Sydney

The Sydney Catchment Authority (SCA) manages banked environmental flow in the Sydney region.

Between 1 June 2005 and 3 March 2008, environmental flow releases into the Hawkesbury–Nepean River required under the SCA’s water management licence were halved as directed by the minister responsible for water in New South Wales due to the continuing drought. A condition of halving the flows was that the SCA would maintain a rolling 12-month bank in storage reservoirs and release the banked water as directed by the minister. The total banked water was 12,245 ML at the beginning of 2009–10.

The minister authorised that part of this banked water could be used to provide a high environmental flow release from Woronora Reservoir in February 2010. This event used 2,450 ML (see Line item 14.7.9.7), leaving a balance of 9,795 ML as applicable at the end of 2009–10.

Data source

• SCA and NSW Office of Water agreement.
• SCA database of daily requirements and releases.
• SCA compliance reporting to the NSW Office of Water.

Data provider

The Sydney Catchment Authority.

Method

For 2009–10, the released banked environmental flow volume was derived from valve-rating tables and stream gauging downstream of high environmental flow release from Woronora Reservoir. The banked environmental flow was reduced by the released volume.

Uncertainty

The reduction in the banked volume is based on measured data. Estimated uncertainty based on accuracy of stream gauging is +/–10%.

Approximations, assumptions, caveats/limitations

Nil.