Murray River ecosystem

• Category: Inland Aquatic Biomes.
• Geographic Location: Australia.
• Summary: The Murray River supports many rich habitats in a variety of climate and elevation zones, but is under great stress from human activity.

The Murray River is one of the largest rivers in the Murray-Darling Basin and among the longest in Australia, at 1,565 miles (2,520 kilometers). The climate and habitats along the Murray River change considerably, beginning as subtropical in the far north; changing to cool and humid in the eastern uplands, Snowy Mountains, and temperate southeast; and ending as semiarid to arid in the western plains. The Murray begins in the Australian Alps, drains the western side of the range, then meanders northwest over the inland plains as the border between Victoria and New South Wales, finally turning south for 310 miles (500 kilometers) to Lake Alexandrina before passing through the Murray Mouth to reach the Southern ocean.

The Murray-Darling river system drains inland Victoria, New South Wales, and southern Queensland. The system as a whole extends 2,330 miles (3,750 kilometers). The prehistoric Lake Bungunia formerly was the terminus of the Murray River; at maximum, it stretched over 13,000 square miles (33,000 square kilometers). But the lake long ago drained, as the wet period of the Murray-Darling Basin ended a half-million years ago. Since then, the region has been mostly arid, and species long ago common to the Murray are now restricted to Queensland.

The Murray’s volume of water is minuscule compared to other rivers of its length in the world. Before the regulation works on the river, extreme drought would sometimes reduce some portions of the river drastically and stop the flow in a few other areas. The river system obtains 58 percent of its natural flow; the region is Australia’s breadbasket and the river is heavily drawn upon. Irrigation using the Murray’s waters began in the 1850s, with the first large pumping station built in 1887, allowing farming along the river to rapidly expand. In the twentieth century, the river was the site of four reservoirs, as well as locks and weirs for a proposed but obsolete system for river traffic. In the twenty-first century, about 40 percent of the water was diverted from the river basin.

Biodiversity

Notable flora in the Murray River basin encompasses one of the world’s largest river red gum forests, a flood-fed, wetland-type ecosystem. One 70-mile (112-kilometer) segment of the river features the Barmah Forest, a Ramsar-recognized Wetland of International Importance, along one bank, and the adjoining New South Wales Murray Valley National Park and Murray Valley Regional Park (previously known as Millewa Forest) on the other. The Barmah-Millewa Forest form the world’s largest river red gum forest. Forests of red gum appear both upland and right along the river fringe. These river red gum forests are a product of the Cadell Fault, which altered the route of the Murray 25,000 years ago.

These river red gum forest floodplains are vital because of their ability to support a broad range of threatened and vulnerable species of every type. Observers here have documented the Barmah-Millewa’s value to such species as the flowering slender darling pea, Mueller daisy, and Moira grass among flora; the trout cod, silver perch, southern bell frog, giant banjo frog, inland carpet python, broad-shelled turtle, and squirrel glider among terrestrial and aquatic fauna; and the intermediate egret, plumed egret, blue-billed duck, superb parrot, and white-bellied sea-eagle among avians.

The Murray River basin as a whole is home to identified endangered fauna including at least 35 bird species, 16 mammal species, and 69 native fish species. With some 30,000 wetlands, about 7 percent of the Murray River basin has been set aside in reserves particularly to support migratory birds. The site is bioregionally significant for moira grass (Pseudoraphis spinescens), supporting the largest expanses of this species in the Murray–Darling Basin.

Fish species that are relatively widespread here include the Murray cod, trout cod, golden perch, silver perch, Australian smelt, and the eel-tailed catfish. The Murray short-necked turtle and Murray River crayfish are among the species that are strongly associated with the river, but it also has species that appear elsewhere in the southeast, including long-necked turtles, and varieties of shrimp, rat, and platypus.

Threats

River regulation since Europeans settled the area has adversely affected native fish and aquatic life, causing some species to decline until they become endangered or rare. The Murray’s natural flow changed, benefiting agriculture but disrupting ecosystems inside and outside the river. Agricultural runoff and pest species have also damaged the river, and increased salinity of both the water and the land, potentially making it unusable in the medium to long term. The major flood of the Murray in 1956 left river towns under water for longer than six months. However, because of heavy rains and storms caused by climate change, the Murray River has flooded more often. It has flooded in 2016 and again in 2022 and 2023, with the latter flooding reported as the third highest on record.

Weirs and dams negatively impact the river biome. They prevent migrations of fish and have in many cases displaced the river-adapted Murray crayfish with a floodplain species, the yabbie. Dams and weirs alter seasonal flood cycles, disrupting recruitment and spawning. Since late 1940s, the Murray cod and river blackfish have declined as water control systems have proliferated. Human-built fishways along the Murray, in some cases, are poorly designed and tend to inhibit the seasonal movement of such species as golden perch, Australian bass, and barramundi.

Water removal from the Murray River takes up to more than 40 percent of the available flows, resulting in insufficient water for habitats at most segments, including its estuary and the floodplain forests. The Murray system includes several lakes whose salinity now varies, although by the twentieth century they were commonly fresh. This may be the result of human-created changes in the environment. Droughts in 2000–07 stressed the red gum forests, raising concern about their survival. Increased droughts in Australia, thought to be the result of climate change, are likely to continue to stress the red gum forests. Reduced rainfall and increased evaporation as a result of higher temperatures caused by climate change are also likely to place undue stress on the environment. The Murray–Darling Basin Plan was enacted in 2012 under the Commonwealth Water Act 2007. It established limits on the amount of water that can be extracted from this important river system, protecting the region and biodiversity.

Bibliography

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Crawford, Jack. “How Capitalism Is Killing the Murray-Darling River Basin.” Redflag, 19 July 2021, redflag.org.au/article/how-capitalism-killing-murray-darling-basin. Accessed 12 Mar. 2026.

Mallen-Cooper, Martin. Fishways and Freshwater Fish Migration on South-Eastern Australia. University of Technology Sydney, 1996.

“National Water Account 2023: Murray–Darling Basin: Region Description.” Australian Government Department of Meteorology, www.bom.gov.au/water/nwa/2023/mdb/regiondescription/geographicinformation.shtml. Accessed 12 Mar. 2026.

“Native Fish Status Assessment 2023.” Native Fish Recovery Strategy, Mar. 2025, www.mdba.gov.au/sites/default/files/publications/native-fish-status-assessment-2023-summary.pdf. Accessed 12 Mar. 2026.

Pittock, Jamie. “Challenges of Freshwater Protected Areas.” World Wildlife Fund for Nature, Oct. 2005, www.panda.org/es/?17772/Challenges-of-freshwater-protected-areas. Accessed 12 Mar. 2026.

Roberts, Nick, et al. 13 Thirsty Species. Victorian National Parks Association and Environment Victoria, 2010.

Weir, Jessica K. Murray River Country: An Ecological Dialogue With Traditional Owners. Australian Institute of Aboriginal and Torres Studies Press, 2009.

“What Is the Murray–Darling Basin Plan?” Victoria State Government: Department of Energy, Environment and Climate Action, 8 Sept. 2023, www.water.vic.gov.au/our-programs/murray-darling-basin/what-is-the-murray-darling-basin-plan. Accessed 12 Mar. 2026.

Willis, Belinda. “Flooding Plains as River Murray Hits Six-Year Flow Peak.” In Daily, 22 Aug. 2022, indaily.com.au/news/2022/08/22/flooding-plains-as-river-murray-hits-six-year-flow-peak/. Accessed 12 Mar. 2026.