The Lachlan River is the fourth longest river in Australia. The river runs from the Great Dividing Range in central New South Wales, westwards through sloping country in the central catchment, and then across river plains. The river ends at the Great Cumbung Swamp. In times of high flow, water will continue southwards through the swamp to reach floodwaters of the Murrumbidgee River.
The wetlands of the Great Cumbung Swamp, are extensive and unique. Extraction rates in the catchment are high, and combined with naturally high evaporation rates and the impact of the millennium drought, flows into the wetlands have been very low over recent decades.
The catchment is home to about 4% of the population of the Murray–Darling Basin, and the income of the population is primarily derived from agriculture and the supporting industries and services in regional centres.
Snapshot
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Catchment area
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8% of the Murray–Darling Basin
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Contribution to Basin water
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6.5%
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Annual stream flow
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834 GL per year (Cowra)
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River length
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1,339 km
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Tributaries
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Abercrombie, Belubula, Boorowa rivers; Mandagery Creek
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Towns include
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Boorowa, Cowra, Canowindra, Forbes, Hillston
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Water storages
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Wyangala (1,220 GL), Lake Cargelligo (36 GL), Carcoar Dam (36 GL)
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Water users
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Urban water supply, stock and domestic, irrigated agriculture, mining
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The landscape and its water
The headwaters of the Lachlan River are on the Breadalbane Plain between Yass and Goulburn, on the Great Dividing Range in central New South Wales. The river flows north and then west through diverse landscape ranging from temperate forests, woodlands and grasslands in the east to semi-arid woodlands, mallee and scrublands in the west.
The eastern end of the catchment has elevations up to 1,400 metres and an annual average rainfall in these cooler regions ranges from 800–1,000 mm. The western end of the catchment is located on warm-hot semi-arid plains, at an elevation of around 200 m, and an annual average rainfall of 300 mm. Monthly rainfall is fairly similar across the year.
Groundwater in the catchment exists in alluvial deposits that extend along the Lachlan River from Cowra to Condobolin, as well as along tributaries of the Lachlan. However, the main resource of good quality (fresh) groundwater is in alluvial aquifers that spread across the western part of the catchment from Lake Cargelligo to beyond Hillston – an area of around 3,300 km². There is streamflow leakage into alluvial groundwater within the catchment, which is expected to increase with increased groundwater use in the upper catchment.
People, industry and water use
The traditional people of the slopes and plains of the Lachlan catchment are mainly the Wiradjuri, whose nation is the largest Aboriginal Nation in New South Wales, and extends from the River Murray to beyond Dubbo, and west to Balranald. Other parts of the catchment are the traditional lands of the Nari Nari, Ngiyampaa and Yita Yita nations.
European settlement of the Lachlan River catchment began in the 1830s, with the establishment of pastoral landholdings, and cropping began in the 1860s with a focus on wheat production. The wheat industry gave rise to milling and transport infrastructure, and additional fodder and grain crops such as oats, rye, maize and barley were established. Market gardening and fruit orchards in the upper Lachlan took advantage of the transport connections to Sydney, and a canning plant was established at Cowra in the 1940s. Viticulture was identified as a potentially productive activity at the turn of the 20th century, and a wine industry was established by the 1920s.
The Lachlan catchment is home to about 4% of the population of the Murray–Darling Basin. The main towns or cities in the catchment service rural industry and the rural population, however residents often travel to larger centres in neighbouring catchments for some health, education and business services. The main centre of Cowra and Parkes have a population of about 10,000 people (ABS 2011) and Forbes has 7,000. Agriculture or rural industries provide the main source of employment in the catchment.
Agriculture is the main industry of the catchment, using more than 80% of the land. The slopes and eastern plains support dryland cereal production and livestock grazing, while the tablelands and western plains support dryland grazing. Land along the river is irrigated for the production of fruit, vegetables, cotton, rice, fodder crops and cereal grains. Dairying, feedlots and piggeries also depend on river water.
The Commonwealth Scientific and Industrial Research Organisation (CSIRO) reports that 28% of available surface water was extracted for use, which is moderately high compared with other catchments in the Basin. Groundwater use, on average, makes up 45% of all water used in the catchment annually, and mainly used in the lower catchment around Hillston for irrigation.
Regulation of water in the catchment
The Lachlan River was regulated as part of the development of inland New South Wales in the early 20th Century. The Wyangla Dam, near Cowra, was constructed in 1935 and the Jemalong Weir at Forbes was constructed in 1939 – both to provide a regulated source of water to towns along the river and to irrigators. After significant floods in the 1950s, and a burgeoning lucerne industry in the valley through the 1950–1970s, Wyangla Dam was enlarged from 360 gigalitres (GL) to 1,200 GL in 1970. A number of natural lakes in the catchment were dammed to store water in the lower catchment, including Lake Cargelligo and Lake Brewster. There are many other small weirs on tributaries of the Lachlan, as well as on the lower Lachlan.
Environmental importance
The Lachlan River and its floodplains provide a wide range of aquatic habitats such as pools, backwaters and billabongs, instream woody habitat and aquatic plants. The lower Lachlan floodplain has 9 nationally important wetlands, including Lake Brewster, the Booligal Wetlands and the Great Cumbung Swamp. The latter features one of the largest stands of river red gums in New South Wales and is one of the most important waterbird-breeding areas in eastern Australia.
The Sustainable Rivers Audit 2 reported that the overall ecosystem health of the Lachlan River Valley was very poor. Drought had severely affected species abundance and diversity of fish, with the health of the fish community rated extremely poor. The macroinvertebrate community was rated as moderate condition throughout the valley. Riverine vegetation was rated as poor condition in the valley overall; however condition was good in the lowlands zone but very poor in the slopes, upland and the montane (lower mountain) zones. The physical form of the river was rated good but there was widespread channel straightening and enlargement, in the slopes zone in particular. Sediment loads have also increased since European settlement. Flow seasonality and variability was rated moderate in the valley overall, but poor in the lowland zone where flows were impacted by seasonality and extraction of supply for irrigation.
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 Murray–Darling Basin Authority (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 4 states and 1 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
