perch, with periods of high flow in summer seeming to trigger spawning. The absence of Golden perch spawning or recruitment in this system highlights the importance of Golden perch migration into this system from the Darling and/or the Murray systems.

A number of flow-related mechanisms may contribute to the recovery of fish populations at a local scale. These include:

  1. the persistence of refuge habitat at low flows or during adverse water quality events.
  2. the presence of diverse in-channel and off-channel habitats.
  3. opportunities for movement that enable the re-distribution of individuals and promote emigration and immigration.

The results of native fish movement and survival following the unregulated flood in 2016 has emphasised the importance of providing connectivity between the River Murray and anabranch systems. It is vital that connectivity is maintained prior to, during and after these events to allow fish to disperse and seek refuge and then return to the anabranch after the event has passed.

Image caption: Trout cod caught in Yallakool Creek on 31 May 2019. Photo credit: John Trethewie, Charles Sturt University

Latest updates

For additional Flow-MER activities and reports on the Edward/Kolety-Wakool, please visit the Commonwealth Environmental Water Office (CEWO) website.

Aquatic plants in the Wakool River. Photo credit: Robyn Watts, Charles Sturt University
Flooding in the Wakool River during the 2016 during an unregulated flood. Photo credit Robyn Watts

Our team

Scientists from Charles Sturt University, La Trobe University, NSW Department of Primary Industries, NSW Department of Planning Industry and Environment, and Streamology Pty Ltd undertake the ongoing monitoring in the Edward/Kolety-Wakool river system.

An integrated research and community engagement project investigating links between flows and water quality, vegetation, turtles, fish spawning and biodiversity in the Edward River is being undertaken in collaboration with Yarkuwa Indigenous Knowledge Centre, the Edward/Kolety-Wakool Angling Association and the Western Murray Land Improvement Group.

Professor Robyn Watts

Robyn is an aquatic ecologist and ecohydrologist at Charles Sturt University and leads the Edward/Kolety-Wakool team. She undertakes interdisciplinary research in partnership with biophysical scientists, social scientists and community organisations to help inform the adaptive management and restoration of river ecosystems.

Dr Nicole McCasker

Nicole is a freshwater ecologist at Charles Sturt University and researches the ecology of freshwater fish during their early life stages, as well as the functional and conservation ecology of freshwater mussels in altered rivers. She has a soft spot for data wrangling and data visualisation.

Dr Xiaoying (Sha sha) Liu

Sha sha is a Research Fellow and environmental scientist at Charles Sturt University. She has a research background in environmental chemistry and management responses to water pollution, land use change and climate change, with a focus on cycling of nutrients and carbon in freshwater environments.

John Trethewie

John is a Senior Technical Officer at Charles Sturt University with expertise in freshwater fish ecology and aquatic fauna survey techniques. He is currently involved in monitoring early life history and recruitment of native fish.

Associate Professor Catherine Allan

Catherine, an Associate Professor at Charles Sturt University, undertakes social and institutional research in natural resource and environmental management contexts. She has especial interest in adaptive and collaborative management of surface and ground water, soil and vegetation.

Dr Jason Thiem

Jason is a Fisheries Scientist with the NSW Department of Primary Industries. Jason’s current research program is focussed on the abiotic drivers of fish movement, spawning and recruitment within the Murray-Darling Basin, with a strong focus on riverine connectivity

Dr Meaghan Duncan

Meaghan is a Freshwater Fish Ecologist with the NSW Department of Primary Industries with expertise in molecular ecology and freshwater fish ecology. Her current research focuses on using genetic techniques to provide essential information to enable effective management of a wide range of fish species.

Dr Daniel Wright

Daniel is a Fisheries Scientist at the NSW Department of Primary Industries. He currently investigates fish community responses to environmental flows in the Murray-Darling Basin and is broadly interested in applied ecological research that facilitates fisheries management decisions.

Dr Geoff Vietz

Geoff is the Principal Scientist and Director of the consulting company Streamology, as well as being a Senior Research Fellow at the University of Melbourne. He has extensive experience on geomorphology, environmental flows, ecohydraulics, physical form monitoring and waterway management.

Neil Sutton

Neil is an Environmental Scientist at the consultancy Streamology. He has extensive experience in monitoring river channel morphology, riparian vegetation and coastal/foreshore change. His passion lies in using data to tell rich, evocative stories.

Professor Nick Bond

Nick is Director of the Centre for Freshwater Ecosystems at La Trobe University. His research focuses on patterns and processes in aquatic ecosystems, with a strong focus on the effects of hydrology, climate and catchment influences.

Dr James Van Dyke

James is a Senior Lecturer in Biomedical Sciences at La Trobe University. His research focuses on the physiological links between environmental change and wildlife declines, and he has a broad background in conservation physiology of vertebrates.

Sascha Healy

Sascha is an Environmental Water Manager based in the Lower Murray-Darling with the Biodiversity and Conservation Division of the Department of Planning, Industry and Environment. She has expertise in project management, ecological monitoring and aquatic and floodplain plant identification. Sascha monitors aquatic vegetation response to flows to help inform and prioritise where environmental water should be delivered.

Julia Howitt

Julia was an environmental chemist and member of the Edward/Kolety-Wakool research team from 2010 to 2020. Sadly, Julia passed away in April 2020. The legacy of her contribution to our understanding of carbon dynamics and water quality (especially hypoxic blackwater) in the Murray-Darling Basin is ongoing. We will continue to use long-term datasets that Julia helped establish, to predict outcomes of environmental watering actions and assist the management of river ecosystems.

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This page contains information specific to the Murrumbidgee Commonwealth Environmental Water Office (CEWO) Monitoring, Evaluation and Research Project. For further information about water use in the Mid-Murray catchment, please click here to visit the CEWO website.

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