Murrumbidgee River
The Murrumbidgee River, located in southeastern Australia, is the second-largest river in the Murray-Darling Basin and spans approximately 1,050 miles (1,690 kilometers). Its source is in the alpine Kosciuszko National Park, flowing through diverse landscapes such as the Monaro High Plains and the Australian Capital Territory before joining the Murray River. The Murrumbidgee supports a rich variety of ecosystems, including significant wetlands like Fivebough Swamp and the Lowbidgee Floodplain, which are home to numerous endemic and endangered species, such as the plains-wanderer and glossy black cockatoo.
However, the river faces serious ecological challenges, primarily due to extensive irrigation practices and river regulation that began in the late 19th century. These interventions have led to a decline in the river's health, increased salinity, and significant loss of biodiversity. Climate change further exacerbates these issues, contributing to decreased rainfall and lowered water levels since 1990, which poses risks to both the environment and local communities. As the Murrumbidgee continues to experience these challenges, concerns grow over the sustainability of its ecosystems and the livelihoods dependent on its water.
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Murrumbidgee River
- Category: Inland Aquatic Biomes.
- Geographic Location: Australia.
- Summary: The Murrumbidgee is the second-largest river in the Murray-Darling Basin, but lower water levels due to river regulation and irrigation have resulted in a decline in the health of the river, a loss of biodiversity, and an increase in salinity.
The Murrumbidgee River has its source in Kosciuszko National Park in the state of New South Wales, Australia. From this alpine region, it runs southeast, winding through the Monaro High Plains before flowing north through the Australian Capital Territory. Then it heads west down the South West Slopes and across low-lying plains to flow into the Murray River, which meets the sea at Encounter Bay, South Australia.
Covering a distance of 1,050 miles (1,690 kilometers) from its source near Kiandra in New South Wales to its confluence with the Murray River, the Murrumbidgee is the third-longest river in the expansive Murray-Darling drainage system. This system covers a land area in excess of 386,102 square miles (1 million square kilometers), collecting the water draining west of the Great Dividing Range.
The Murrumbidgee is fed by several tributaries: the Cotter, Tumut, Molonglo, Yass, and Lachlan rivers. The catchment has one of the most diverse climates in New South Wales, ranging from the alpine areas of Kosciuszko National Park and the Monaro plains, to the rich grazing and grain belts of the South West Slopes and plains, and to the shrublands and grasslands of the semiarid western Riverina.
Biodiversity
Within the Murrumbidgee catchment are a number of wetlands. Those of international ecological significance include Fivebough Swamp, Tuckerbil Swamp, and the Lowbidgee Floodplain. These wetlands support a diversity of plant, bird, fish, and animal life, some of which are considered to be “icons” because of their profile or endemic (found nowhere else on Earth) nature. Many are now endangered. High-profile species include the plains-wanderer, superb parrot, southern bell frog, trout bluenose cod, and the grey-crowned babbler. The glossy black cockatoo that once thrived in the lush Murrumbidgee wetlands is now considered endangered. Endangered species with a population entirely within the Murrumbidgee Catchment include the white-browed treecreeper and squirrel glider. Other endemic fauna include the southern corroboree frog and northern corroboree frog.
Endemic plant species found in the biome include the bethungra spider orchid, burrinjuck spider orchid, Mueller’s eyebright, bredbo gentian, wee jasper grevillea, tumut grevillea, lemon zieira, yaas daisy, slender darling pea, and kiandra leek orchid. Many of these species are considered threatened and of high conservation value.
Threats
Settlement of land along the Murrumbidgee took place largely from the 1830s. It is an area that has been transformed by irrigation. Initial investigations into irrigation were made in the 1890s, partly in response to drier years, but also in an attempt to more closely settle the land. For sheep and cattle grazing to give way to farming, a more reliable source of water was needed rather than the periodic inundations in wet years.
The development of a virtual monoculture of rice in areas such as the Coleambally highlights the problems that have developed from the addition of large quantities of water to the land. The Coleambally Irrigation Area was the last major component that used water diverted via the Snowy Mountains Scheme. A rise in the water tables here became evident after 10 years. Before irrigation, the water table was about 66 feet (20 meters) below the surface, but by 1983, it was estimated to be rising by 5.2 feet (1.6 meters) a year. By 1985, shallow water tables within 7 feet (2 meters) of the surface were a problem in at least two districts, resulting in waterlogging and salt deposits.
The flow of the Murrumbidgee and many of its tributaries is now highly regulated, and they are thus lined with stressed habitats. In the 1960s, another major storage, the Blowering Dam, was constructed in the headwaters of the Murrumbidgee, on the Tumut River, to regulate the water made available from the Snowy Mountains Scheme. The Tantangara Reservoir was constructed from 1958 to 1960. Conservatively, this reservoir reduced by 50 percent the annual flow of the Murrumbidgee. The consequent damage to the river system became a cause for concern in the mid-1960s, when years of drought further reduced river flows.
Salinization has become one of the most serious problems in the Murray-Darling. Before river regulation, the periodic floods due to the cycles of El Niño Southern Oscillation flushed the river system. The reduced flow in the Murrumbidgee in particular has been a major contributor to increased salinization in the basin. Before extensive irrigation, the natural flows of the Murrumbidgee and its tributaries provided water to dilute the salinity of the lower reaches of the Murray River. By the mid-1970s, virtually all of the water in the Murrumbidgee had been allocated to irrigation. Climate change has significantly decreased the amount of rainfall the river receives. This has led the water level in the river to significantly drop from 1990 to 2024. Experts predict a greater drying of the wetlands and surrounding areas. This lack of water greatly affects the people living in the region. With the river having lost more than half its water scientists warn that ecosystems are beginning to collapse.
Bibliography
Phillips, Peter J. River Boat Days: On the Murray, Darling, Murrumbidgee. Melbourne, Australia: Landsdowne, 1974.
Spear, Milton. "The Murrumbidgee River's Wet Season Height Has Dropped by 30 Percent Since the 1990s, and the Outlook Is Bleak." The Conversation, 11 Aug. 2021, phys.org/news/2021-08-murrumbidgee-river-season-height-1990s.html. Accessed 20 Nov. 2024.
Wassens, Skye, et al. "Commonwealth Environmental Water Office Monitoring, Evaluation and Research Program: Murrumbidgee River System Technical Report, 2014-2022." Charles Sturt University, 2023, researchoutput.csu.edu.au/en/publications/commonwealth-environmental-water-office-monitoring-evaluation-and-9. Accessed 20 Nov. 2024.
White, Mary E. Listen ... Our Land is Crying. Australia’s Environment: Problems and Solutions. Kenthurst, Australia: Kangaroo Press, 1997.
Young, W. J. Rivers as Ecological Systems: The Murray Darling Basin. Canberra, Australia: Murray Darling Basin Commission, 2001.