Murray–Darling Basin: Geographic information
The Murray–Darling Basin is one of the productive agriculture regions in Australia. It contains 70% of Australia's irrigated land area. The region also contains over 30,000 wetlands including 16 Ramsar-listed wetlands. Surface water is sourced for irrigated agriculture, urban water supply, environmental needs and hydroelectric generation in the region. Groundwater is also an important water source, primarily used for irrigated agriculture.
General description
Area: 1,055,600 km2, which is 14% of mainland Australia
Population: 2,190,000 (Australian Bureau of Statistics [ABS] 2011)
The Murray–Darling Basin region is defined by the catchment areas of the Murray and Darling rivers and their many tributaries. The region covers 75% of New South Wales, more than 50% of Victoria, sections of Queensland and South Australia, and all of the Australian Capital Territory, as shown in figures R1 and R2 below. It contains:
- 40,000 km of major rivers and approximately 440,000 km of rivers in total
- some 30,000 wetlands, covering an area of around 25,000 km²
- about 60,000 km² of floodplain area, which represents approximately 6% of the Murray–Darling Basin region.
Figure R1 The Murray–Darling Basin region within Australia
The Murray–Darling Basin region is a complex, interconnected river system rather than a series of separate catchments; however, its diverse climate and landscape and the presence of artificial structures means not all parts of the system are connected to the same extent. For example, rivers such as the Wimmera will never contribute to downstream flows and the Paroo and the Lachlan only rarely.
The Murray–Darling Basin region presents a varied landscape, from semi-arid ephemeral river systems in the north to highly regulated river systems in the south fed from the Australian Alps. To the east and south, the highlands of the Great Dividing Range form the limit of the Murray–Darling Basin region, while in the north, west, and southwest the boundaries are much less distinct. The greater proportion of the Murray–Darling Basin region is made up of extensive plains and low undulating areas; most of them are less than 200 m above sea level.
As shown in Figure R2, major rivers in the Murray–Darling Basin region include:
- The Darling River, which begins in northern New South Wales and with its major tributaries (including the Culgoa, Balonne, and Condamine rivers) flows for 2,740 km southwest to its junction with the River Murray at Wentworth.
- The River Murray, which forms the border of Victoria and New South Wales, and flows east to west for 2,530 km.
- The Murrumbidgee River, which flows 1,575 km from southern New South Wales through the Australian Capital Territory and then westwards to the River Murray.
- The Lachlan River, which starts in the central highlands of New South Wales and flows 1,339 km southwest to the Murrumbidgee River.
- The Goulburn River, which flows 654 km from central northern Victoria northwards into the River Murray (Geoscience Australia 2015).
Figure R2 Contextual map of the Murray–Darling Basin region showing the major rivers and towns
Region definition
The Murray–Darling Basin region is defined in Section 18A of the Australian Government Water Act 2007 (the Act). It includes all water resources within or beneath the Murray–Darling Basin region but does not include groundwater that forms part of the Great Artesian Basin (GAB). The GAB, not included in the Murray–Darling Basin region as it has its own management arrangements, is only partly overlapping with the region and partly connected hydrologically; therefore, it is specifically excluded under the Act.
The 2016 Account, adopts the geographical boundary definition as specified in s.18A of the Act for the Murray–Darling Basin region (see Figure R2) except:
- the areas draining into the Snowy Mountains Hydroelectric Scheme storages that are located within the geographical boundaries of the Murray–Darling Basin as specified by the Act, and
- the towns of Port Elliot and Middleton in South Australia.
These exclusions align the National Water Account Murray–Darling Basin region boundary to the Murray–Darling Basin Authority (MDBA) operational area boundary.
The region includes water stored in and transactions related to:
- surface water storages in the region
- rivers within the region
- groundwater aquifers beneath the region.
The region excludes water stored in and transactions related to:
- water held in off-channel water storages, such as landscape catchment storages (also known as farm dams and run-off dams) used to harvest runoff and floodwaters (these constitute water abstracted before it reaches the rivers or water owned by the users)
- water held in the landscape, such as soil moisture
- water held in irrigation scheme channels and pipes
- urban water systems at utility level and private water supply systems.
As a consequence of differences in spatial coverage, volumetric information provided for the ACT water resource plan area in the Murray–Darling Basin region account (this account) can differ to volumetric information provided in the water account for the Canberra region. The Canberra region water account incorporates the whole of the ACT water resource plan area and a part of the NSW Murrumbidgee water resource plan area. Information for these two planning areas is provided separately in the Murray–Darling Basin region water account.
For more information regarding inclusions and exclusions in this water accounting report, please refer to the Water accounting policies note.
Land use
The major population centres of the Murray–Darling Basin region and their population are:
- Canberra–Queanbeyan: 391,500
- Toowoomba: 96,600
- Bendigo: 82,800
- Albury–Wodonga: 77,200
- Wagga Wagga: 46,900
- Shepparton: 42,700
- Tamworth: 36,100
- Orange: 35,000
- Mildura–Buronga: 33,400
- Dubbo: 32,300
- Bathurst: 31,300 (ABS 2011).
Note: The population numbers above are related to major urban centre / locality. There are also a number of smaller urban centres throughout the Murray–Darling Basin region such as Griffith, Echuca, Moree, Horsham, Wangaratta, Warwick and Murray Bridge.
The Murray–Darling Basin region is one of the productive agriculture regions in Australia. It contains approximately 40% of all Australian farms (by number) that produce rice, cotton, grapes, wool, wheat, hay, fruits, products from sheep and livestock, dairy products, oilseeds, wine, and vegetables for domestic and overseas markets (Murray–Darling Basin Authority [MDBA] 2016a).
The major land use activities in the Murray–Darling Basin region are shown in Figure R3. Land use classifications were derived from Australian Government Department of Agriculture and Water Resources (2017) sources. Irrigated agriculture and urban supply are two of the major water users in the Murray–Darling Basin region. A more detailed breakdown of land use type and area for the Murray–Darling Basin region is provided in the downloadable table.
Figure R3 Land use in the Murray–Darling Basin region
Source: Interpreted from Australian Government Department of Agriculture and Water Resources (2017).
The Murray–Darling Basin region contains 70% of Australia's irrigated land area (Murray–Darling Basin Authority 2016a). The major irrigation areas in the region include Murrumbidgee, Coleambally and Murray in New South Wales and the Goulburn–Murray in Victoria. For more information on these major irrigation schemes, refer to Murrumbidgee Irrigation, Coleambally Irrigation, Murray Irrigation and Goulburn–Murray Water websites. In addition to these major irrigation schemes, there are many relatively minor irrigation schemes. There is also an extensive infrastructure to supply water to irrigation water users from these irrigation schemes. This infrastructure links rivers and channels with the storages designed for irrigation water supply. Further information for irrigation water supply within the Murray–Darling Basin region is provided under the Economic benefits section of the 'Water access and use' note.
Figure R4 provides details of the irrigation areas within the Murray–Darling Basin region.
Figure R4 Irrigated areas within the Murray–Darling Basin region
(Map sources: Geoscience Australia irrigation gazetted areas and ABARES land use map)
Significant aquatic ecosystems
The Murray–Darling Basin region contains 16 Ramsar-listed wetlands of international importance (Australian Government Department of the Environment 2016a). These wetlands are shown in Figure R5.
Figure R5 Ramsar wetlands in the Murray–Darling Basin region
The Murray–Darling Basin region contains a further 30,000 wetlands in total, over 100 of which are listed as nationally important in the Directory of Important Wetlands in Australia (Australian Government Department of the Environment 2016b). Most 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. The focus of The Living Murray program—a joint partnership between the Murray–Darling Basin Authority, Australian Government and Basin State and Territory Governments—is to improve the environmental health of these sites through environmental watering (both planning and delivery) and monitoring, to ensure Australian communities can continue to enjoy the River Murray for years to come.
Significant Indigenous cultural places and practices
The Murray–Darling river system has been and continues to be of high importance to Aboriginal people, and their history in the Murray–Darling Basin region extends over at least 45,000 years to the present day. 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, wetlands and other resources. The rivers and flood plains are of particular importance to the traditional cultural beliefs and practices of Aboriginal nations. Today there are almost 50 Aboriginal nations whose traditional lands are within the Murray–Darling Basin (Murray–Darling Basin Authority 2016a).
Archaeological evidence can be found including such things as shell middens, quarries, rock shelters with archaeological deposits (e.g. stone artefacts), open campsites, rock paintings and engravings, axe-grinding rocks with their grooves, burial grounds, and the sacred and ceremonial sites. The sites are dated from a range of ages:
- 9,000–13,000 years old: the Kow Swamp burial site in northern Victoria
- at least 20,000 years old: excavations indicating Aboriginal presence at Keniff Cave, at the headwaters of the Darling River
- approximately 40,000 years old: evidence of Aboriginal populations from Lake Mungo and other lakes of the Willandra system. Willandra Lakes area's historical significance was recognised with its World Heritage listing in 1981
- of more recent origin: the many carved and scarred trees from which bark canoes, shields, boomerangs and carrying dishes were cut. These trees can be found along most of the Murray–Darling Basin's waterways.
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. The rivers have always been of great importance to the Aboriginal people, especially as sources of food. As an example, the fishtraps of the Ngemba in the Barwon River at Brewarrina illustrate how the river serves as a critical source of food. Brewarrina is well known for the 40,000-year-old Aboriginal fishtraps that are located just below the weir in the Brewarrina township. These traps are constructed from carefully placed rocks in a circular arrangement and are still used today.
Water resources
The water resources in the Murray–Darling Basin region are highly developed, as illustrated by the following statistics:
- As a long-term average, 42% of the total surface water runoff to the Murray–Darling Basin region is diverted for consumption or environmental management purposes.
- Most of the surface water consumed in the Murray–Darling Basin region, 10.9 million ML/year on average, is diverted from watercourses and used for irrigation and urban water supply. In addition, 2.7 million ML/year of runoff is intercepted by local catchment storages and forestry plantations before it reaches the watercourse.
- Approximately 1.8 million ML of the Murray–Darling Basin's groundwater resources are consumed each year; however, due to the abundance of surface water resources, a lower volume has been consumed in recent years. The majority of groundwater use is centred on a small number of large alluvial aquifers in New South Wales, Queensland, Victoria, and South Australia where the groundwater is used for agricultural purposes. Elsewhere, there are areas in the Murray–Darling Basin where groundwater is the only reliable source of water for stock and domestic uses.
The Murray–Darling Basin Cap (the Cap) was established in 1995 to limit the volume of surface water that could be diverted in the Murray–Darling Basin region in any year to that based on the 1993–1994 levels of development. The Cap does not place a restriction on groundwater extraction; however, the Basin Plan (Murray–Darling Basin Authority 2016b) has now established sustainable diversion limits (SDLs) for both surface water and groundwater use within the Murray–Darling Basin region.
Surface water
The storages within the Murray–Darling Basin region are shown in Figure R6. The northern part of the Murray–Darling Basin region consists mostly of unregulated systems although there are major storages in the rivers including Border, Gwydir, Namoi and Macquarie. Many of the rivers and streams in the northern Murray–Darling Basin region are ephemeral and flow for a short period following precipitation. Generally, water users in much of the northern Murray–Darling Basin region rely on collecting water during floods and storing it on-farm for later use.
The southern part of the Murray–Darling Basin region is mostly a regulated system with major storages in many 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.
The total storage capacity for the 56 major storages (excluding weirs not considered as storages) within the Murray–Darling Basin region is 23,161,755 ML. A full list of these storages and their individual total storage capacities can be found in the downloadable table under Surface water assets.
Further information on the water storages across the Murray–Darling Basin region, including current levels and volumes, is available from the Bureau of Meteorology's Water storage website.
Figure R6 Major storages in the Murray–Darling Basin region; capacity of each storage is also shown
Rivers
The gauging stations used to represent streamflow conditions within the Murray–Darling Basin region water account are:
- The River Murray at Doctors Point at Albury (Station 409017), which represents a regulated reach of the Murray downstream of major regulating storages within the southern part of the region.
- The Darling River at Bourke (Station 425003), which represents the unregulated northern part of the region.
- Ovens River at Peechelba (Station 403241), which represents a largely unregulated major river within the southern part of the region.
Figure R7 shows mean monthly flow at three gauging stations and mean monthly rainfall across the region. The locations of the gauging stations are shown in Figure R8, and information on monthly flow volumes and variations for the flows at these three gauging stations is available in Streamflow section. There are several gauging stations along these rivers although they are not shown on this map. Further information on other gauging stations across the Murray–Darling Basin region is available from the Bureau of Meteorology's Water Data Online website.
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
Figure R8 Key flow gauging station locations along the main rivers within the Murray–Darling Basin region
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, as shown in Figure R9.
Figure R9 Water transfers into, out of and between catchments within the Murray–Darling Basin region
Transfers into the Murray–Darling Basin region are from:
- the Snowy Mountains Hydro-Electric Scheme into the Murrumbidgee and Murray rivers (see Inter-region claim for more details)
- the Glenelg catchment to the Wimmera system
- the Cressbrook reservoir to Toowoomba and surrounds.
Transfers out of the Murray–Darling Basin region are 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
- the Goulburn River system via the North–South Pipeline for distribution to Melbourne
- water transfers from the Goulburn River system to Ballarat (in the Barwon River basin) via the Goldfields Superpipe since May 2008
- water transfers from the Goulburn River system (from Silver and Wallaby creeks, which are tributaries of the Goulburn River, not shown in Figure R9) to the Melbourne urban supply system.
Internal transfers between catchments
Channels and pipelines in the river system of the southern part of the region 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 (including the Lower Murrumbidgee and the South Australian Murray)
- the shallow aquifers of the Darling River Basin overlying the GAB (including the Lower Namoi and Gwydir)
- valley-fill alluvium (including the mid-Murrumbidgee, Upper Namoi and Upper Lachlan) in the highlands bordering the region
- the local fractured rock aquifers of the Great Dividing Range and other areas where the basement rock outcrops.
While the GAB is a major groundwater resource under the Murray–Darling Basin, it is not included in the 2016 Account. The boundaries of the groundwater systems do not align with those of the Murray–Darling Basin, which is defined on the basis of its surface water resources. Also the aquifers are different and not fully connected to MDB hydrologically.
The different groundwater systems behave somewhat independently of each other, with only relatively small volumes of groundwater directly flowing from one system to another; however, water from different aquifer systems is transferred across boundaries as surface water base flow. Through this process, a substantial volume of groundwater enters the surface streams 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).
The sedimentary aquifers within the region cover the main depositional areas of the Murray and Darling river basins including upstream reaches of other major rivers such as the Murrumbidgee and the Namoi. The major aquifers within or at the peripheries of the Murray geological basin include the Shepparton, Calivil, Parilla–Loxton Sands, Murray Limestone, and Renmark Group aquifers and the upland alluvium of the Cowra and Lachlan formations. The important alluvial sediments of the Darling River basin include the Gunnedah and Narrabri aquifers. An example of aquifers across the southern basin of the Murray–Darling Basin is shown in Figure R10.
Figure R10 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 extraction, with nearly all of the extracted groundwater (more than 95%) coming from these aquifers. They have relatively high water-holding capacity and hydraulic conductivity and therefore are suited for extraction for use in irrigation and urban water supply. Most of the groundwater reported in the 2016 Account was from these aquifers. Groundwater quality typically deteriorates along the groundwater flow path, constraining groundwater use to areas with acceptable water quality (primarily determined by low salinity).
The GAB is the largest groundwater basin in Australia. It underlies about one third of the Murray–Darling Basin (Figure R2) and extends beyond the Murray–Darling Basin drainage basin boundary to the north and west. The GAB contains confined aquifers at depth, with confining layers that can be at or near the land surface. The GAB provides vital water resources for domestic and town water supply, for stock use by the pastoral industry, and water supplies for the operations of mining and petroleum industries and associated communities. 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. Groundwater extraction and leakage from the GAB to the Murray–Darling Basin are not represented in the 2016 Account, but may be represented in future accounts as an inter-basin transfer.
Fractured rock aquifers occur in the highland areas around the peripheries of the Murray–Darling Basin region (see Figure R10). In fractured rock aquifers, groundwater is stored in the fractures, joints, bedding planes and cavities of the rock mass. Due to the difficulty of obtaining high yields from most fractured rocks, the volume of groundwater extracted from any one bore and in a given area is relatively low. In most fractured rock areas of the Murray–Darling Basin, groundwater use is limited to stock and domestic supply. It is considered that the annual change in groundwater storage and annual groundwater flow out of fractured rock areas is of low significance to regional water balance and they are not estimated in the 2016 Account.
Other water resources and systems
Farm dams
Farm dams (run-off 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 (see Region definition).
In the Murray–Darling Basin region there are over 650,000 farm dams (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 majority of the region's farm dams are filled by rainfall–runoff capture; a smaller portion of farm dams are filled by groundwater extractions and surface water diversions. The water held in these farm dams is primarily used for agricultural and for stock and domestic purposes.
As farm dams represent an important water resource in the Murray–Darling Basin region, further information on farm dams is presented under the Landscape water rights section of the 'Water access and use' note.