Darling–Baaka water science projects

About the project

On 10 February 2024, reports were received of tens of dead adult golden perch and hundreds of fish struggling at the water surface in the Darling–Baaka River at Menindee. Golden perch continued to die with daily mortalities appearing to peak around 26 February. The number of dead and distressed fish steadily declined after that, with no further reports of dead golden perch at Menindee by early April. The estimated total number of fish affected was in the low thousands. 

The Weir 32 Science Program was established in June 2024 to investigate the cause of the golden perch deaths and to further understand the impacts of previous mass fish deaths on the water quality and sediments of the Menindee weir pool. Multiple scientific studies were conducted as a part of the program, which involved sampling and analysing sediments, water quality, fish and decapod parasites, decapod communities, groundwater, dissolved oxygen and thermal stratification. 

What we found

The findings of the Weir 32 Science Program suggest that the extreme parasite loads driven by poor water and sediment quality, an inability to escape the weir pool and the preference of golden perch to eat and forage in the benthic zone led to their deaths in February and March 2024. Find more information in the summary report below.

Summary report

The summary report combines the findings of all projects conducted as part of the Weir 32 Science Program. The report includes background information, a timeline of previous mass fish deaths, and summaries of investigations into:

• dissolved oxygen and stratification dynamics within the Menindee weir pool
• groundwater – surface water connectivity and influence of benthic sediments on water quality in the Menindee weir pool
• the impacts of mass fish deaths on long-term water quality
• effects of mass fish deaths on decapod communities
• initial water quality, cyanobacteria and sediment analysis during the 2024 golden perch deaths
• parasitism of fish and decapods in the Menindee weir pool
• physical-chemical properties and microbial communities of the sediment of the Darling River near Menindee.
   

Read about the program: Summary of the Weir 32 Science Program

Technical reports 

Read the technical reports below:

• Report 1 - Timeline and causes of recent fish deaths in the Menindee weir pool  
• Report 2 - The impacts of mass fish deaths on water quality in the Menindee weir pool  
• Report 3 - The impacts of mass fish deaths on decapod communities in the   Menindee weir pool  
• Report 4 - Parasitism of golden perch in the Menindee weir pool  
• Report 5 - Dissolved oxygen and thermal stratification in the Menindee weir pool
• Report 6 - Assessing groundwater - surface water connectivity and influence of benthic sediments on water quality in the Menindee weir pool  
• Report 7 - Water quality, cyanobacteria and sediment analysis for the Menindee weir pool  
   

About the project

This report presents the outcomes of a collaborative research project aimed at understanding and predicting thermal stratification and dissolved oxygen dynamics in the Menindee weir pool. The project was undertaken as a research collaboration between the department, the University of Technology Sydney and the University of Sydney and builds on years of field data collection and modelling expertise in river systems.

Thermal stratification occurs when water in a river or weir pool separates into layers of different temperatures. This layering can prevent oxygen from circulating throughout the water column, particularly isolating the bottom layer (hypolimnion) from surface oxygen exchange. When stratification persists and the bottom layer becomes depleted of oxygen, a sudden mixing event, such as a change in flow or weather, can cause oxygen levels to drop sharply across the entire water column. These events are a known trigger for mass fish deaths, which have occurred in the Lower Darling–Baaka River in recent years.

Overall, the project delivers a practical and scientifically grounded tool for managing oxygen risks in the Menindee weir pool. It represents a significant step forward in predictive modelling for river health and provides a foundation for future enhancements and broader application across NSW river systems.

Read the report: Developing a thermal stratification model for the Menindee weir pool 
 

In response to recommendations FR8(c) and FR10 the department implemented a program to expand the water quality monitoring network to ensure we have the right data to inform better water management decisions.

WaterNSW has installed 3 new multi-depth monitoring pontoons in the Darling–Baaka River at Menindee. In addition, 4 fixed depth sensors were upgraded to self-cleaning multi parameter water quality sensors to reduce maintenance costs and data errors. 

The water quality parameters being monitored now include dissolved oxygen, pH, turbidity, electrical conductivity, chlorophyll, phycocyanin and water temperature. 

The existing dissolved oxygen monitoring network has also been expanded to include an additional 40 monitoring sites to fill data gaps across the Murray–Darling Basin. This real time data will assist in identifying and assessing the level of risk to aquatic ecosystems, managing extreme water quality events and to measure the success of any water management actions.
 

Find the monitoring data at: WaterInsights - WaterNSW
 

About the project

The NSW Water Quality Monitoring Framework (the Framework) is being developed to help organise, improve and share water quality monitoring data for NSW rivers and streams. The project is due for completion in June 2026.

Water quality data in NSW is collected by a variety of agencies to monitor river and stream health. However, there is no singular repository or catalogue of water quality monitoring projects in NSW, and data can be difficult to access or is available in various formats and standards. 

This means information with the potential to assist future water quality monitoring and modelling program design, incident responses or policy decisions may not be accounted for by agencies or accessible by the public. 

The aim of the Water Quality Monitoring Framework is to provide:

• guidance and governance for the department and sharing of state government water quality data.
• direction on standards for agencies and organisations to follow in water quality monitoring data collection, management and sharing.
• strategic direction on the use of water quality monitoring data by state government agencies to report long term trends in water quality, respond to water quality incidents and provide data to the public through digital platforms. 

How will it work?

Organising and sharing data

As part of the Framework, we are developing a centralised catalogue of high-quality water quality data on an open data platform to organise and improve access to water quality monitoring datasets collected by government agencies. A prototype of the catalogue will be available on NSW SEED – the NSW Government’s central resource for accessing and sharing environmental data - at the end of the project.

The Framework will also provide a governance model to support the sharing, organization, and quality assurance of data through the catalogue. This model will clarify roles and responsibilities of water quality monitoring agencies and appoint an agency to assist in the day-to-day running and curation of the data catalogue and help water quality data collection agencies to share high quality data. 

Improving standards and protocols for data collection, management and transfer

The Framework will provide documentation on the most appropriate standards and guidelines for agencies and organisations to follow for the collection, management and sharing of water quality monitoring data and metadata. This will help to standardise and improve the quality of data collected and shared and enable better exchange of data.

The Framework will also provide data custodians with a process to share their data through NSW SEED and access quality assurance support from the integrating authority. 

Strategic direction

Understanding where, how, what for, by whom and when water quality data is used is crucial to success in achieving data informed outcomes and improvements in water quality of rivers and streams.

The Framework will outline the landscape of water quality monitoring in NSW and signpost where data is used in statutory reporting commitments and agency obligations and how it should be made available to the public. The Framework will also explain how water quality data is used in real-time monitoring by agencies, incident notification processes and enacting water quality incident response plans.

Furthermore, the Framework will provide recommendations for the improvement of water quality monitoring data collection, management and sharing in NSW. 

What about other water quality data?

At present, the Framework is focused only on water quality data monitoring that allows environmental assessment of river and stream health. However, in the future, the Framework may be adopted or expanded to water quality datasets related to groundwater, coastal and marine systems, drinking water quality, pollution incidents and emerging contaminants in the future.

What if I have data to share?

If you have a water quality dataset that you would like to share or publish please contact the NSW Water Quality Monitoring Framework at water.enquiries@dcceew.nsw.gov.au.