The Impact of Climate Change on Runoff Generation in Langtang Basin Nepal

Abstract

Climate change has potential impacts on economy, ecology, and environment of Himalayas.Climate change studies in Himalayan regions have focused mainly on glacier melting and retreating, Glacial Lake Outburst Flood (GLOF) etc. Changing temperature has direct impacts on glaciers and snow that affects the snow melt and river discharge.Hence, this research has been carried out to understand the impact of climate change on runoff generation of Langtang basin.This runoff is important for planners and designers in the aspect of irrigation, hydropower,and drinking water supply and so on.So, the runoff estimation study is essential.This study is carried out using monthly Thornthwaite water balance model.Thornthwaite monthly water balance model is one of the popular model developed by USGS for the runoff estimation and can be applied to estimate the runoff of snow and glacier bound catchment. This study also focuses on the runoff estimation of past, present and future scenario at Langtang region of Nepal by using the Thornthwaite model.The outputs of the analysis on temperature trend revealed a fasterwarming trend in Langtang area (i.e. 0.084 ºC/year).The mean annual soil moisture storage is increasing pattern (i.e.0.71mm/year).The precipitation and runoff are also observed increasing (i.e.10.59mm/year and0.8mm/year).The coefficient of determination of calibration and validation are 0.926and 0.996 that implies that the model is well validated and calibrated as well.The increase/decrease in temperature and runoff has proportional relationship and increase/decrease in rainfall and runoff has also proportional relationship.The projected runoff by the model is slightly decreasing from 2001 to 2060 this result shows that the chances offlood in summer and possible droughtin winter may further enhanced in the future.The main outputs of this study help to implement appropriate strategy for water resources management and hydropower development and provide a strong message on the scenario of the Global impact of warming in the Himalayan region.