Climate Change Investigation of Swat River using HEC HMS hydrological Model

Abstract

Pakistan is included in the most water stressed countries in the world and its water resources are vulnerably affected by the climate change. Monitoring regional watershed can help to secure resources for upcoming future. Our research based on understanding hydro- climatic regime of Swat River basin up to Khawaza Khela using physical based HEC-HMS model. Model was calibrated and validated on daily scale and evaluate using statistical performance indicator, it was able to provide acceptable performance range. Nash-Sutcliff coefficient (Ns) is found as 0.84 and 0.81 for calibration and validation, respectively. Root mean square error (RMSE) results 5.5 and 2.8 for calibration and validation respectively. The coefficient of determination R2 is 0.86 and 0.84 for calibration and validation respectively. Further for climate change two scenarios were selected RCP4.5 and RCP8.5 of MIROC5 model. Climate variables of both scenarios were linearly bias corrected and incorporated into the model for future run. Future analysis of precipitation showed increase in precipitation for both RCPs. At the end of century total annual rise of +195mm (14.8%) was observed for RCP8.5 and 119mm (9%) was observed for RCP4.5. On seasonal basis winter precipitation seems to grow over the century, other seasons remain somewhat random. Analysis of river flow seems to predict higher magnitudes of flow. At the end of century, RCP4.5 suggest 38.9% increase in flows and RCP8.5 showed 40.9% increase in flow. Seasonal analysis reveals that highest positive deviations were recorded during the season of Monsoon and Autumns for stream flow.