Murrumbidgee catchment

Magpie geese at Tori Lignum Swamp, North Redbank. Photo: Erin Lenon, CEWO

The Murrumbidgee River contains diverse and rich natural environments. Its waterways are a source of water supply for domestic use, extensive irrigated agriculture production, tourism, recreational activities, and the cultural values and practices of local Aboriginal Traditional Owners.

The Murrumbidgee region is home to the vast and nationally significant Lower Murrumbidgee River (Lowbidgee) Floodplain and the mid-Murrumbidgee River Wetlands. The Lowbidgee floodplain covers about 200,000 hectares and includes some of the largest lignum wetlands in New South Wales. It is an important bird breeding site, particularly for the royal spoonbill, great egret, straw-necked ibis, Australian white ibis and glossy ibis.

The Lower Murrumbidgee floodplain also contains the Gayini Nimmie-Caira project area, consisting of over 80,000 hectares of land that support a range of wetland-dependent species, including threatened species such as the Australian painted snipe, southern bell frog and the Australasian bittern. The Gayini Nimmie-Caira Enhanced Environmental Water Delivery project (the Gayini Nimmie-Caira Project) was established to protect, maintain and enhance the Nimmie-Caira environment, relax constraints to water delivery and help “bridge the gap” to Sustainable Diversion Limits in the Murrumbidgee. Following the 2013 purchase of Gayini Nimmie-Caira lands (with funding provided by the Commonwealth to NSW under a Heads of Agreement) in 2018 the NSW Government, through an open tender process, selected The Nature Conservancy in a partnership with Aboriginal and scientific groups to manage the Gayini Nimmie-Caira project area, which will provide:

ongoing environmental and indigenous cultural heritage protection;
indigenous engagement and participation; and
sustainable land use.

The Gayini Nimmie-Caira project was completed in 2019 on time and under budget. More information on the Gayini Nimmie-Caira project can be found at: The Nimmie-Caira Project.

The mid-Murrumbidgee River Wetlands are nationally significant, and support river red gum forests and blackbox woodlands that provide habitat to threatened species, again including the southern bell frog and the Australasian bittern.

The Murrumbidgee region is also home to the internationally significant Ginini Flats wetlands in the upper catchment, and the Ramsar listed Fivebough and Tuckerbil Swamps within the Murrumbidgee Irrigation Area.

Delivery of environmental water to date (as of May 2023)

Setting nets at Goorogool Lagoon, November 2019. Photo: Gaye Bourke, Charles Sturt University

Since 2009, Commonwealth environmental water has been delivered to sites across the Murrumbidgee catchment targeting both in-stream and wetland habitats to support their recovery or maintain their health.
Some of the significant contributions Commonwealth environmental deliveries have made to date, include:

maintaining critical refuge habitats for water dependent animals including waterbirds, native fish, birds, frogs and turtles. This includes protecting listed threatened animals from further decline or possible local extinctions;
re-establishing the threatened southern bell frog populations in the mid-Murrumbidgee (locally extinct for 40 years) and at Yanga National Park (not detected between 2013 and 2017);
re-establishing important native wetland plant communities in the mid-Murrumbidgee that had been lost from wetlands;
supporting successful breeding outcomes and maintaining important habitat for over 30 waterbird species;
restoring the natural watering frequency of wetland sites in the mid-Murrumbidgee, Lowbidgee floodplain and Junction Wetlands to support their recovery; and maintain and/or improve their ecological condition;
maintaining the ecological character of internationally listed Ramsar wetlands, Fivebough and Tuckerbil, and supporting the waterbirds that depend on them;
supporting the spawning and growth of eight native fish species into local populations;
reducing the impact on native fish and other water dependent animals from very poor water quality (lethally low dissolved oxygen concentrations) in response to natural flooding in 2016 and 2021;
avoiding further fish deaths in Lowbidgee weir pools caused by very poor water quality that developed in response to low flows in the river and high temperatures associated with drought in 2019.
Triggering and supporting numerous waterbird breeding events across the valley including several consecutive large-scale breeding events of more than 18,000 pairs of predominantly straw-necked in the Lowbidgee. Other species that also successfully bred included egrets, spoonbills, herons, cormorants, darters, swans, threatened blue-billed and freckled ducks, brolgas and Australasian and little bitterns.
Successfully recovering the threatened southern bell frog population in the Lowbidgee to pre-Millennium drought numbers after the population came close to becoming locally extinct during the drought.
Supporting the spawning and recruitment of golden perch on the Yanga National Park floodplain and providing flows to assist fish passage between the Murrumbidgee and Murray.

The Murrumbidgee Valley experienced dry conditions from early 2017 up until a transition to wetter conditions from early 2020. With the continuance of wet conditions and high water resource availability into 2022-23, the primary focus for use of Commonwealth water for the environment is to maintain, and where possible improve the health and resilience of aquatic ecosystems. This will be achieved by targeting in-channel fish movement; facilitating connection between the floodplain and river channel for fish and nutrient dispersal and larger scale wetland and floodplain inundation to improve habitat condition. Due to prolonged periods of high unregulated flows, Commonwealth water for the environment was not required until December 2022. To date, an estimated 202,822 ML of Murrumbidgee Regulated Commonwealth environmental water has been delivered and 6672 GL of Lowbidgee Supplementary Allocation License (LBG SAL) delivered. Details of deliveries are as follow.

Gayini Nimmie-Caira Wetlands

A total of ~72GL* has been delivered to Gayini-Nimmie Caira wetlands in response to a large-scale waterbird breeding event. Water for the environment was delivered to successfully maintain waterbird breeding grounds (rookery) inundation levels and water quality at Bala, Telephone and Suicide and extend flows to western Gayini-Nimmie Caira sites including Avalon Dam and Swamp, Loorica, Kieeta and Kia Lakes and Kia Swamp.

It is important to maintain inundation levels on the back of bird breeding events because if the water levels in their rookery rise too high, nests can flood or if they drop too much, adult birds may abandon their nests and feral animals like foxes and pigs, can gain access to the rookeries. And if the water quality deteriorates in the rookeries, the birds are at risk of diseases such as avian botulism or blue green algae outbreaks in rookery sites. Extra monitoring was employed by Charles Sturt University, under the Monitoring and Evaluation Program (funded by CEWH) to record bird numbers, chick growth and survival rates and provide real-time water level and water quality readings to inform water delivery requirements.

Water for the environment supported breeding of an estimated 102,000 nesting pairs of straw-necked ibis at Bala Rookery for the third consecutive year and supported over 4,000 pairs of nesting adult pelicans at Kieeta Lake. Over 52 different water bird species have been observed, including the threatened Freckled Duck, threatened Australasian Bittern, great crested grebes, Australasian grebes, black swans, night herons, black winged stilts and white-bellied sea-eagles...the list goes on. Many of these water birds rely on floods and full wetlands to breed.

Low DO Refuge and Native Fish Passage Flows in Lowbidgee (in-channel)

A total of 238 GL* (combination of CEW, EHG and TLM) has been delivered in-channel to successfully improve low dissolved oxygen levels and provide native fish passage from Maude weir to the River Murray between December 2022 to May 2023.

In early December 2022, dissolved oxygen levels at Maude, Redbank and Balranald weirs, in the Lower portion of the Murrumbidgee (Lowbidgee), had declined in response to the prolonged period of high unregulated flows in 2022. Low dissolved oxygen is usually brought about after extreme amounts of rain which carries organic matter into rivers, which is then broken down by bacteria in the water. The process can strip the oxygen from the water, turning it hypoxic and in extreme cases causing mass fish deaths. Widespread riverine flooding in the Murray Darling basin saw large numbers of native fish die in the Murray and Darling Rivers in 2022 as toxic water lowered oxygen levels in the water. With use of water for the environment in the Murrumbidgee this was the first flooding event in at least a decade where the same did not happen in the Murrumbidgee. Dissolved oxygen levels improved in the Lowbidgee and there was no record of fish kills.

Despite improvements in dissolved oxygen, blue-green algae numbers were on the rise with amber and green alerts in place at Redbank and Balranald weirs, respectively, in February 2023. The Murrumbidgee Regulated Water Source Water Sharing Plan provides for end of system flows to be 180ML in April. This would see the river drop from ~6000ML/d very quickly to 180ML/d. Given the blue-green algae abundance, planned low flows and summer temperatures, water for the environment was ordered to target up to 3000ML/d at Balranald weir to continue to support water quality and keep the river free flowing over weirs for continued fish passage. Catchment-wide rainfall in April led to rainfall rejections and surplus flows in the catchment. Opportunistically, water for the environment was directly ordered from Tombullen, Hay and Maude weirs to piggyback on peak flows in system. This effectively put a peak in the river with the aim to stimulate fish movement and create a temporary floodplain-river interaction. With pre-requisite planning measures in place Commonwealth environmental water was protected all the way to the sea until late April 2023.

Upper Yanco and Colombo Cod Flow, and associated wetlands

On the back of community concern about “very low flows” (as per the Murrumbidgee long term water plan) ~50ML/d at Morundah, water for the environment has been ordered to bolster flows in upper and mid Yanco, Colombo and associated wetlands. Flows commenced 4th May of ~300ML/d via the Coleambally Catchment Drain, and 400ML – 1000ML/d diversions via the Yanco offtake. This flow will continue until mid-June 2023.

Western Lakes complex

Up to ~13GL* of water for the environment is being diverted from the river at Redbank weir to top-up Paika Lake, Cherax, Penarie Creek and Narwie West wetlands in the Western Lakes section adjacent to Yanga National Park. Water is being delivered to maintain habitat for threatened Australasian bitterns, southern bell frogs populations, and re-introduced southern pygmy perch.

The landholder at Narwie noted a good plant response and observed a juvenile sea eagle. The landholder at Paika counted 214 threatened Freckled duck at Paika Lake and theorised they could be breeding. Monitoring staff from Charles Sturt University detected southern bell frogs at every site.

Watering will continue until mid-June 2023.

*Preliminary WaterNSW use estimates only

What has environmental water achieved in the Murrumbidgee?

Scientific monitoring shows environmental water delivered to the Murrumbidgee is providing food, habitat and breeding opportunities for many of the region’s native fish, frogs, waterbirds, plants and other wildlife.

A summary of preliminary results for 2021-22 are below with full monitoring reports available each year.

2021-22

Tuckerbil Swamp. Photo: Michele Groat, CEWO

Repeated high unregulated flows met many of the environmental demands in the Murrumbidgee River catchment in 2021-22. Despite this, it was the biggest water for the environment use year in the Murrumbidgee with over 588 GL delivered. Commonwealth water for the environment was delivered to complement and build on unregulated flows with objectives to enhance habitats and threatened species populations, build ecological resilience and capacity for recovery.

Delivery of Commonwealth and NSW water for the environment successfully:

supported breeding of an estimated 20,000 straw-necked ibis nesting pairs and smaller numbers of many other species, at Bala (Eulimbah Swamp) in Gayini Nimmie-Caira for the second consecutive year.
supported approximately 11,200 pelican nests at Kieeta Lake in Gayini Nimmie-Caira
supported at least 29 active colonial waterbird breeding sites across the Mid-bidgee, Yanco Creek system, Lowbidgee wetlands and including the Junction wetlands; with breeding of numerous species including threatened Australasian and Little bitterns, egrets, spoonbills, herons, cormorants, darters, little grebes, Pacific black and musk ducks, and Eurasian coots
an estimated 45,000 – 50,000 waterbird nests were active in the Murrumbidgee Selected Area in 2021–22. This is comparable to the number of waterbird nests recorded in the last major natural flood event in 2016–17
supported 6 species of frogs (Barking and Spotted marsh frogs, Peron’s tree frog, Plains froglet, Inland banjo frog and the threatened Southern bell frog)
the detection of the threatened Southern bell frog at Western Lakes for the first time as well as supporting distribution of this species in the Coleambally Irrigation Area in all but one of the wetlands that received environmental water.
supported movement of native fish between the Murrumbidgee and Murray rivers, and between the Murrumbidgee River and floodplain creeks and lakes in Yanga National Park by expanding on unregulated flows in the mid-Murrumbidgee and the lower Murrumbidgee River (these flows also provided opportunity for critical exchange of carbon and nutrients)
contributed flows to mitigate low dissolved oxygen in the lower Murrumbidgee River and Yanco Creek system to protect aquatic animals, including native fish
supported populations of a range of native fish, including Carp gudgeon, Australian smelt, Flathead gudgeon, Bony bream, Murray–Darling rainbow fish, unspecked hardyhead, Murray cod, Golden perch and Freshwater catfish
maintained suitable habitat for waterbirds, native fish and frogs in the Western Lakes, Wanganella Swamp and Rhyola Wetland
provided habitat and recruitment opportunities for water dependent animals, including waterbirds in important MIA wetland (Nericon Swamp)
supported all 3 Murrumbidgee turtle species (Broad shelled, Eastern long-necked and Macquarie River turtles) found in the catchment.
extended the duration and managed the recession of three unregulated flow events to maximise mid-Murrumbidgee wetlands and river connectivity. These flows also:
- supported movement of native fish between the Murrumbidgee and Murray rivers, and between the Murrumbidgee River and floodplain creeks and lakes in Yanga National Park
- through Prerequisite Policy Measures, met objectives in the River Murray, and the Coorong and Lower Lakes for native fish and salinity mitigation.

Details of previous Commonwealth environmental use in the Murrumbidgee River Valley are available at: History - Murrumbidgee.

Our partners

Sunshower Lagoon after receiving environmental water in 2019-20. Photo: Vince Bucello

Commonwealth environmental water use is planned, delivered and managed in partnership with a number of individuals and organisations in the Murrumbidgee River region including: