The Menindee Lakes were modified during the 1950s and 1960s to provide Broken Hill with a reliable water supply and to supply water for irrigation to NSW, Victoria and South Australia. On average 426 gigalitres of water is lost in evaporation from the lakes system each year. A series of investigations has been undertaken by the NSW Government since 1995 to identify potential structural works and management changes to improve the efficiency of the Menindee Lakes and to reduce evaporation losses.
The Menindee Lakes system is located on the Darling River, about 200 kilometres upstream of the junction of the Darling and Murray Rivers. The lakes represent a significant natural, cultural and economic resource for Australia.
The large wetland ecosystem within the Menindee Lakes supports a diverse range of native flora and fauna - when full, there is more bird species found here than at Kakadu.
Prior to the construction of the Menindee Lakes Storage Scheme, the lakes naturally filled during high river flows and subsequently receded to form a series of pools. High evaporation rates at times dried the lakes out. Structures were built to enhance the ability of the lakes to store and release water and include a number of weirs, regulators, levees and channels.
Menindee Lakes is made up of nine lakes, but generally water is stored in the four larger lakes - Lake Pamamaroo, Lake Wetherell, Lake Menindee, and Lake Cawndilla.
The lakes have a nominal full supply volume of 1,730 gigalitres and can be surcharged to hold up to 2,050 gigalitres during floods.
Water savings measures
The competing demands of cultural heritage, environmental values and efficient water storage make the Menindee Lakes one of the most complex systems to manage in Australia.
Ongoing work has been undertaken since the end of the 20th century involving multiple negotiations and studies. This includes the Darling River Water Savings project and agreements to progress options that will save water and protect environmental and cultural heritage values while ensuring supply for communities in NSW, Victoria and South Australia.
The way forward - water savings opportunities
There has been significant public debate about the need for achieving water savings to reduce the impacts of the on-going purchase of water licences to implement the Murray-Darling Basin Plan. NSW has remained committed to investigating options for the improved management of the Menindee Lakes, but the final option chosen needs to recognise the enormous water supply benefits to NSW, Victoria and South Australia, and the natural environmental values of the Menindee Lakes.
In December 2013, the Australian and NSW Governments announced funding for project planning and detailed design work.
The investigations announced in December 2013, aim to implement a suite of measures designed to improve the management of Menindee Lakes. The package includes infrastructure works, operating rule changes and drought security water supply infrastructure for Broken Hill, which, if agreed, would realise annual water savings of up to 80 gigalitres and improve the storage efficiency of the lakes. The operation rules for the Menindee Lakes will require agreement of New South Wales, Victoria and South Australia and the project will be subject to consultation with the local conmmunities.
Menindee Lakes – detailed options planning?
The Australian and NSW Governments have undertaken numerous studies into improving the efficiency of the Menindee Lakes. Based on these studies, a basic scope of works and operational changes that could allow the lakes to be operated in a way that achieves significant water savings, was agreed to in December 2013.
The next step is to undertake detailed project planning and costings, stakeholder consultation and design work which will provide a basis for undertaking the infrastructure and operational changes at the lakes.
While the Australian and NSW Governments have agreed to a basic scope of potential changes, no final decision has been made on any infrastructure or operational changes. These will be subject to the outcome of the work and stakeholder consultation.
What is the Australian Government funding being spent on?
The Australian Government is providing up to $800,000 to the NSW Government to:
- prepare detailed plans
- undertake environmental, heritage and social assessments and technical reports
- undertake stakeholder consultation.
Will stakeholders be consulted and who is leading on the consultation?
Stakeholders will be consulted during the development of this phase of the Menindee Lakes Project. The NSW Government will manage the stakeholder consultation process.
No final decisions will be made on infrastructure or operational changes to the lakes until the outcome of the further work and stakeholder consultation has been done.
When will work on the planning project be completed?
The work is scheduled to be undertaken before the end of 2014, with the final technical reports expected to be received by 30 November 2014.
At this stage, it is too early to predict when on-ground works will commence because they are dependent on completion of the current body of work, the environmental, heritage and planning approval processes, the public tendering of the works and the lakes being sufficiently empty to allow work to occur.
What are the benefits of improving the efficiency of the Menindee Lakes?
It is a priority for NSW to recover water for the environment through infrastructure investment and improving the operations of the Menindee Lakes. It is expected that this work will result in reduced evaporation. The saved water will help meet the environmental water required under the Basin Plan and reduce the impact of the Basin Plan on irrigation communities. Based on current modelling, the infrastructure and operational changes are projected to save around 80 gigalitres per year of water that would otherwise evaporate from the lakes.
What is the scope of the infrastructure works and potential changes to the operations of the lakes that has been agreed to date?
NSW does not support the use of groundwater as the regular supply for Broken Hill - but will consider it to supplement supply in times of drought.
This current project will investigate implementation issues associated with these changes.
Surface water infrastructure to be constructed includes:
- Morton Boolka regulator
- Enlarged Lake Menindee regulator
- Drainage channel for Lake Menindee
- Darling anabranch regulator
- Flood mitigation for Menindee township.
Changes to operational arrangements for the Menindee Lakes Scheme:
- Broken Hill drought water supply arrangements:
- water savings, contributions to bridging the gap and Sustainable Diversion Limits adjustments under the Basin Plan
- further work to be undertaken including:
- further modelling of New South Wales' preferred Lake Cawndilla surcharging regime, related changes to the Menindee Lakes operational rules and options for addressing any negative third party impacts
- assessing the potential environmental watering requirements for maintenance of the environmental values of the Menindee Lakes System (including documentation of, and justification for, environmental values in the context of the operation of the lakes since their construction, future environmental water requirements and social or economic impacts)
- assessment of the Lower Darling to identify potential flood runners and ‘breakouts' at high flows
- understanding of the interaction between the savings from the project at Menindee Lakes and the potential for further savings from the 198 GL additional flows coming into the lakes as a result of the Basin Plan
- defining the potential for extra savings that might be achieved by increasing the demand on the Menindee Lakes to supply environmental assets on the Murray River or by allowing flexibility in delivering flows to South Australia.
In addition, changing the operational rules for the Menindee Lakes will increase the water savings possible with the new infrastructure. This includes changing the threshold volume of water that changes the control of the lakes between the MDBA and NSW Government (the 640/480rule).
Operational rule changes require the agreement of the Australian Government and Murray-Darling Basin governments through the Murray-Darling Basin Ministerial council.
For more information, go to the Department of Environment (Australian Government).