Impact of Climate Change on Snow melt in Marshyangdi River Basin of Nepal

Abstract

The climate change in general is the change in precipitation and temperature pattern which has potential impacts on economy, ecology and environment of Himalayas. Most of the studies of glacier melting and retreating are the main focus in Himalayas. Most of the study of glacier of Nepal shows that the glacier is undergoing rapid deglaciation. Snow and glacier melt contribution in Marshyangdi River have not been studied. Hence this study implemented the process-oriented distributed hydrological model J2000 model to investigate the contribution of snow and glacier melt in snow fed stream. The J2000 model able to distinguish between different runoff components including snow and glacier melt contribution. Hydrological modelling plays an important role in understanding hydrological process of a basin. The dynamically downscaled precipitation and temperature data were used for the future climate scenarios prediction for period of 2020-2050s, under the Representative Concentration Pathway’s scenarios RCP4.5 and RCP8.5 scenarios. The downscaled RCPs data was used to run the distributed hydrological J2000 to study the climate change impacts on snowmelt of Marshyangdi River basin. Increase temperature in future scenarios results the increase snowmelt contribution. The result of the model show there was total 20% contribution of snow melt to stream flow which will increase by 29% and 38% in RCP4.5 and RCP8.5 scenarios respectively which shows the shifting of snowline to higher altitude in future due to the increase temperature. The study shows that 5.4% increase of rain precipitation increases 14% of discharge in RCP4.5 scenario and 3.9% increase of rain precipitation increases 13% of discharge in RCP8.5 scenario. High snowmelt contribution in future scenarios increases the river discharge of study basin. The analysis shows the contribution of base flow will decrease whereas the overland flow will increase by 30% and 23% in RCP4.5 and RCP8.5 respectively. Actual evapotranspiration is highly affected by the climate change. The non-parametric Mann Kendall and Sen’s slope estimator for the trend analysis shows warming of the basin. And precipitation trend at northern part of basin is decreasing whereas the lower part of basin show increasing trend. With respect to the result of various runoff components, the overland flow RD1 will increase in future scenarios which conclude there will be increase of flood event in future.