Climate Change and Hydrology of a Snow-fed Watershed in Western Nepal

Many river basins across the globe are experiencing varying degrees of impacts from climate change. Snow-fed watersheds are expected to be affected even more. Chamelia, a tributary of Mahakali river basin, is a snow-fed river in the western Nepal with catchment area of 1,603 km2above the confluence with Mahakali River. Forest cover (40%) and rainfed agriculture (28%) covers more than two-third of the watershed. Topography varies from 505 to 7,090 m. According to the data from Department of Electricity Development (DoED) this watershed contains 14 licensed hydropower projects of varying capacities. Climate change may affect various aspects of the hydropower project, all of which are hinged around hydrology. This study simulated hydrological response of Chamelia watershed using Soil and Water Assessment Tool (SWAT) as an input for a hydro-economic model to analyze the water-energy-food nexus. The model was calibrated for the period of 2001-2007 and validated for 2008-2013 and then used to examine the streamflow response to climate change. Future climates for near-future (2020-2045), mid-future (2046-2070) and far-future (2071-2095) were considered based on CSIRO-CCAM Regional Circulation Model (RCM), derived from ACCESS1, downloaded from South Asia Cordex for RCP4.5 and RCP8.5 scenarios and then bias corrected using linear scaling method. Results, based on climate date at Station-103 showed that maximum temperature under RCP4.5 (RCP8.5) scenario for near-, mid-, and far-futures are projected to increase by 1.2°C (1.4°C), 1.5°C (2.8°C), and 2.3°C (2.6°C), respectively, from the baseline. Minimum temperature for the same scenarios and future periods, in the same order, are projected to increase by 1.1°C (1.5°C), 2.1°C (3.6°C), and 2.5°C (4.7°C), respectively, from the baseline. Precipitation in the other hand under RCP4.5 (RCP8.5) scenario for near-, mid-, and far-futures are projected to increase by 10.2% (10.4%), 7.6% (13.6%), and 3.1% (12.2%), respectively, from the baseline. As a result of the projected changes, streamflow is expected to alter at varying rates for the three future periods of time and two scenarios. The ultimate results of this nexus study are useful for water infrastructure planning to ensure long-term sustainability in the changing context.