Affiliations: [a] Himalayan Cryosphere, Climate and Disaster Research Center, Department of Environmental Science and Engineering, School of Science, Kathmandu University, Dhulikhel, P.O. Box 6250, Kathmandu, Nepal | [b] International Centre for Integrated Mountain Development, Lalitpur, P.O. Box 3226, Kathmandu, Nepal
Abstract: With a paucity of glacio-hydrological data, the temperature index model often serves as a powerful tool in melt modeling on a basin scale. This study uses a positive degree-day factor to estimate snow and ice melt and then daily discharge of the Sangda River basin located in Mustang district, western Nepal. The basin encompasses 438 km2 with ~12% glacierized area. The model, calibrated for 2012 and validated in 2013, simulates daily discharge efficiently when compared with the observed discharge. The Nash-Sutcliffe Efficiency (NSE) for calibration and validation years are 0.91 and 0.92 and volume difference are ~5% and ~7%, respectively. The relative contribution of snow and ice melt to the discharge in 2012 is ~19% and in 2013 is ~16%. The bias corrected temperature and precipitation data are forced in the model to generate future discharge of the basin for CMIP5 RCP4.5 and RCP8.5 scenarios. Between 2015 and 2050, the average discharge in the basin is 7.52 m3/s and 7.57 m3/s for RCP4.5 and RCP8.5 scenarios, respectively. The projected discharge is predicted to be highest during 2021-2030, whereas glacier melt is highest during 2041-2050 for both scenarios. The sensitivity tests reveal that a warm and dry climate generates more discharge than a wet and cool climate. These results from this study provide a general basis for water planners and policy makers to improve management of water resources in this region for present and future uses.
Keywords: Temperature-index model, Snow and ice melt, River discharge, RCP4.5 and RCP8.5