Impacts of Climate Change on climate variables and catchment stream-flow, using HBV model under BCM2 Scenarios

Climate change has led to change in climate variables of catchments and has impacts on surface water resources which could create crisis in water resources management. In this study, the impact of climate change was assessed on surface water resources of Bashar river catchment, located in Kohgiloye-o-Boir-Ahmad province. Future B1, A1B, and B2 scenarios of BCM2.0 model were downscaled via Change Factor method. HBV model is calibrated and validated for the catchment. Series of observed climate variables and future scenarios were put into HBV model and daily stream-flow series for both, historic and future (2067-2093) periods, were simulated. By comparing simulated discharges for historic and future periods, the climate change impacts are assessed. Results show that temperature and evapo-transpiration would increase in all of the months in future. Also precipitation and stream-flow would decrease through most of the months in 2067-93 period. Mean precipitation and mean discharge would decrease up to 40 and 50 percent respectively. Annual daily minimum discharges would obviously. For instance, Q95% via return period of 2 and 25 years would reduce up to 51%and 66%, respectively. Therefore, putting expedient measures to encounter changes in future climate is necessary, specially measures related to water resource management.