Environmental water in a regulated river system: the Murrumbidgee River planning approach to the determination of environmental needs.

The major platform of the Council of Australian Governments (COAG) water reform program is the equitable and sustainable sharing of surface and groundwater resources between the environment and consumptive water users. In the regulated section of the Murrumbidgee River below Burrinjuck Dam, approximately 2,800 GL of the available surface water (4,300 GL) is diverted or extracted for irrigation uses in the Murrumbidgee Irrigation Area and Districts, and in the Coleambally Irrigation Area. Environmental flow rules have been developed for the Murrumbidgee which provide for an allocation of water to the environment but on the basis of no more than a 10% impact on farm-gate income of irrigation farmers. This provision limits the volume of water that can be used for environmental purposes, so the most effective use must be made of it. To identify and quantify the benefits to the environment of this limited additional volume of water and to determine the most effective use of the water, an "environmental spreadsheet matrix" has been developed. This paper outlines the development and use of the matrix in the planned implementation of flow regimes appropriate to the protection and enhancement of riparian and aquatic ecosystems and ecological processes.