The management of Lake Burragorang in a changing climate: The application of the Index of Sustainable Functionality

Lake Burragorang is the largest water supply source for the Sydney region, providing up to 80% of Sydney's water supply. The Index of Sustainable Functionality (ISF) was applied to the geographical domain of its catchment (Warragamba Catchment) for the 20 year period from 1989 to 2008 as a measure of its health and sustainability. The ISF values showed a slight negative trend over the study period, indicating decreasing functionality of the reservoir; however, climate variability, especially its effect in significantly decreasing the lake water level, played a dominant role. The effect of water level on the occurrence of an algal bloom event in 2007 was investigated using the Estuary, Lake and Coastal Ocean Model coupled with the Computational Aquatic Ecosystem Dynamics Model (ELCOM-CAEDYM) simulations. Results reinforced the dominant role played by water level, demonstrating that at a higher water level (an increase of 20 m) the bloom may not have occurred. Increased alertness and more rapid response to prevent events such as algal blooms could be achieved through the use of ELCOM-CAEDYM combined with the ISF.