National Water Account 2019

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Key findings

Climate and water

Water Accounting Statements

Supporting information

Region description

Reference information

Focus area

Border Rivers

Murray–Darling Basin: Geographic information

General description

Area: 1,055,600 km²
Population: 2,252,000 (Australian Bureau of Statistics [ABS] 2016a)

Figure R1 Contextual map of the Murray–Darling Basin region

• The Murray–Darling Basin region is defined by the catchment areas of the Murray and Darling rivers and their many tributaries. It contains 40,000 km of major rivers and approximately 440,000 km of rivers in total.
• The region makes up 14% of mainland Australia and covers 75% of New South Wales, more than 50% of Victoria, sections of Queensland and South Australia, and all of the Australian Capital Territory
• The majority of the Murray–Darling Basin region is made up of extensive plains and low undulating areas; the highland areas of the Great Dividing Range are located along the eastern and southern boundary of the region.
• About 55% of Australia's water use occurs in the region, mostly from surface water for agricultural purposes.

Land use

Figure R2 Land use in the Murray–Darling Basin region

Source: Australian Bureau of Agricultural and Resource Economics and Sciences (2018).

• The Murray–Darling Basin region is one of the more productive agricultural regions in Australia containing 40% of all Australian farms by number (Murray–Darling Basin Authority [MDBA] 2016a).
• 63% of the region is for grazing, which is the dominant land use activity in the region.
• Irrigated agriculture makes up around 3% of the region's total area, but is the major water user in the region.

Figure R3 Irrigated areas within the Murray–Darling Basin region

Sources: Geoscience Australia irrigation gazetted areas and ABARES land use map.

• The Murray–Darling Basin region contains 70% of Australia's irrigated land area (MDBA 2016a). The major irrigation areas in the region include Murrumbidgee Irrigation, Coleambally Irrigation, Murray Irrigation and Goulburn–Murray Water.

Significant aquatic ecosystems

Figure R4 Ramsar wetlands in the Murray–Darling Basin region

• The Murray–Darling Basin region contains over 30,000 wetlands, including 16 Ramsar listed wetlands.
• The region also contains over 100 wetlands of national importance, as listed in the Directory of Important Wetlands in Australia. Many of these sites are significant to Aboriginal and other local communities.
• The iconic River Murray sites are a collection of important locations along the River Murray, selected for their high ecological value and cultural significance. Given the value of these icon sites, The Living Murray program was established to improve the environmental health of the river system.

Significant Indigenous cultural places and practices

• The Murray–Darling river system has been, and continues to be, of high importance to Aboriginal people. Aboriginal people view themselves as an integral part of the land and river systems and feel a strong responsibility for the health of rivers and wetlands.
• Today there are almost 50 Aboriginal nations whose traditional lands are within the Murray–Darling Basin (MDBA 2016a).
• There are at least 10,000 known Aboriginal sites in the Murray–Darling Basin, indicating the deep physical, economic, and spiritual dependence of Aboriginal people on its rivers, creeks, lakes, and wetlands.

Water resources

• The water resources in the Murray–Darling Basin region are highly developed.
• On average, more than 40% of the total surface water runoff in the region is diverted for consumptive or environmental management purposes.
• Approximately 1.8 million ML of the region's groundwater resources are extracted each year from a small number of large aquifers, mainly for agricultural use.
• The Murray–Darling Basin Authority's Basin Plan has now established sustainable diversion limits (SDLs) for both surface water and groundwater use within the Murray–Darling Basin region.

Surface water

Storages

Figure R5 Major storages in the Murray–Darling Basin region; capacity of each storage is also shown

• The northern part of the Murray–Darling Basin region consists mostly of unregulated systems, although major storages are located along some of the rivers including Border, Gwydir, Namoi and Macquarie.
• The southern part of the region is mostly a regulated system with major storages in many of the rivers. The storages in the three major southern rivers—the Murrumbidgee, Murray, and Goulburn—are used to provide regulated flows downstream as far as the lower lakes in South Australia.
• Further information on the water storages in the region, including current levels and volumes, is available from the Bureau of Meteorology's Water storage website.

Rivers

• Many of the rivers and streams in the northern part of the region are ephemeral and flow for a short period following rainfall. Generally, water users in much of this area rely on collecting water during floods and storing it on-farm for later use.
• Most of the rivers in the southern part of the region are regulated; flows in these rivers are influenced by dam operations and diversions for consumptive use.

Figure R6 Key flow gauging station locations along the main rivers within the Murray–Darling Basin region

Figure R7 Mean monthly flows at selected gauging stations in the Murray, Darling and Ovens rivers; mean monthly rainfall for the Murray–Darling Basin region is also shown

• Flow in the River Murray is primarily influenced by the status of regulation.
• Flow in the Darling River reflects the rainfall pattern for the northern part of the region, with higher streamflows in the late summer–early autumn months (February–March) following the higher summer rainfall period and a second peak in the late winter–early spring months (August–October) following the winter rainfall.
• In the Ovens River, a largely unregulated major river within the southern part of the region, the seasonal flow characteristics reflect the local rainfall pattern. Higher rainfall and streamflow usually occurs during the winter–spring months (June–November); less rainfall and streamflow occurs in summer and autumn.
• Further information on other gauging stations across the Murray–Darling Basin region is available from the Bureau of Meteorology's Water Data Online website.

Water transfers

• In a number of locations, water is transferred into or out of the Murray–Darling Basin region, as well as from one catchment to another within the Murray–Darling Basin region.

Figure R8 Water transfers into, out of and between catchments within the Murray–Darling Basin region

• The primary water transfer into the Murray–Darling Basin region is via the Snowy Mountains Hydro-Electric Scheme that transfers water to the Murrumbidgee and Murray rivers.
• Other transfers into the region are from the Glenelg catchment to the Wimmera system and the Cressbrook Reservoir to Toowoomba and surrounds.
• Transfers out of the Murray–Darling Basin region include water from the South Australian River Murray to supply metropolitan Adelaide and country towns; Fish River Water Supply Scheme within the Macquarie River system to the Blue Mountains area in the Sydney region; and the Goulburn River system via the North–South Pipeline for distribution to Melbourne.
• There are also channels and pipelines in rivers within the southern part of the region that allow water to be moved and traded from one catchment to another. For example, the Waranga Western Channel delivers water from the Goulburn River to the Campaspe, Loddon, and Wimmera–Avoca catchments.

Groundwater

• The groundwater systems of the Murray–Darling Basin region can be categorised into four distinct hydrogeological types: the aquifers in sedimentary deposits of the Murray Basin and the Great Artesian Basin (GAB) within the low topographic landscapes; the shallow aquifers of the Darling River Basin overlying the GAB; valley-fill alluvium in the highlands bordering the region; and the local fractured rock aquifers of the Great Dividing Range and other areas.
• The different groundwater systems behave mostly independently of each other, with only relatively small volumes of groundwater directly flowing from one system to another.
• A substantial volume of groundwater enters the rivers in the upper and middle catchments as base flow and then re-enters the groundwater systems further down through seepage from streambeds (Murray–Darling Basin Commission 1998).

Figure R9 Cross-section diagram of groundwater aquifers in the southern part of the Murray–Darling Basin region

• Sedimentary and alluvial aquifers are the most important sources for groundwater supply; more than 95% of the region's extractions are from these aquifers.
• The GAB is the largest groundwater basin in Australia and underlies about one third of the Murray–Darling Basin. The GAB is recharged in small areas of the Murray–Darling Basin (along the southeastern edge of the GAB) where the aquifer layers are exposed at the land surface.
• Fractured rock aquifers occur in the region's highland areas. The volume of groundwater extracted from these aquifers is relatively low due to the difficulty of obtaining high yields from fractured rocks.

Other water resources and systems

Farm dams

• Farm dams (runoff dams) refer to landscape catchment storages used to harvest runoff, floodwater, or collect rainwater. They are an important water resource in the region; however, water held in farm dams is considered to be taken from the shared pool of water resources and, as such, is not included as part of the region's water assets.
• There are over 650,000 farm dams within the region (Srikanthan et al. 2015) holding approximately 2,168,000 ML (Sinclair Knight Merz 2007) or 9% of the total surface water storage capacity in the Murray–Darling Basin region.
• The water held in these farm dams is primarily used for agricultural and for stock and domestic purposes.