Determining environmental flow needs and scenarios for the River Murray System, Australia

AbstractThe River Murray is a “working river” in the sense that its regulation and management delivers significant economic wealth and social benefits to local communities and wider Australia. Recognition of ongoing deterioration of the riverine environment has prompted several environmental flow initiatives, including establishment in 1999 of the “Environmental Flows and Water Quality Objectives for the River Murray Project” (the Project). This paper reports progress on the main aspects of the Project to date.A review of the impacts of flow regulation on the health of the River Murray revealed evidence for decline, but in many instances the case for flow regulation as the sole or main cause is circumstantial or uncertain. A Basin-wide snapshot study of stream condition found evidence for extensive degradation, with disturbance to the catchment and changes to nutrient and suspended sediment loads being the greatest contributors. It is apparent that the rivers and streams of the Basin are beset by multiple impacts, with flow regulation being the main problem in the River Murray System. The Project addresses this recognised main cause of degradation in the River Murray System. A profiling survey demonstrated that whilst there was unequivocal support for the principle of an environmental allocation, stakeholders were not supportive of a process that excluded them from involvement in decision making. Thus, establishment of an inclusive project organisational structure has proved to be critical, and will continue to be critical, to obtaining information and support across different States, and from a range of stakeholder groups.Environmental flow needs of the River Murray were based upon the findings of two earlier Scientific Panel studies. Another Expert Reference Panel, established specifically for the Project, adopted a risked-based approach to assessment of environmental flow options. Environmental flows can be delivered by making more water available, by altering the distribution offlows (operational changes) or by altering flow regulating structures (structural changes), or through some combination of these. Flow scenarios under development for consideration by the Ministerial Council in 2002 are being devised on this basis. It is recognised that recovering water from existing water users would likely involve significant social, economic, political and practical challenges. Ongoing work to investigate and resolve these aspects of the Project is being undertaken with the same level of rigour as applied to the development offlow scenarios. Although the Project is in a relatively early stage of development, for the first time, an overall sense of the scale of what is required to achieve significant environmental outcomes in Australia’s largest and most high profile river system has been realised. section measurement is obtained. Presented in this paper is an outline of an alternative method Also presented in the paper is a discussion of its application for the gauging of rapidly varying discharges in streams within an urban drainage system. Additional informationNotes on contributorsChristopher J GippelChris Gippel is a potamologist with a BSc (Hons) from the University of Newcastle and PhD from the University of NSW. After a long research career at several universities, Chris now runs a private consulting firm that provides specialist services to the water industry in the areas of geomorphology, hydrology, river rehabilitation and environmental flows. He continues to innovate and lead development of ideas and technologies in these fields within the consulting environment. Chris has published widely, and in 1992 was recipient of an Australian Bicentennial Fellowship. He can be contacted at fluvials@hotmail.com.Tony McLeodTony McLeod BE(Hons) PhD (Melbourne) is a member of the Environmental Flows team at the Murray-Darling Basin Commission. Since joining the MDBC in 1998 he has been involved in the implementation of the Cap on diversions throughout the Basin, operation of the River Murray System and environmental flows. His interests are water sharing between environmental and consumptive needs and management of trans-boundary water resources.