A year in the Murrumbidgee catchment: 2023–24

Waterbird breeding, native fish nesting and movement, endangered waterbirds and frogs were the focus of managed environmental flows in 2023–24.

Key outcomes

Under average rainfall and flow conditions, environmental water managers worked with partner agencies and stakeholders to coordinate the delivery of water for the environment to:

• support the nesting requirements of trout cod and Murray cod in the Murrumbidgee River and Yanco Creek systems
• maintain distribution of the endangered southern bell frog and Australasian bittern in key areas of the Lowbidgee floodplain
• improve fish movement by managing several opportunistic fish pulses, which incorporated the removal of the 3 lower Murrumbidgee weirs.

Catchment conditions

During the 2023–24 year, the Murrumbidgee catchment experienced an easing of La Niña weather conditions resulting in near average rainfall and below average temperatures.

The average rainfall combined with high starting dam levels resulted in general and high security licences being 100% allocated. Supplementary water was also accessed during unregulated flow events and the release of water from dams to create airspace.

Infrastructure unavailability constrained the scale of floodplain watering in the Lowbidgee, so environmental water use focussed on in-channel events to benefit native fish breeding and movement opportunities.

Partnering with Aboriginal peoples

Water for Country is environmental water use planned by the Department of Climate Change, Energy, the Environment and Water and Aboriginal people to achieve shared benefits for the environment and cultural places, values and/or interests.

In the 2023–24 water year, environmental water managers:

• worked collaboratively with Nari Nari Tribal Council to deliver cultural and environmental outcomes throughout the Gayini wetlands through deliveries of water for the environment
• worked closely with Mutthi Mutthi to deliver multiple in stream flow events, focussed on native fish breeding and then connectivity flows, to allow fish to move along the length of the regulated river and into the lower reaches of the Murrumbidgee River from the Murray system
• worked closely with Wiradjuri to maximise the outcomes of water for the environment by eliminating exotic fish and promoting revegetation within Coonancoocabil Swamp
• attended and contributed to a gathering of Traditional Owners of the Murrumbidgee, supported by the Commonwealth Environmental Water Holder and facilitated by the Murray Lower Darling Rivers Indigenous Nations. The discussions centred on addressing issues and concerns collaboratively for the benefit of Country. A key focus was fish movement, with acknowledgement of improvements in the mid-Murrumbidgee. Specific strategies and actions were discussed to enhance fish movement into the lower system and continue to work collaboratively.

The Water for the Environment Program partnered with the Reconnecting River Country Program to:

• host 4 meetings with the First Nations Reference Group. These meetings focused on discussing technical aspects of the program including the options evaluation framework , which was assessed according to cultural criteria to evaluate flow options.
• coordinate On-Country assessments in collaboration with local nations and local Aboriginal land councils. These assessments identified culturally and environmentally significant places that would benefit from increased flow options; however, without improved access to Country, the full benefits for Aboriginal communities will not be realised.

Watering aims

Under predicted wet to very wet weather and water availability, the Murrumbidgee Environmental Water Advisory Group developed its Annual environmental water priorities in the Murrumbidgee catchment 2023–24.

Objectives for the use of water for the environment were to:

• provide foraging and breeding habitat for waterbirds, including threatened species, in the Lowbidgee
• provide stable Murrumbidgee River and Yanco Creek flows during the cod nesting season to maximise nesting success
• maintain native fish, turtle and southern bell frog core habitat areas
• increase river connectivity with the Lowbidgee lakes and maximise fish passage by slowing rates of recession after dam releases.

When very wet conditions occurred, environmental water managers used adaptive management strategies to maintain river functions and enhance opportunities for plants and animals to breed, move and thrive.

High flow conditions eased along the Murrumbidgee River during late winter and regulated flow conditions were ongoing throughout the year due to average rainfall. The floodplain wetlands of Yanga, North Redbank and the mid-Murrumbidgee were adequately watered without environmental water use, due to residual flood water and minor overbanking in early winter. The Gayini (Nimmie-Caira) wetlands and the Western Lakes were the only Lowbidgee floodplain systems that required water for the environment.

Water delivery

This table and chart provide a summary of 478,616 megalitres of water for the environment delivered in the Murrumbidgee catchment during the 2023–24 watering year.

Figures were accurate at the date of publishing but may be adjusted. Watering event numbers in the table and chart relate to location numbers marked on the map.

Notes:  CEW = Commonwealth licensed environmental water; EWA = environmental water allowance accrued under the water sharing plan; NSW = NSW licensed environmental water; Other = landholder; TLM = The Living Murray.

Outcomes

In 2023–24, environmental water managers worked collaboratively with the Nari Nari Tribal Council, and the Commonwealth Environmental Water Holder (CEWH) to deliver 59 gigalitres of water for the environment across the Gayini (Nimmie-Caira) wetlands. This watering event started in mid-September and extended through to late April to support Australasian bittern breeding and fledging.

Working closely with the CEWH, Murray–Darling Basin Authority and WaterNSW, 384 gigalitres of CEWH, The Living Murray project and New South Wales environmental water was initially used to create stable river levels during the Murray cod and trout cod nesting season.

Throughout summer and autumn, a number of fish pulses were created to maximise fish movement and floodplain connectivity outcomes for native fish. Elevated base flows were also provided in the lower reaches of the river to enhance fish habitat during the hotter months.

In partnership with Murrumbidgee Irrigation, NSW National Parks and Wildlife Services, NSW Crown Lands, Murray–Darling Wetland Working Group and the CEWH, 3.3 gigalitres of Commonwealth and Murray–Darling Wetland Working Group environmental water was delivered to prioritised wetlands across the Murrumbidgee Irrigation Area. These wetlands provided habitat for several threatened species including Australasian bitterns and brolgas.

Case study: bidgee brolga bonanza

Within days of environmental flows inundating the Tuckerbil Swamp, a Ramsar-listed wetland near Leeton, local bird watchers reported that 25 brolgas had moved in.

Several months later brolga numbers peaked with 30 birds counted during routine waterbird surveys.

This is known as a ‘flocking event’, where many birds of the same species assemble for weeks or months, then eventually pair up and disperse into surrounding breeding areas for nesting.

Ongoing waterbird surveys throughout late winter and spring will reveal how long the brolgas used the site and whether they nested at Tuckerbil Swamp or other regional environmental water sites such as Fivebough Swamp or Turkey Flats.