Lachlan Valley environmental water
Straw-necked ibis and freckled ducks in Booligal Wetlands, Lachlan Valley, during spring 2010. Freckled ducks are listed as vulnerable in NSW. Following an environmental water release, four pairs of these ducks nested and bred in dense lignum that also supported nesting of over 60,0000 pairs of straw-necked ibis. Photo: Paul Packard, OEH.
The Lachlan catchment has an area of 90,000 square kilometres, extending from the Great Dividing Range to the Great Cumbung Swamp on the Riverine plains. The Lachlan has three areas of particularly high environmental value:
Great Cumbung Swamp
- Lachlan Swamp.
All are listed in the Directory of Important Wetlands in Australia. Other significant wetlands include Merrowie Creek Wetlands, Lake Brewster and Lake Cowal. The Lachlan River, and wetlands in particular, hold important Aboriginal cultural values.
View a map showing the location of environmental watering areas in the Lachlan valley (Lachlan2013.pdf, 845KB).
Benefits of environmental water
Environmental water in the Lachlan supports:
wetland plant communities, including black box, river cooba, common reed, extensive areas of riparian fringing river red gum forest - the Great Cumbung Swamp has one of the largest stands of river red gum in NSW
- waterbird breeding and foraging habitat - in good condition, the Lachlan wetlands and floodplains support breeding events for tens of thousands of colonial nesting birds, such as straw-necked ibis and glossy ibis; when water levels are suitable, Lake Brewster supports large breeding colonies of pelicans
- habitat for birds listed under international migratory bird agreements, including great egret, glossy ibis, sharp-tailed sandpiper, common greenshank, Latham’s snipe, painted snipe and white-bellied sea-eagle
- habitat for birds listed as vulnerable, including the Australasian bittern, blue-billed duck and freckled duck
- maintenance of drought refuges for water birds
- maintenance of fish refuges and variable flow conditions, which are required by native fish to breed and disperse
- wetlands listed as endangered ecological communities, including the lowland section of the Booligal Wetlands, the Great Cumbung Swamp and Lachlan Swamps.
Catchment condition 2012-13
In early 2012 substantial inflows to Wyangala and Carcoar Dams resulted in dam spills, with inflows sufficient to trigger the release of translucent flows under the water sharing plan and the filling of wetlands in the mid and lower Lachlan. Despite the 2012 flood conditions and the application of planned environmental water, the mid and lower Lachlan floodplains and wetlands are now dry again, with only the deeper or more reliably inundated areas still holding water.
Though the condition of Lachlan wetlands varies considerably across the catchment, the lower Lachlan floodplain has significantly improved in health from that experienced during the Millennium Drought.
Available environmental water in 2012-13
Moderate conditions currently exist in the Lachlan catchment. At the start of the water year Wyangala Dam was at 68% capacity, while Carcoar Dam was at 63%, with high security allocations at 100% and general security allocations at 0%. However, general security account carryover provides around 71,000 ML of held environmental water made up from NSW Environmental Water Holdings and Commonwealth environmental water for use in the Lachlan valley this water year. A further 40,000 ML of planned environmental water is also available for ecological and water quality use from the start of 2013-14.
Environmental watering aims for 2013-14
The Lachlan Riverine Working Group (LRWG) has considered the conditions of assets, water availability and climate forecasts and recommended that under the forecast ‘moderate’ resource assessment, the management outcomes for the water year are to maintain ecological health and resilience.
For this management outcome, NSW has nominated priority environmental watering actions for the 2013-14 water year. These include water delivery to the lower Lachlan River channel and wetlands, lower Willandra Creek and Lower Gum Swamp.
For further information contact Justen Simpson, Senior Team Leader, Environmental Water Governance, NSW Office of Environment and Heritage: phone: (02) 6229 7140.
Adaptive management of environmental water
The Lachlan is a long, regulated river system with highly variable flows. In dry years, no flows reach the end of the system. Many of the key wetlands are in the lower end of the catchment, on the extensive unregulated effluent creek system or the floodplain. Relatively high channel flows, or even overbank flows, are required to inundate the wetlands.
Environmental water holdings are managed in conjunction with other river flows to:
Annual Environmental Watering Plan 2013-14
The Lachlan Valley Annual Environmental Watering Plan 2013-14 (130580LachlanAEWP.pdf, 2.2MB) outlines the environmental water scenarios in detail.
Environmental Water Advisory Group
The Lachlan Riverine Working Group advises OEH on environmental water planning and delivery. It is chaired by the Lachlan Catchment Management Authority.
OEH manages environmental water in the Lachlan catchment in partnership with:
Environmental water planning is supported by the following key documents and plans:
Reports on environmental water use
Environmental water use for 2012-13 is reported in Environmental water use in NSW: Outcomes 2012-13.
Wetland and environmental watering projects and activities
On 8 June 2012, State Water started environmental water releases (translucent flows) from Wyangala Dam in accordance with the provisions of the Water Sharing Plan for the Lachlan River (WSP). These were the first translucent releases from Wyangala Dam since 2001 and continued through to late July 2012, with brief intervals, depending on the pattern of rain inflows to the dam and tributaries below the dam.
These releases have travelled down the river as a series of high-flow pulses. Translucent releases provide for a more natural flow regime within the river system by allowing some natural dam inflows to pass down the river for environmental benefit.
The hydrological and seasonal triggers established by the WSP ensure the key ecological riverine and floodplain features of the Lachlan River are targeted during translucent releases. This increases the positive outcomes for wetland flooding as well as waterbird and native fish breeding.
The translucent releases have led to rising river alerts for the Lachlan River and minor flood levels have been reached in areas downstream of Brewster Weir.
Page last updated: 13 March 2014