Review of the 1999 ACT Environmental Flow Guidelines: A report by the CRCFE to Environment ACT

1) This is an ecological review of the 'ACT Government Environmental Flow Guidelines' (1999) (or EFG). The EFG are a statutory document that establishes the water requirements in streams and lakes in the ACT, to ensure aquatic ecosystems are sustained. The CRC for Freshwater Ecology has been asked to provide advice on the efficacy of the EFG, and on improvements that can be made in the general approaches and actual flow rules for sustaining ecological values. 2) The approach taken in the review is to assess the effectiveness of prescribed environmental flows by reference to monitoring data and research on rivers within the ACT, and by consulting with local scientific experts. Advice is provided on the retention of current flow practices, or their modification to better achieve ecological objectives. This information could contribute to adaptive management in the near term, or to a more systematic formulation of environmental flow guidelines, should that be undertaken in the future. Performance of the environmental flow guidelines 3) The performance of environmental flows needs to be considered in reference to objectives that reflect catchment uses as well as river condition. The approach taken in this review is to judge sustainability in reference to established 'performance criteria' where they exist. 4) In regulated parts of the Cotter River system the current EFG low-flow levels (supplemented by unmanaged reservoir spills and inflows), are delivering many desirable ecological benefits. General river condition is at or above levels specified in performance criteria, and appears to have improved since the implementation of the EFG, despite the drought and fires. Both Macquarie Perch and Two-spined Blackfish have successfully spawned during the drought. 5) Adaptive management principles embedded in the EFG, and further developed in practice, worked well in the Cotter River during 2003/04 in relation to setting environmental flows during drought and under a demonstrated needs scenario, as well as in relation to capturing new information. 6) In the Queanbeyan River downstream of Googong Dam the current EFG are maintaining conditions at or above performance criteria levels. 7) The monitoring data are insufficient to determine the ecological value of environmental flows in other systems. Advice on retention of or changes to guidelines 8) A process of setting clear ecological objectives could be considered for all river types and reaches within the managed area. The process could target CRC for Freshwater Ecology ACT e-flow guidelines review systems with tailored environmental flows, and could involve focused monitoring to allow assessment of performance against the objectives. 9) This review provides draft ecological objectives, arising from a workshop held as part of the review. The review also proposes environmental flows that should achieve the objectives, or that can be trialled. 10) Some suggestions are made for changes to existing environmental flows, including introducing flow variability in releases from the dams, major refinements to flushing flows, and a reduction in the flow required for fish spawning in the Cotter River. 11) Continued integration of environmental flow management, monitoring and assessment, within an adaptive management framework, will lead to ongoing benefits. Consideration should be given to having clearer formalisation of an active adaptive management strategy in the EFG. 12) Monitoring of the effectiveness of environmental flows to areas beyond the water supply reaches should be considered