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Australian river catchments and the Great Artesian Basin

Sydney harbour from 16,000 feet, 1966 by David Moore (1927–2003)

Rivers are usually described in terms of their catchment areas. This means that the entire river system - from its source, all its tributaries and down to its mouth are included in any discussion or assessment. Australia has twelve catchment divisions.

The biggest of these is the Murray–Darling, beginning in Queensland flowing through New South Wales and Victoria to its mouth in South Australia. The Murray–Darling River is the third longest navigable river in the world, after the Amazon and Nile.

On the east coast and in the Murray-Darling Basin many Australian rivers have had their flows changed or regulated by human engineering. The Snowy River has been dammed to provide hydro-electric power and been diverted to irrigate land along the Murray River.

In comparison, there are wild rivers in other catchments which are free flowing rivers. Wild rivers exist in the Gulf of Carpentaria, the Timor Sea catchment which contains the Victoria River mouth and the Fitzroy River and there is the Franklin and Gordon in Tasmania - all heritage listed with sites of international significance.

In Australia, there are unique dry inland rivers, such as the Diamantina, part of the Lake Eyre catchment. These river catchments are some of the last of the world's unregulated or free flowing dry river systems, which on occasions flow into Lake Eyre in northern South Australia. In the North-western Plateau, the Gascoyne River is a unique example of a dry river yet with an underground flow of water.

In other catchment divisions the South-West Division contains the Swan River around which the City of Perth is built, the rivers that flow as part of the South Australian Gulf include the Torrens River, part of Adelaide and the South-east Coast division incorporates the Parramatta river, with Sydney Harbour as its mouth.

Australia's drainage divisions or catchments, Bureau of Meteorology

A dry continent – reasonable water but with small run-off into rivers

Whilst Australia might be described as the driest continent, it does not follow that the country is short of water. For the amount of people that live here, Australia is relatively well endowed with water. If there are problems with water, they lie in the location of the water in relation to the large population centres, the amount of water that is lost in the ‘run-off' and the uses to which the water is put.

Rivers form when rain or melting snow runs down the side of a mountain to form streams. Eventually, streams catch more water or join other streams to form a river. Smaller streams that flow into rivers are called tributaries.

It can take millions of years for rivers to form. Rivers carve a path through the land as they pass from their headwaters (the place where a river starts) in the mountains to their mouth (the place where a river empties into the ocean).

In proportion to its area, Australia has the lowest precipitation and run-off of all continents. Most of the rainwater, an average of 85 per cent across Australia, evaporates, or is used directly by trees and plants, or ends up in lakes, wetlands or the ocean. Less than one-fifth of the rain that falls in Australia ends up in its rivers. Because of this, Australian rivers have very irregular flow patterns. This means that sometimes a river is wide, deep and fast flowing, and sometimes it is shallow, narrow and slow flowing.

Most of and the best run-off of water into rivers occurs in only one-quarter of the continent, in northern Australia and Tasmania, and then in the Murray–Darling. Because of the higher mountains in their catchments, with more rain and snow, the Murray and Murrumbidgee rivers have always gathered more run-off than other rivers in the southern landscape.

White-necked Heron and Intermediate Egrets fishing on Coopers Creek. Photo by Glenn Walker

Most of Australia's best run-off occurs in the Gulf of Carpentaria catchment but this is not where there are large populations.

A lot of rain falls on northern Australia, but its arrival is restricted in time and uneven in its distribution. Where and when it occurs is generally impractical for water resource development and there are large variations in how much comes year to year. There is little or no rain for three to six months every year and … The landscape is generally not amenable to storing water and the climate is not conducive to keeping it.
CSIRO, Land and Water, Northern Australia Land and Water Science Review full report, October 2009

If there are problems with Australia's rivers then, this can be analysed as a problem with how Australia has managed its water resources.

Many different animals or fauna live in and around Australian rivers. Fish, frogs, crayfish, mussels, platypuses, swans, ducks, pelicans, kangaroos, lizards, snakes, crocodiles, turtles and tortoises can all be found living in river or riparian environments. The river, its groundwater system and its associated plants and animals create a riverine ecosystem.

Where water is permanent, large changes in flow regime can significantly alter ecosystems. The flow of a river, along with salinity in rivers has affected the plants and wildlife associated with Australian rivers.

The Great Artesian Basin

Spring wetland in Central Queensland, part of the Great Artesian basin. Courtesy of Queensland Herbarium

Groundwater systems, the water beneath the surface, are part of a river's catchment and are sometimes simply known as basins.

The largest groundwater basin, the Great Artesian Basin (GAB), lies under parts of four catchment divisions: the Lake Eyre, Murray-Darling, North-east Coast and Gulf of Carpentaria. It is the largest and deepest artesian basin in the world. The GAB provides the only reliable source of fresh water throughout much of inland Australia.

Waters of the Great Artesian Basin feed springs and wetlands, although some of these exist in dry lands. The springs supported rich marine life including molluscs as well as Aboriginal communities and their trade routes. The springs of the GAB also supported the development of European trade routes with the building of the Overland Telegraph Line.

Artesian bore Balcaldin, Queensland (detail) c 1907, Mobsby Coll, Fryer Lib, Brisbane.

The discovery of bore water was first realised in 1878 near Bourke, NSW, in 1886 near Barcaldine and in 1887 near Cunnamulla, Queensland.

By drilling water wells, bore water from the Great Artesian Basin became an important water supply for Europeans. Bore water played a significant role in developing the cattle industry and supporting the settlement of European populations in inland Queensland and north and west of the Darling River in New South Wales.

However, since European settlement, a massive quantity of Great Artesian Basin groundwater has been lost to evaporation as it flows down open drains and pipes fed by bores. Many bores initially flowed at rates of over 10 megalitres per day (ML/d). Total flow from the Basin reached a peak of over 2 000 ML/d around 1915, from approximately 1,500 bores. In 2000, the majority of flows were between 0.01 and 6 ML/d. The loss of water from bores has had a dramatic effect on aquifer pressure and hence spring-flows and the health of river catchments.

The management of the GAB and related activities across communities in Queensland, NSW, South Australian and the Northern Territory is coordinated by the Great Artesian Basin Coordinating Committee (GABCC). Advice is provided to all governments as well as the Australian Government about the most efficient, effective and sustainable methods of resource management.

A man bathing in the water flow from the bore head at Noorama No. 1 Bore. Depth 1,502 ft. Yield per 24 hours 2,304,000 gallons. Temperature 110 degrees Fah, Cunnamulla, Queensland, 1894. Queensland Pictures.

Historical sources, including the diaries of surveyors in Queensland during the 1800s, allow us to compare the health of the spring water. In 1939 the water wastage from the free-flowing bores was recognised as a major problem. A report was commissioned to investigate the nature and structure of the Basin. Following the report's publication in 1954, each state and territory managed the GAB separately.

In 2001, the Artesian Springs Ecological Community was seen as endangered. Major threats to Artesian Springs were trampling and grazing by stock and feral animals as well as alteration of flow or unsustainable extraction of water from artesian bores reducing flows to the mound springs. The drying up of the mound springs due to a drop in water pressure has probably resulted in extinction of several invertebrate species.

In New South Wales, the introduction of exotic grasses has dominated the habitat of spring wetlands and contributed to their decline. However, in South Australia, the condition of most of the springs is close to their natural state.

Protecting the natural values of the springs and ensuring the supply of fresh spring water relies upon a bore capping program. This should provide a partial restoration of artesian pressure and enhance spring flows.

Artesian Basin recovery, Nala bore, courtesy of NSW Water

In 2006, only 44 per cent of the original 171 spring complexes had at least some springs that were still active. Of these active springs, about 20 per cent have suffered major or total damage as a result of excavation of the wetlands. A 2010 National Recovery Plan set out to control the flows from strategic bores with reference to reviewing historic spring flows.

In New South Wales, the Office of Water is recovering water in the NSW Great Artesian Basin by capping and piping free-flowing artesian bores.The Cap and Pipe the Bores program gives landholders in the Great Artesian Basin financial incentives to cap and pipe their bores.

It was estimated that in NSW, in the past, up to 95 per cent of artesian water was being wasted through evaporation and seepage. Today, the Cap and Pipe the Bores program is improving water supply by saving 47,000 ML of water a year, reducing salt discharge by 40,000 tonnes a year and assisting land managers to achieve more sustainable property and stock management. It is formally known as the Water Sharing Plan for the NSW Great Artesian Basin Groundwater Sources.

Perennial and non-perennial rivers and water bodies, map, Bureau of Meteorology

Permanently and seasonally flowing rivers

A key feature to understand about the river catchment and drainage divisions is whether rivers are perennial (permanently flowing) or non-perennial (seasonally flowing), and how wetlands are connected to the rivers. Unlike many other parts of the world, most of Australia's rivers, streams and lakes do not always have flowing water in them, even in the tropics. Yet even non-perennial sources of water have been important historical sources of water for people and industry.

Water use and water management

The calculation of how much water Australians have to use is based on the run-off. This is measured in megalitres or giga litres (GL). Water authorities approve the use of this water, and the quantities that can be extracted from rivers and other storage facilities. Uses for this water includes: agriculture, forestry, fishing, mining and manufacturing. Other uses are for generation of hydro-electricity, especially in Tasmania, and recreation use.

In some parts of Australia, the commitment for the use of water has been higher than its practical limits, especially in the Murray–Darling, the South Australian Gulf Drainage Division as well as in some smaller systems. This problem usually occurs where water is used for irrigation in areas such as the Namoi Valley, Condamine Vallery and North Adelaide Plains.

Libby Price, on the Murray at Colignan, south of Mildura, 2007, courtesy of ABC

When drought occurs in the irrigated areas of the Murray Darling Basin, as it did in 2007, farmers in New South Wales and Victoria received no water allocation at the start of the irrigation year. In South Australia, they were promised only 4 per cent of their normal allocation.

Catchment management

Since 2000, there have been many changes to catchment management bodies in Australia. These changes have included changes in their powers, responsibilities, names, reporting channels, and the names and structures of government agencies with which they must work.

In NSW in 2003, 13 Catchment Management Authorities (CMAs) were created and became statutory authorities. They have the same name in Victoria but are Catchment Councils in Western Australia and Natural Resource Management Boards in South Australia.

In the eastern states, CMAs deliver programs and outcomes on the ground either in their own right or in partnership with other organisations including councils and landcare groups. Catchment Management Plans for Australia's rivers were developed by the CMAs. An example is the Southern Rivers CMA which has planning responsibility for both water resources and conservation for the Southern Rivers in NSW.

Tina Clemens, Hunter-Central Rivers CMA 's Riparian-Vegetation officers gathering data. Courtesy of Hunter-Central Rivers CMA.

The Hunter-Central Rivers CMA engages in mapping, monitoring, assessing biodiversity, birds, marine life, shore lines and estuarine habitats. Education resources about floods and flood patterns, managing riparian or river lands, and related vegetation on private lands have been prepared to help people living in the catchment and with the Hunter River.

National framework for river catchments: 2007, 2010–

In 2007, the Australian Government commissioned the Commonwealth Scientific and Industrial Research Organisation (CSIRO) to estimate and assess water yield and use. The purpose was to provide the science for sustainable planning and management of water resources.

The first project was in the Murray–Darling Basin. In 2010, the Australian and state governments, agreed to asses three other areas: northern Australia, Tasmania and south-west Western Australia, with the South West Catchments Council.

Catchments, like those managed by the Southern Rivers Catchment Management Authority, show incredible biodiversity in their ecosystems and landscapes. The catchments, by definition, necessarily move from the escarpment through a hinterland to a coastal environment. The vegetation moves through heath lands, rainforest, dry sclerophyll forest and woodlands with diverse plants and animals. The more diversity of plants there are, the better it is for animals: birds, mammals, reptiles, amphibians, insects and humans. A healthy ecosystem contributes to soil and air quality.

Lake Clifton Thrombolites by Kim Wilson, courtesy of South-west Catchments Council

However, the vegetation areas in the catchment are fragmented and not connected. Some of the vegetation types are rare. Regeneration of vegetation, by fencing bush areas off from cattle, weeding and seeding, aims to provide link corridors. This in turn provides a network of corridors through the escarpment and catchment. This can establish healthy ecosystems that add viability and productivity to working properties.

Today CMAs, and other invested authorities, take into account the unique values of Australian rivers and plan for the protection and management of their ecosystems. Catchment planning aims to optimise economic, social and environmental outcomes.

Healthy rivers support agricultural, industrial and ecological systems, as well as being important recreational places. At the same time it is recognised that any water resource management has to prioritise the sustainability of the river environment – the river of life.

Useful links

Look, listen and play

Educational Kits

Teacher guide and lesson plans – Lower secondary

Great Artesian Basin

Catchment management

Understanding rivers

Rivers as habitats

Environment issues and assessments – ebbs and flows

Last updated: 24 March 2016
Creators: Kathryn Wells

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