Assessment of the Impact of Projected Climate Change on Streamflow and Groundwater Recharge in a River Basin

Abstract

In this work, a general approach for evaluating the impacts of projected climate change on streamflow and groundwater recharge in a river basin located in the humid tropical zone of India is presented. The projections of a GCM for two important climate variables, viz. rainfall and temperature for two scenarios, A2 and B2, are downscaled by a RCM to predict future climate in the river basin and then input into a physically based hydrologic model, SWAT, to evaluate the impact of projected climate change on streamflow in the river basin. Also, a simple conceptual semi-distributed model to assess the impact of projected climate change on direct groundwater recharge is developed and used to predict groundwater recharge in the A2 and B2 scenarios. This model is based on the water balance concept, linking the atmospheric and hydrogeologic parameters to different hydrological processes and estimates daily water table fluctuations. Results show that in the A2 scenario, for the southwest monsoon period, there is an average increase in temperature of 2 °C and a decrease in rainfall of 11.50 %. Predictions by SWAT indicate an increase in potential evapotranspiration of 1.14 % and a decrease in streamflow of 7.53 % from present-day average values. For the same period, in the B2 scenario, there is an average increase in temperature of 1 °C and a decrease in rainfall of 8.79 %. SWAT predictions show an increase in potential evapotranspiration of 1.12 % and a decrease in streamflow of 4.62 %. Similar trends are predicted for the north-east monsoon period also. Groundwater recharge is predicted to decrease by 7 and 4 % in the A2 and B2 scenarios, respectively.