Climate change directly affects the water availability at local, regional and global scales. Land use is another factor that affects the hydrologic cycle of a catchment. Quantifying the probable impacts from the combined changes in climate and land use pattern is necessary for policy and decision making. Being the driest inhabited continent and having highly variable climate, Australian water resource is already in a stressed condition and future uncertainty is posing more risk. The main aim of this study was to assess the probable, individual and combined, impacts of climate and land use changes at a catchment scale. Within the iconic Murray-Darling Basin of Australia, two sub-catchments of the Murrumbidgee River were selected as study catchments. Physically based hydrological model Soil and Water Assessment Tool (SWAT) was developed for these two catchments. Four General Circulations Model outputs (CNRM-CM3, CSIRO-MK3.5, ECHam5 and MIROC3.2 for 2030, 2050 and 2090) and three scenarios (B1, A1B and A2) of IPCC were used as future climate scenarios. Several temperature rise (1 0C, 2 0C, 4 0C) and rainfall variation (-20 %, -10 %, -5%, +5 %, +10 % and +20 %) scenarios were also considered. Governmental planned future residential and agricultural development land use maps and several hypothetical land use change (5 % and 10 % pasture converted to forest and different location dependent land use changes) scenarios were used in the analysis. Residential and agricultural development scenarios were simulated with IPCC B1, A1B and A2 scenarios for all the three future time periods. Different temperature rise and rainfall change scenarios were analysed for 10 % pasture to forest conversion scenarios. Successful technical interpretation of the Australian data sources by developing SWAT database followed by sensitivity analysis, calibration and validation, resulted in an effective model of the study catchments. Monthly Nash Sutcliffe Efficiency (NSE) was found to be 0.786 and 0.846, respectively for calibration and validation periods of Yass River whereas the results obtained for Kyeamba Creek were 0.602 and 0.652, respectively. The results indicated that SWAT could be confidently used to study the hydrology and long term catchment level scenario analysis for the Australian condition. Curve number for moisture condition II (CN2) and soil evaporation compensation factor (ESCO) were found to be the most sensitive parameters for the study catchments. Streamflow was found to be highly sensitive to rainfall and temperature changes and sensitivities were nonlinear. Simulation results for Yass catchment indicated that 10 % increase in rainfall could increase streamflow by 44 % whereas 1 0C increase in temperature could reduce flow by 16 %. Although CN2 was found to be the most sensitive parameter, its sensitivity was found to be less than the rainfall sensitivity. Both catchments are likely to face small change in streamflow in the recent future for the combination of selected climate change scenarios. However, high reduction (44 % for Kyeamba Creek and 72 % for Yass River) in streamflow is expected at the end of this century. Summer and spring stremflow is expected to decrease for Yass River for all scenarios and time periods whereas moderate increase in flow is expected for winter and autumn flow of few scenarios. On the other hand, the summer flow showed an increasing pattern for Kyeamba Creek but spring flow is expected to decrease for all scenarios. The impact of land use change on streamflow was found to be low compared to rainfall and temperature changes. The location and elevation of land use changes were also found to affect streamflow generation. In general, land use changes in parts of the catchment far away from the outlet can cause higher streamflow reduction than similar changes near the outlet whereas a land use change at lower elevation causes higher streamflow reduction than similar land use change at higher elevations.
|Qualification||Doctor of Philosophy|
|Place of Publication||Australia|
|Publication status||Published - 2015|