Impact of Climate Change on River Flow and Hydropower Production in Kulekhani Hydropower Project of Nepal

This study aims to quantify changes in discharge in the rivers of the Kulekhani watershed due to climate change and examine its future impact on power generation from the Kulekhani Hydropower project. The future climate conditions of the watershed are predicted by downscaling the outputs of A2 and B2 scenarios of the HadCM3 global circulation model for three time periods: 2010 2039, 2040 2069 and 2070 2099 (2020s, 2050s, and 2080s, respectively). The major change in temperature is predicted for 2080s for the A2 scenario, as the maximum and minimum temperatures are predicted to be increased by 1.5 degrees C and 2.8 degrees C, respectively. However, the average precipitation of the watershed is expected to decrease in all future time periods. HEC-HMS hydrological model is used to simulate the river discharges during baseline and future periods in the watershed. A decrease in discharge during the wet months (May to September) and an increase during the dry months (October to April) is projected in future time periods against the baseline period for both scenarios. Reservoir simulation is performed using HEC-ResSim in order to analyze the future change in power generation for different operating time settings. Assuming that the hydropower plant operates for 7 h/day during the baseline period (1982-2009), the average power production is expected to decrease by at least 30 % for both A2 and B2 scenarios in the future. Least reduction in power generation (8-13 %), against the baseline period, is observed when the reservoir is operated for 10 h/day in the dry months and 3 h/day in the wet months. The study provides information regarding the climate change impact on Kulekhani hydropower and will assist in planning new hydropower projects.