Modelling the future use of reservoirs: A case study exploring the impact of operating rules and climate change

Abstract An 8800 km pipeline is currently being constructed in western Victoria to replace 17,500 km of open channel system. This Wimmera Mallee Pipeline Project (WMPP) will provide reticulated water to 36 towns and about 6000 farms across an area of approximately 2 million hectares. With this pipeline will come vastly improved efficiencies in the supply of water, with an estimated water saving of 103,000 ML being returned to the environment, existing consumptive use, new development and for recreation. The main source of supply to the WMPP will be from the headworks system located in and around the Grampians National Park, with the northern (Mallee) area supplied direct from the River Murray. The Grampians headworks system consists of 11 storages, each with their own unique hydrologic, environmental and socioeconomic attributes. The number of storages and their range of attributes enable a degree of flexibility with regards to the future configuration and operation of the headworks systems to meet the various demands of urban, domestic and stock, irrigation, recreation, new development, intensive industry, and water for the environment. This paper presents some of the modelling work undertaken, using the REALM modelling software package, to explore the effects that different system configurations, operating rules and climate change scenarios have on the ability of the headworks system to meet the requirements of basic water supply, environmental needs and community expectations. Results are presented in the form of a case study, outlining the changes in the total system water balance post-WMPP, changes in users’ security of supply, and exceedance plots for total system environmental outflows and total system storage.