Environmental flows
The Sydney Catchment Authority (SCA) recognises that its dams and reservoirs affect the natural flow of water downstream. The SCA provides water to downstream rivers through environmental flows - water released from the storages to help restore ecological processes and biodiversity of water dependent ecosystems. The environmental flows represent around two to three percent of the total water we use each day.
Current environmental flows
Warragamba system
The SCA currently releases 33.3 million litres per day from Warragamba Dam into the Nepean River for environmental purposes. The NSW Government will consider increases to these interim releases and set a new regime of releases by 2015.
Shoalhaven system
The SCA releases water from Tallowa, Wingecarribee and Fitzroy Falls reservoirs to help improve the environmental health of the rivers downstream and sustain riparian rights. At Wingecarribee, at least three million litres of water is sent downstream every day for environmental purposes. Environmental flow releases from Tallowa Dam are linked to natural inflow volumes, up to 90 million litres daily. New environmental flows have been announced by the NSW Government to better mimic natural inflows into the dam.
New infrastructure works are currently underway at Tallowa Dam to allow the new variable environmental flows. The SCA is also installing a fish 'lift' to allow native fish to move in upstream and downstream The new flows and the fish lift will improve the overall health of the river.
At Fitzroy Falls Reservoir, environmental release levels are linked to inflow rates measured at Wildes Meadow Creek.
Upper Nepean system
The SCA releases water daily from the Upper Nepean dams and weirs for environmental purposes, including at least 4.4 million litres from Nepean Dam, 1.9 million litres from Cordeaux Dam, and 1.3 million litres from Cataract Dam. Downstream of the Upper Nepean dams, at least 10.5 million litres is released daily from Pheasants Nest Weir and 1.7 million litres at Broughtons Pass Weir. New environmental flow releases from Avon Dam in the Southern Highlands began in March 2008. New environmental releases from the other dams and weirs will start in 2010 when new outlet works are completed.
Woronora system
The SCA modified Woronora Dam's outlets in 2002 to enable environmental releases, linked to inflows. This helps conserve the river's ecological systems and biodiversity of water dependent species.
Blue Mountains system
The Blue Mountains system is comprised of a six small reservoirs located high in the catchment. Apart from overflows during periods of high rainfall, there are no current environmental releases from these dams.
