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Barwon–Darling

The Barwon–Darling river system is in north-western New South Wales. It takes in the Barwon River, from upstream of Mungindi at the confluence of the Macintyre and Weir rivers, to where the Barwon meets the Culgoa River. At this point the river channel becomes the Darling River and the Barwon–Darling system extends downstream to the Menindee Lakes.

The catchment of the Barwon–Darling covers about 13% of the Murray–Darling Basin. The catchment only generates about 2.8% of the flow in the Basin, however much more water flows through the system, 99% of its flow is generated in upstream catchments. The region uses 3% of the total surface water diverted for irrigation in the Basin and less than 1% of groundwater used. The Barwon–Darling is unregulated, except for some low-level weirs near townships, but many of the tributaries of the system are highly regulated.

The Barwon–Darling corridor connects all the rivers, lakes and wetlands in the northern Basin; and then provides a connection to the southern Basin through the lower Darling River. The river system provides habitat during dry periods and travel pathways in the semi-arid inland. There are many billabongs and lagoons along the Barwon–Darling corridor, as well as lakes and wetlands on the floodplains, which provide major bird breeding sites.

There a several small towns in the region servicing rural communities and agricultural enterprises. The major land use is dryland grazing of cattle for beef and sheep for wool. A small area of land is irrigated and mainly supports cotton production. Crops are irrigated by supplementary water from large on-farm storages on the western plains, which is harvested from upstream tributary flows. Almost one-third of the catchment area remains as native vegetation.

Snapshot

Catchment area

13% of the Murray–Darling Basin

Contribution to Basin water

2.8%

Annual stream flow

3,500 GL (Bourke)

River length

1,600 km (approx.)

Tributaries

Border Rivers, Moonie, Culgoa (Condamine), Bokhara, Gwydir, Namoi, Castlereagh, Macquarie and Bogan rivers; Paroo and Warrego in high flow years

Towns include

Collarenebri, Walgett, Brewarrina, Bourke, Cobar, Wilcannia

Major water storages

None

Water users

Urban water supply, stock, domestic and irrigation

The landscape and its water

The Barwon–Darling river system is effectively the stem of a funnel for the upper catchments of the Basin, providing the connection between the northern and southern basins.  

The Barwon River flows south-west through a relatively narrow floodplain with a tightly meandering channel and a highly-variable flow pattern and capacity. Capacity is significantly increased downstream of Collarenebri, after the Little Weir, Boomi, Moonie, Gwydir and Mehi rivers have joined the Barwon. Riverine woodlands are the most common vegetation community along the banks and associated wetlands of the Barwon–Darling river system, and are dominated by river red gum.

After Collarenebri, the Barwon River continues south-west, and is joined by more creeks and rivers. Beyond the floodplains of the river, north and upstream of Brewarrina, are large areas of open semi-arid eucalypt woodlands, featuring a variety of species including poplar box, white cypress pine, ironwood and mulga. Beyond Walgett the river turns in a westerly direction and flows unrestricted across alluvial plains. It becomes less sinuous but there are many anabranches and effluent channels which split and rejoin the major channel. Upstream of Bourke, the Barwon merges with the Culgoa River, and the channel becomes the Darling River.

The Darling River flows south-west within a deeply incised channel towards Wilcannia. Belah woodlands occur on the floodplain, featuring rosewood, sugarwood and wilga. Below Wilcannia the Darling reaches the Menindee Lakes, at the artificial storage of Lake Wetherell. Beyond this point the catchment is the Lower Darling.

The highly variable flows in the Barwon–Darling are driven by tributaries carrying water from many catchments of northern New South Wales and southern Queensland, including the Paroo, Warrego and Condamine–Balonne rivers in the north and west, and the Moonie, Border Rivers, Gwydir, Namoi, Macquarie–Castlereagh and Bogan rivers to the east and south. Some of these waterways only reach the Barwon–Darling after major floods.

The Barwon River starts at an elevation of about 200 m, at the confluence of the Macintyre and Weir rivers, and flows about 700 km over a low gradient to an elevation of 110 m at its confluence with the Culgoa River. From this point, the Darling River flows another 900 km to the Menindee Lakes, at which point the elevation is less than 100 m.

The Barwon–Darling region has a semi-arid climate and rainfall is low throughout the year, but peaks in summer, with an annual average of 330 mm.

Groundwater in the catchment is contained in the Darling Alluvium associated with the Darling River; fractured rock aquifers associated with the Lachlan Fold Belt, shallow aquifers of the Great Artesian Basin and deep aquifers of the Great Artesian Basin.

People, industry and water use

The Barwon–Darling catchment includes the land of many Aboriginal nations including the Barkindji, Murrawarri, Ngemba and Ngiyampaa. The connection of Aboriginal people to the region dates back tens of thousands of years. One of the oldest human-made structures on earth is at Brewarrina on the Barwon River, where Aboriginal people built extensive and intricate stone fish traps.

European settlers came to the district and established pastoral grazing in the 1840s. In 1859, Captain W.R. Randall sailed the Gemini from South Australia up the Darling River to Bourke, thus beginning a long period of river transport and trade, peaking in the late 1800s when more than 40,000 bales of wool were shipped down the Darling each year. Bourke, Brewarrina and other centres on the Darling became vital transport hubs for the whole of south-west Queensland and western New South Wales and commercial river transport continued until 1931.

Copper was discovered at the Cobar mining belt in 1869, where exploration continues today. The region is one of the largest concentrations of base metals in Australia, and includes lead, zinc, silver and gold. The opal mining industry began in Lightning Ridge in 1901.

The Barwon–Darling region has a population that makes up less than 1% of the total population of the Basin. The main towns of the catchment are Cobar, Bourke, Walgett, Wilcannia and Collarenebri.

The major land use in the catchment is agriculture; and the main industry is beef and sheep grazing on pastoral land, and cotton production on the western plains near the river. There is increasing development of land for grazing and intensive cropping in the eastern margin of the region. While cotton is the dominant irrigated crop in the region, there are several other enterprises including fruit, nuts and grapes. Tourism, retail and the service industries are the next largest contributors to the region’s economy, followed by mining in Cobar and Lightning Ridge.

The Barwon and Darling rivers are unregulated, with no major public water storages in the catchment, but many of their upstream tributaries are highly regulated. The region uses 3% of the total surface water diverted for irrigation in the Basin and groundwater use is less than 1% (excluding water use from the Great Artesian Basin). Irrigation is almost entirely from surface water diversion.

Regulation of water in the catchment

In 1968, the naturally occurring chain of lakes near Menindee on the Darling River was modified by the NSW Government to improve its storage capacity for farming, recreation, mining and urban water supply, and to manage Darling River floods. There are many small and medium-sized weirs along the Barwon–Darling: public storages to secure water supply for towns and private storages to supply properties. On-farm water storages are dispersed along the length of the river, which harvest overland flows and diversion of the river when flows permit. Harvested water is stored in large shallow floodplain storages known as ‘ring tanks’ or ‘turkey nest dams’. 

Environmental importance

The Barwon–Darling corridor is unique in its vital role connecting all the rivers, lakes and wetlands in the northern Basin. It provides habitats during dry periods and travel pathways connecting the northern valleys of the Basin, as well as connecting the northern and southern basins.

The Barwon–Darling is recognised for supporting populations of native fish, which are excellent indicators of the health of rives and their catchments. It is an ecologically significant area, featuring wetlands including the Wongalara, Woytchugga and Poopelloe lakes, the Acres Billabong and several deflation basin wetlands. There is also the nationally important wetland area Talyawalka Anabranch and Teryawynia Creek, near the southern boundary of the Barwon–Darling region, located between Wilcannia and Menindee on the Darling Riverine Plains. Listed in the Directory of Important Wetlands in Australia, it is a semi-arid inland floodplain wetland system fringed by black box woodland. These wetland systems all provide habitats for major breeding sites of more than 10,000 waterbirds, including threatened species such as the blue-billed duck and brolga. Other threatened and protected bird species within the region include the grey falcon and superb parrot.

A wide variety of ecosystems and a number of fish species, including the golden perch, are supported by the river channel and riparian habitats. Vulnerable or endangered species such as the Murray cod, silver perch and freshwater catfish, have been recorded amongst the 21 species of fish in the lower reaches of the system and its tributaries. Increasing numbers of carp have had a significant impact on native fish, however there are healthy communities of turtles, mussels, shrimp and other aquatic species to indicate a healthy river system. Significant fauna species are found in the catchment include river red gum, black box, river cooba, coolabah and lignum.

The Ngemba Billabong at Brewarrina contains 40,000 year old fish traps, and was declared an Indigenous Protected Area in November 2010. It is also a declared a World Conservation Union (IUCN) Category V and VI protected area.

In the Sustainable Rivers Audit 2 released in 2012, the study area of the Darling River valley included the narrow upper valley of the Barwon–Darling river system, through to the wide floodplain regions of the mid and lower Darling River. The audit reported that the overall ecosystem health of the Darling valley was poor. The fish community had lost half of its native species richness, and was rated poor in the lower and middle zones and moderate in the upper zone; while the macroinvertebrates were rated poor overall. Riverine vegetation in the region is notable for being in near-reference condition across the zones, with each being rated in good condition. There was little evidence of the main vegetation groups being cleared or damaged, however there were some modifications noted near the main river channels. The physical form of the river system was rated in moderate condition, but there was accelerated floodplain sedimentation in the upper zone and channel enlargements in the lower zone, since European settlement. The overall rating of hydrology of the Darling was moderate, as flow volumes, seasonality and variability has changed markedly in the mainstem of the river system. However, there was little change from reference condition for high over-bank floods and low or zero flows.

Water recovery

The Basin Plan sets Sustainable Diversion Limits, which is how much water can be used in the Murray–Darling Basin, while leaving enough water for the environment. A Sustainable Diversion Limit (SDL) was established for each catchment (or group of catchments) and the reduction in diversions required to achieve the SDL was identified.

The use of environmental water in a specific catchment or region will vary from year-to-year. The MDBA has a Basin-wide environmental watering strategy to guide the use of environmental water across the Murray–Darling Basin to help achieve the best possible results over the long term. Environmental water managers make the day-to-day decisions on what to water and when, in line with the strategy and taking into account seasonal conditions, priorities and the availability of environmental water. Watering decisions are made in consultation with various waterway managers and local landholders.

Catchment or regionally-specific details about environmental water use in the catchment including watering actions, portfolio details and planning, and monitoring of environmental watering, can be found through the Commonwealth Environmental Water Holder or the state government environmental water manager. 

More information

Water management

The management of water resources is the responsibility of local, regional, state and Australian governments.

Delivery to households, industry and farms is managed by local councils or regional water authorities.

State government departments for water ensure the network of authorities manages water responsibly and fairly, that catchment and waterway health is maintained or improved through catchment management authorities, and that water saving, re-use and flood management projects are implemented. State governments must manage their state's water resources according to state and commonwealth water legislation.

In addition to directing operations of the regulated River Murray system, the MDBA implements a number of plans and programs to ensure the waters of the Basin, which flow through four states and one territory, are managed cohesively and in the best interests of all water users of the Basin. 

Rural water authority

Urban water authority

Catchment management authority

State government water

Use of environmental water

Irrigation water allocation

Maps