The Great Cumbung, August 2013. Photo: CEWO
The Lachlan River flows through the lands of the Nari Nari, Ngiyampaa, Wiradjuri and Yita Yita Nations, and the Commonwealth Environmental Water Office respectfully acknowledges these people, their Elders past, present and future, as the Traditional Owners of the land.
The Lachlan River is the fourth longest river in Australia at 1,448 kilometres, starting near Goulburn in the Great Dividing Range at an elevation of around 1,200 metres and terminating at The Great Cumbung near Oxley. Its waterways are a source of water for stock and domestic and agriculture use, tourism and recreational activities and Aboriginal cultural values and practices.
The Lachlan River system, floodplains, swamps and wetlands provide habitat for birds including straw-necked ibis, glossy ibis, egrets, Australian painted snipe, osprey and blue-billed duck, and a range of native fish including Murray cod, golden perch, silver perch, eel-tailed catfish and an endangered population of olive perchlet. These wetlands also feature areas of valuable river red gum forest and woodlands, blackbox woodland and lignum. The lower Lachlan floodplain is home to 9 nationally important wetlands, including Lake Brewster, the Booligal Wetlands and The Great Cumbung. The Great Cumbung, covering 20,000 hectares, contains one of the largest remnant examples of common reed (Phragmites australis) swamps and stands of river red gums in NSW.
For more information, please see the Water Management Plan 2021-22: Chapter 11 - Lachlan River.
Map of the Lachlan River catchment, New South Wales, Australia.
Delivery of environmental water to date
The use of Commonwealth environmental water in the Lachlan catchment commenced in 2010-11. At that time, and despite the first significant natural flows in more than a decade, the catchment was severely impacted by the millennium drought. Post millennium drought high natural flows (which triggered translucent flows, see below) and large-scale environmental watering events improved the conditions in the lower Lachlan catchment. Further high rainfall in winter and natural flooding in spring 2016 created wide scale inundation of the floodplain and wetlands in the mid to lower Lachlan further improving the catchment’s post-millennium drought condition.
Over the last several years the Lachlan catchment has been impacted by lower than average rainfall which has resulted in a drying of the catchment. During the second half of 2020-21 wet conditions returned to the catchment and continuing into the start of 2021-22. During 2021-22, watering actions may seek to complement other flows in the system to maintain the health of floodplain vegetation, maintain water quality where feasible to do so and/or the support waterbird breeding events.
A summary of Commonwealth environmental water use in the Lachlan catchment is available on the History tab.
What is a translucent flow?
Under the approved rules that govern management in the regulated Lachlan River, if a certain amount of water (250,000 ML since 1 January of each year) flows into the Wyangala Dam, water from tributaries or a volume released from storage is allowed to flow the length of the river over the period 15 May to 15 November. This is called a translucent flow and is a type of planned environmental water event that is intended to restore some medium to high flows, seasonality and flow variability. Translucent flows can be an important contributor to the health of the Lachlan catchment because water from tributary inflows is generally richer in nutrient than water released from the dams.
Above: a larval Murray cod found by CEWO’s monitoring team near Hillston in the lower Lachlan. Photo: University of Canberra
What has environmental water achieved in the Lachlan?
Scientific monitoring conducted under the Commonwealth Environmental Water Office’s monitoring programs shows that environmental watering helps to improve the condition of the system through the targeted delivery of water to maintain fish condition, movement and breeding, maintain waterbird breeding habitat, maintaining connectivity and variability of flows along the river and improving the health and condition of aquatic and riparian vegetation.
A summary of the results for the last water year is provided below. More information is also available from the full monitoring reports published each year.
In partnership with NSW, Commonwealth environmental water was used in seven watering actions during 2020-21. These included the August-September Brewster translucent flow, November- December Wyangala translucent flow, an in-channel autumn pulse in conjunction with NSW Environmental Water Allowance, Booberoi Creek spring pulse, Fletchers Lake. Lake Brewster and the Noonamah black box woodlands. A summary of Commonwealth environmental water use in the Lachlan catchment is available at the History tab.
Meeting of landholders, researchers and water holders in the lower Lachlan, August 2019. Photo: CEWO
Commonwealth environmental water use is planned, delivered and managed in partnership with a number of individuals and organisations in the Lachlan River valley including:
- New South Wales Department of Planning, Industry and Environment
- New South Wales Department of Industry – Water
- Central West Local Land Services
- Central Tablelands Local Land Services
- New South Wales Department of Primary Industries – Fisheries
- Lachlan Environmental Water Advisory Group
- University of Canberra
- University of New South Wales