Impacts of land use and climate change on streamflow and water balance of two sub-catchments of the Murrumbidgee River in south eastern Australia

This study estimates the probable impacts of land use change in combination with climate change on the streamflow of two sub-catchments of the Murrumbidgee River; Yass and Kyeamba in south eastern Australia. A physically based hydrological model Soil and Water Assessment Tool (SWAT) in combination with three IPCC scenarios, four General Circulation Models (GCM) downscaled outputs and two governmental proposed future residential and agricultural land development plans were used for predicting the impact on streamflow and water balance components. Sensitivity of streamflow and water balance components to land use and climate changes were also assessed. The impact of land use change was found to be lower than that of rainfall and temperature. A 10 % decrease in rainfall caused 18 % reduction in flow whereas 10 % pasture to forest conversion reduced flow by only 1.5 % for Yass catchment. The impact of the change was different for the two catchments. 1 oC rise in temperature can cause 16 % flow reduction for Yass catchment but the reduction is only 1.7 % for similar temperature rise in Kyeamba catchment. The impact of land use change on streamflow and water balance components was also found to be dependent on the location and elevation of the land use. When the individual water balance components were considered, surface flow was found to be highly sensitive to land use change in both the catchments while groundwater flow was found to be sensitive for the Yass catchment and lateral flow for the Kyeamba catchment.