Water Management
Hawkesbury-Nepean environmental flows and weirs project
Healthy rivers and catchments are important for the ecosystems, communities and economies that rely on them. Dams and weirs affect the natural flow of water in rivers, affect water quality, restrict the migration of fish through the river and limit their habitat.
An environmental flow is water released from a dam or weir for the health of the river downstream. Environmental flows are important to improve water quality, fish passage and habitat conditions for native flora and fauna. They help native fish to breed, reduce the growth of weeds and improve water quality for recreation.
The NSW Government's commitment to improving the health of the Hawkesbury-Nepean River is documented in the NSW Metropolitan Water Plan 2006. The Plan recognises the need to improve environmental flows and make better provision for fish passage in the Nepean River.
The new and variable environmental flow from the water supply dams and weirs in the upper Nepean River will mimic natural conditions as closely as possible. This will contribute to reducing the adverse effects that dams and weirs have on river health and ecological values.
The new environmental flows from all the Upper Nepean dams are to commence from the beginning of 2010.
Works at water supply dams and weirs in the Upper Nepean catchment
The Upper Nepean catchment consists of four water supply dams: Avon, Cataract, Cordeaux and Nepean and two major water supply weirs: Broughtons Pass and Pheasants Nest.
In order to release the environmental flows for the Nepean River, particularly when the water supply dams and weirs are not spilling, works are taking place at the dams and the water supply weirs. At Avon Dam new environmental release outlets have been installed, and new environmental releases started from Avon Dam in March 2008. Work has commenced on the other dams and supply weirs.
Works at weirs on the Nepean River
The Nepean River also contains a number of weirs from Maldon, south-west of Sydney, to Penrith. These weirs can act as barriers to the environmental flows and fish passage along the river. To make sure the environmental flows can make it all the way downstream, modifications are being made to most of these weirs. These works include the installation of environmental release outlets and the construction of new fishways.
The modifications will ensure that the weirs will continue to provide water for local irrigation, while also allowing the environmental flows and fish to move through the Nepean River.
During the works it is anticipated there will be no change to water levels at the weir pools, however there will be limited access to the weirs. A schedule of the works will be posted on this website when it is available.
Timeframe
Works will be undertaken at the:
- water supply dams from January 2009 to August 2009
- water supply weirs from February 2009 to September 2009
- weirs on the Nepean River from March 2009 to December 2009.
Further information
The following publications provide more detail on these activities:
- Hawkesbury-Nepean Environmental Flows and Weirs Project – Information sheet (PDF 93KB)
- Map of weirs on Nepean River (PDF 398KB)
- Media release – Announcing the works on the Nepean River weirs (PDF 50KB).
For further queries in relation to these works, and/or to keep updated about the proposed works, please contact nepeanriver@sca.nsw.gov.au.