Water demand and supply analysis under changing climatic conditions

Abstract

In this thesis, the Blue Mountains region and the Blue Mountains Water Supply System in western Sydney, New South Wales, Australia were selected as the study area and water supply system, respectively. In this research, impact of climate change on future water demand has been investigated by using the climate projections from a GCM and uncertainties in demand projections being estimated by developing a long term probabilistic water demand forecasting model considering stochastic nature of the predictor variables and correlation structures. The probabilistic water demand forecasting model has been developed by adopting a Monte Carlo simulation technique with multivariate normal distribution. Climate change impact on future catchment water yield (i.e. runoff) and their associated uncertainties are estimated by coupling the GCMs' projections with the rainfall-runoff models. Four different GCMs (MIROC, ECHAM 5, CSIRO Mk. 3 and CCCMA) and two rainfall-runoff models (AWBM and SIMHYD) have been used to estimate future catchment water yield scenarios. This research has also developed an integrated methodology to examine the performance of a water supply system under future climate, water demand and runoff scenarios in the future periods. It has been found that the impacts of potential future climate change on water demand are negligible. On the other hand, it has been found that future catchment runoff/water yield scenarios will be notably affected by the climate change conditions. Moreover, it has been found that consideration of future climate change scenarios on water demand and catchment yield in an integrated modelling framework can provide important insights on the reliability and resilience of a water supply system i.e. when a water supply system may not be able to provide the desired water supply. Furthermore, it has been found that the choice of GCM is the largest source of uncertainty in the forecasted runoff among other possible sources. The uncertainty due to the internal variability of a GCM (i.e. realisation uncertainty) has also been found to be notably high. The ranking of various sources of uncertainties are found to be as: GCM uncertainty > realisation uncertainty > rainfall - runoff model uncertainty > rainfall-runoff model parameter uncertainty. From this study, the main recommendation for water authorities/policy makers is to consider a number of possible estimates of future water demand and water yield scenarios in investigating the performance of a water supply system under changing climate regime. Consequently, a number of potential assessment scenarios, GCMs and rainfall-runoff models and associated uncertainties should be considered in estimating the future water demand and water yield scenarios. The developed methods along with the outcomes of the research would provide vital knowledge about the possible climate change impact on future water demand and runoff, and future performance of a water supply system for better planning and management of a water supply system. This will also help to develop appropriate adaptive strategies to supply adequate water to the communities. The methodologies developed in this thesis can be adopted to other regions and to other water supply systems in Australia and elsewhere in the world.

Date of Award	2014
Original language	English