Assessment of water resources availability in Krishna upper basin of India with SWAT model using CORDEX climate projections

The impact of climate change on water balance components needs to be quantified from regional to local scale to manage water resources and suggest adaptation strategies to cope with future challenges. The present study was carried out to understand the climate change impact on water resources available at Krishna upper basin of India. CNRM RCM model was used to simulate the projections of rainfall and temperature with two RCP scenarios RCP 4.5 and RCP 8.5 and three time periods 2020-40 (near century), 2041-70 (mid-century) and 2071-99 (end century). It was observed that the change in mean annual rainfall projected by CNRM model under RCP 4.5 during 2020-40, 2041-70 and 2071-99 were 11.7, 26.7 and 32.2%, respectively and 18.6, 34.5 and 41.5%, respectively under RCP 8.5 scenarios. The CNRM model under RCP 4.5 scenario projected an increase in annual mean temperature for the period 2020-2040, 2041-2070 and 2071-2099 by 0.65, 1.06 and 1.49°C, respectively and 0.72, 1.55 and 2.41°C, under RCP 8.5 respectively. The SWAT model simulated that the projected annual surface runoff is likely to increase by 18, 70.2 and 102.7% under RCP 4.5 and 159.3, 106.9 and 66.2% under RCP 8.5 scenario during the future time slices of 2020-40, 2041-70 and 2071-99, respectively with reference to baseline period (1961-90) of surface runoff 195 mm under CNRM model. The annual surface runoff during the future periods is found to increase by 19.0, 50.0 and 27.0% under RCP 4.5 and 43.1, 100.5, 55.6% under RCP 8.5 scenario during 2020-40, 2041-70 and 2071-99 periods. It is concluded that the rainfall during the monsoon months except for September may increase in future periods and water availability in all the sub basins is expected to increase in future periods.