The Lower Lakes Independent Science Review

The way the Lower Lakes are managed is contested. Some stakeholders question whether historically the Lakes were fresh prior to construction of the barrages and whether removing the barrages would result in an increase in water for the region. In late 2019, it was agreed to review the science and clarify the appropriate approach to river management for the region.

The Advisory Committee on Social, Economic and Environmental Sciences (ACSEES) is an important source of independent, strategic advice to the Murray–Darling Basin Authority (MDBA). They recommended the appointment of an independent panel of scientific experts to:

• review the existing science relating to the management of the Lower Lakes and Coorong
• identify advantages and/or implications of called for changes, and
• note the knowledge gaps to fill to accurately plan for future climate change.

In 2019, the independent panel was established with 5 independent experts to undertake the review. In 2020, the independent panel examined hundreds of studies on the Lower Lakes, Coorong and Murray Mouth and consulted with almost 100 scientists and technical experts. They reviewed many aspects, ranging from climate, hydrology, hydrodynamics, geomorphology, palaeoecology, ecosystems and environmental watering.

Review findings

In 2020, the independent panel delivered their findings. The panel found that while some knowledge gaps were evident, the science of the Coorong, Lower Lakes and Murray Mouth was well understood. The panel outlined that the available research findings are consistent and that the Lower Lakes are being managed appropriately.

Key findings include:

The Lower Lakes were largely fresh prior to European settlement.

• Despite some claims that the Lower Lakes were naturally saline, the weight of evidence points to the main body of the Lower Lakes being largely fresh prior to European settlement. This is informed by palaeoecological records, water balance estimates, hydrological and hydrodynamic modelling, and traditional knowledge of the Ngarrindjeri People and anecdotal evidence of early explorers and colonists.
• The pre-development long-term average annual inflow from the Murray River is more than 13,000 gigalitres (GL). This volume would fill the lakes on average more than 8 times a year.
• Upstream development has reduced the river inflow by about half, resulting in more frequent incursion of seawater into the Lower Lakes.
• The barrages were built in 1940 in response to these changes, isolating the Coorong and the sea from the Lower Lakes.

Removing the barrages would have significant ecological and socio-economic impact.

• Without the barrages, the freshwater values in the Lower Lakes cannot be maintained.
• This will significantly change the ecological character of the Ramsar-listed site, which is a wetland of international importance and which we have an international obligation to maintain.
• This will also impact traditional owner values and other socio-economic values that are reliant on a healthy Coorong, Lower Lakes and Murray Mouth system.

Removing the barrages would not result in any water savings if targets informed by science and modelling and envisaged under the Basin Plan are to be met.

• The additional Murray River inflow secured under the Basin Plan has been shown to enhance the ecological outcomes, building resilience in the system and providing some inflow during dry years.
• Environmental water is managed for multiple benefits, where water is reused as it flows down the river, to sustain a healthy system across the entire Basin. Most of the environmental water reaching the Lower Lakes has also benefited upstream assets.
• Removing the barrages would not result in any water savings if targets informed by science and modelling and envisaged under the Basin Plan are to be met.

Under climate change, the management of the Coorong, Lower Lakes and Murray Mouth would become increasingly challenging.

• Sea level rise would alter the hydrodynamics of the Coorong and Murray Mouth, and cause more seawater to flow into the Lower Lakes. Evaporation from the Lakes would be higher. Therefore, more Murray River inflow would be needed to achieve Coorong, Lower Lakes and Murray Mouth outcomes. However, catchment runoff in the southern Murray-Darling Basin is projected to decline under climate change.
• There are gaps in the knowledge of the biophysical impact under climate change, and the social, environmental and economic vulnerabilities. There is a need to develop adaptation options, not just for the Coorong, Lower Lakes and Murray Mouth, but as part of the whole Murray–Darling Basin system.

Moving forward

The MDBA supports evidence-based decision making around water management and we are committed to continually improving our knowledge base. This independent review helps governments make informed decisions and provides additional assurances to Basin communities. It also helps us plan for the future. We will use the results of the review to further support our current work.

Read the media release.

Review Team

The review was led by Dr Francis Chiew of the Commonwealth Scientific and Industrial Research Organisation (CSIRO).

Dr Francis Chiew has more than 25 years’ experience in research, teaching and consulting, and in science leadership and management. Dr Chiew is globally recognised for his expertise in hydroclimate, hydrological modelling and integrated river basin management, and his research is widely adopted and cited. Dr Chiew and his team have led many major hydroclimate initiatives and water resources assessment projects, informing water resources planning and adaptation in Australia and globally. Dr Chiew is a member of several global and national water expert committees including lead author of 2 assessment reports for the United Nations Intergovernmental Panel on Climate Change.

Supporting panel members:

Ms Jennifer Hale is an aquatic ecologist with expertise in wetland, riverine and estuarine systems with over 30 years of experience in the management of aquatic ecosystems. She has extensive knowledge of the Ramsar Convention and its application to the management of wetlands in Australia. She was one of 3 leaders of the technical review panel for Ramsar documentation and was involved in the development of guidance on implementation of the Convention including on the definition of Limits of Acceptable Change (LAC) and change in ecological character. Jennifer has acted as an advisor on Ramsar wetlands for State and Australian governments and has recently completed a review of the effect of large-scale drivers on ecological character.

Dr Michael Reid is a senior lecturer in Geography and Planning at the University of New England. He has more than 20 years of experience in research focusing on understanding pattern and process in floodplain and river ecosystems across a range of spatial and temporal scales and on understanding how human activities impact river ecosystems. This focus requires interdisciplinary research and expertise in palaeoecology, food web ecology, floodplain and aquatic vegetation community ecology, geomorphology, hydrology and ecohydrology. Michael is the current president of the Australian Freshwater Sciences Society.

Dr Klaus Joehnk is leading the Modelling Water Ecosystems team in CSIRO Land and Water. He has over 20 years of experience in research and consultancy on hydrodynamic and water quality modelling of lakes and rivers. Klaus and his team are leading work on combining hydrodynamic and water quality modelling with satellite remote sensing of inland waters for operational short-term forecasting of water quality and building integrated simulation tools for assessing ecological outcomes of inland water management. Klaus serves on the editorial board for Ecological Informatics Journal and is a committee member of the Australian Water Association.

Dr Ian Webster is an Independent consultant. Dr Webster is an expert in physical oceanography, coastal lakes and processes, hydrodynamic modelling and biogeochemical modelling. Dr Webster was a senior principal research scientist in CSIRO until he retired in 2012. Dr Webster is well known in Australia and overseas for his scientific leadership of multidisciplinary projects that support the management of lakes, rivers and estuaries. Dr Webster has a deep knowledge of the Lower Lakes, having developed the hydrodynamic model for the Coorong for assessing the effectiveness of salinity amelioration measures.

Background to the region

The Coorong, Lower Lakes and Murray Mouth is a dynamic region covering around 142,500 hectares in South Australia. It marks the end of the Murray–Darling Basin with the River Murray flowing into the Great Australian Bight, having passed through Lake Alexandrina and Lake Albert – a connected terminal lake (the Lower Lakes), the Murray estuary and finally the Murray Mouth.

The region is used for many purposes, including agriculture, urban development, conservation, recreation, water storage and extraction, it is also an important social, spiritual and cultural location for the traditional owners of the land, the Ngarrindjeri people. 

It is a Ramsar Wetland of International Importance and is home to a diverse range of freshwater, estuarine and marine habitats. The native plants, animals and migratory birds are unique, not just within the Murray–Darling Basin, but worldwide. The region is the only point of entry and exit for fish that move between freshwater and marine habitats and is the only pathway to export salt from the Murray–Darling Basin.

History of water management for the Coorong, Lower Lakes and Murray Mouth

From the earliest days of settlement along the lower reaches of the river, there were strong representations from landowners for the construction of barrages. The primary reason for their construction was to keep the water fresh in the lower reaches of the River Murray, as well as Lake Albert and Lake Alexandrina.

Before the Lower Lakes barrages were built, tidal effects and the intrusion of seawater occurred during periods of low flow into the Lower Lakes and in the River Murray, up to 250 km upstream from its mouth. Although this effect was a normal part of the variation of the lower river system, the impacts were further intensified by increased regulation and upstream diversion of water that decreased periods of high flow along the lower Murray and reduced overall flows to the Lower Lakes.

In 1931, the then River Murray Commission decided – after extensive investigation – to construct 5 barrages to help manage lake levels and improve water quality in the lower Murray and Lower Lakes system. Work on the barrages commenced in 1935 and was completed in 1940. South Australia's Engineering and Water Supply Department undertook the work, with the costs shared equally by the governments of South Australia, Victoria, New South Wales and the Commonwealth.

The barrages

The 5 barrages, Goolwa, Mundoo, Boundary Creek, Tauwitchere and Ewe Island were completed in 1940 and are located between Lake Alexandrina and the Coorong, where the River Murray completes its 2,530 km journey and flows into the Great Australian Bight.

The main purpose of the barrages is to prevent saline waters of the Coorong lagoons and Murray Mouth estuary entering the lakes and the River Murray. The barrages also help to:

• limit 'reverse flows' of seawater into the lakes during storms, high swells and high tides
• stabilise and raise the river level to provide irrigation (by gravitation) along the reclaimed river flats between Wellington and Mannum
• manage releases to control water levels, water quality and environmental outcomes in the lower lakes, the Coorong and the Murray Mouth
• concentrate releases to the ocean to a small area by scouring a channel for navigation during low flows
• provide a supply of water that can be pumped to Adelaide and the south-eastern corner of South Australia, and
• enable social, recreational and cultural uses of the Lower Lakes.

Although the barrages are considered to be Murray–Darling Basin Authority assets, the South Australian state government is responsible for working collaboratively with the Murray–Darling Basin Authority to manage and maintain all water management assets in South Australia (including the barrages, locks and weirs).