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Australia
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Australia is the driest continent after Antarctica. While the surface flow per capita is higher than in many nations, such flows are extremely variable both in seasonal terms and in year-to-year variations about the mean annual or monthly flow. Furthermore, much of the total flow is in the tropical north where human populations are low, or in short, fast-flowing coastal rivers. The only river system of note, the Murray-Darling, is puny compared to the world's great rivers. Its variability is epitomized by the troubles encountered by river-boat captains on the Darling in the late nineteenth century; they could be stranded for months on a dry river bed, or find themselves tens of kilometers from the main channel when it became undistinguishable during floods. After drought, storm-fed flows are predicted weeks or even months ahead and anticipated with a mixture of relief and foreboding, depending on how much water is likely to come.
Many Australian ecosystems and individual plant and animal species are well adapted to variations in moisture availability. Many ecosystems can be accurately described as "stop-go", going into a form of suspended animation under drought conditions and exploding into life when rain falls or floodwaters arrive. One likely conflict in water management is between the human desire for a steady, reliable, year-in, year-out supply of water and the dependence of ecosystems and species on variability.
Unfortunately, many of the scarce surface water bodies - rivers, lakes, reservoirs and estuaries - are being polluted by human activities, making them less useful for both people and other species. Many of Australia's rivers, both near large cities (for example, the Nepean-Hawkesbury river of outer western Sydney) and in agricultural areas have suffered. The Darling River has had blue-green algal blooms as a result of low flows combined with agricultural and town-sewage pollution. Many inland rivers have become more saline due to a combination of low-flow periods and saline water from irrigation areas seeping back into the river, as in the case of the Murray.
Murray-Darling Basin
The Murray-Darling Basin is the catchment for the Murray and Darling Rivers and their many tributaries. Extending from north of Roma in Queensland to Goolwa in South Australia and including three quarters of New South Wales and half of Victoria it is theheartland and the economic powerhouse of rural Australia. It extends across one-seventh of the continent and has a population of nearly two million people. Another million people outside the region depend heavily upon its resources.
The Murray-Darling Basin generates about 40 percent of the national income derived from agriculture and grazing. It supports one quarter of the nation's cattle herd, half of the sheep flock, half of the cropland and almost three-quarters of its irrigated land. The Basin contains more than twenty major rivers as well as important groundwater systems. It is also an important source of fresh water for domestic consumption, agricultural production and industry.
The riverine environments of the Murray-Darling Basin support a wide range of animal and plant communities. This is particularly evident in the large number of wetlands throughout the Basin. There are over 30 000 wetlands in the Murray-Darling Basin. Ten of these wetlands are of international significance and listedas Ramsar Wetlands. These include Chowilla, Barmah-Millewa Forests, the Coorong, Gunbower Forest, Hattah-Kulkyne Lakes, the Kerang Wetlands, Lake Albacutya and the Macquarie Marshes. The Basin's wetlands are among its most productive and biologically diverse ecosystems, providing the essential breeding and feeding habitats for many species of waterbirds, fish, invertebrates and plants.
As a large, very shallow drainage basin covering more than one million square kilometres with only one exit flowing out of Lake Alexandrina in South Australia, the Murray-Darling Basin is an unusually complex biophysical system. Changing patterns of land use have groundwater impacts which are felt hundreds and even thousands of kilometres downstream.
The developmentthat made the economic productivity of the Basin possible has also caused many biophysical changes. Some of these changes have reduced biodiversity and threaten the potential of economic production in the future. In the south many rivers now have low flows in winter and spring when rain in their catchments is being captured in the storages. In the summer and autumn when flows were traditionally low, they run full to supply the irrigation regions.
The operation of the storages and the extraction of large volumes of water for consumption off-stream have also reduced the annual and seasonal variability which shaped the ecology of the region.
Beyond the riverine corridors extensive clearing of native vegetation has dramatically increased the volumes of rainwater leaking through the soil profile to groundwater systems. Groundwater levels are now rising in many parts of the Basin causing widespread and serious salinity problems. Broad-scale clearing has also reduced the habitat for many native plant and animal species.
Management of the Murray-Darling Basin requires the balancing of many values and assets that are potentially in competition. Tensions exist between some production-orientated activities and environmental needs. There is also competition between different economic interests. To help resolve these issues a framework for political and administrative cooperation has been created, initially with a focus just on the water resources of the River Murray and lower Darling.
The Lake Eyre Basin
The Lake Eyre Basin is the world's largest internal drainage system. It covers approximately 1.2 million square kilometres of arid and semi arid Central Australia. This is about one-sixth of the continent or the same size as the Murray Darling system or about twice the size of the US state of Texas.
It is considered to be one of the world's last unregulated, wild river systems. Unlike other river systems, flows in the Basin are highly variable and unpredictable.
Lake Eyre itself, at 15 metres below sea level, is Australias lowest point. It is also the fifth largest (9,690 square kilometres) terminal lake in the world although it usually contains little or no water.
All the rivers and creeks are ephemeral with short periods of flow following rainand extended periods of no flow. The volume of flow decreases downstream reflecting increasing aridity towards Lake Eyre and the huge dispersal system of braided channels, floodplains, waterholes and wetlands on the way. The many large permanent waterholes in the system provide vital habitat for wildlife and are important to towns, communities and pastoral holdings.
The Basin is part of Australia's arid zone and the ecosystems it supports are varied and often unique. Land use within the Basin is equally varied, and includes (but is not limited to) pastoralism, mining, tourism, oil and gas exploration and production, conservation and Aboriginal activities. The area is culturally significant and contains a wealth of Aboriginal and non-Aboriginal history.
The Lake Eyre Basin is rich in environmental, economic and cultural assets that are important for people both within and outside the Basin. The sustainable management of these assets is in the local, regional and national interest.
To read more about river basin issues in Australia go to The Murray-Darling Basin Commission or
Lake Eyre Basin Coordinating Group
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