Forest vegetation monitoring and runoff in water supply catchments affected by drying climate

The south-west of Western Australia has experienced reduced rainfall over recent decades. Annual rainfall in the state´s capital city, Perth, has declined by approximately 20% since the 1970´s. Runoff from the forested catchments into the city´s water supply dams has declined more dramatically - of the order of 50%. Forest vegetation plays a major role in catchment water balance. Thinning of forest cover has been proposed as a means to increase catchment yields, and a trial is being conducted. Time series Landsat imagery provides information on historic forest disturbance on all catchments and an alternative data integration analysis combining these indicators with historical rainfall and runoff data is being conducted to estimate effects of forest thinning on catchment runoff under different rainfall scenarios. The remote sensing analysis has provided indication of forest adaption to the drying climate. These results and a sample of the hydrological data and analysis are presented in this paper.