Predicting hydrologic responses to climate changes in highly glacierized and mountainous region Upper Indus Basin

The Upper Indus Basin (UIB) is a major source of supplying water to different areas because of snow and glaciers melt and is also enduring the regional impacts of global climate change. The expected changes in temperature, precipitation, and snowmelt could be reasons for further escalation of the problem. Therefore, estimation of hydrological processes is critical for UIB. The objectives of this paper were to estimate the impacts of climate change on water resources and future projection for surface water under different climatic scenarios using Soil and Water Assessment Tool (SWAT). The methodology includes: (i) development of SWAT model using land cover, soil and meteorological data; (ii) calibration of the model using daily flow data from 1978-1993; (iii) model validation for the time 1994-2003; (iv) bias correction of Regional Climate Model (v) utilization of bias corrected RCM for future assessment under RCP4.5 and RCP8.5 for mid (2041-2070) and late century (2071-2100). The results of the study revealed a strong correlation between simulated and observed flow with R2 and NSE equals 0.85 each for daily flow. For validation, R2 and NSE were found to be 0.84 and 0.80 respectively. Compared to baseline period (1976-2005), the result of RCM showed an increase in temperature ranging from 2.36°C to 3.50°C and 2.92°C to 5.23°C for RCP4.5 and RCP8.5 respectively, till the end of 21st century. Likewise, the increase in annual average precipitation is 2.4% to 2.5% and 6.0% to 4.6% (mid to late century) under RCP 4.5 and 8.5 respectively. The model simulation results for RCP4.5 showed increase in flow by 19.24% and 16.78% for mid and late century respectively. For RCP8.5, the increase in flow is 20.13% and 15.86% during mid and late century respectively. The model was more sensitive towards available moisture and snowmelt parameters. Thus, SWAT model could be used as effective tool for climate change valuation and for sustainable management of water resources in future