Climate change impact assessment on water resources in the Blue Mountains, Australia

Climate changes, especially its impacts on temperature, precipitation and evaporation, have large effects on water resources. In recent years, water authorities in Australia imposed various water demand management strategies including mandatory water restriction to reduce water demand as the dam storage levels dropped quite low due to the prolonged droughts which affected the country for about 7 years in early 2000s. Since climate change can affect the water resources in many different ways, it is necessary to assess the potential impact of this change on water resources in a reservoir system for effective planning and operation of the reservoir system which are used for urban water supply. This study investigates the climate change impact on future runoff in Katoomba Catchment of the Blue Mountains regions, New South Wales, Australia. Three future climatic scenarios B1 (low), A1B (medium) and A2 (high) have been used in this study to run the model. Downscaled daily rainfall and evaporation data from CSIRO Mk 3 Global Climate Model have been taken as inputs into a continuous rainfall-runoff model namely Australian Water Balance Model (AWBM) to generate runoff sequences under future climatic scenarios. The calibration and verification results indicate that the model performances are quite good (NSE = 0.989; RMSE = 0.48; PBIAS = 4.57%) and it can be used to estimate future runoff for climate change impact studies. The prediction results by the AWBM show that the future runoffs can change by ± 80% under different climatic scenarios during the projection periods (2025-2040) in comparison to the base average annual runoff for the period of 2005-2010.