IMPACT OF CLIMATE CHANGE ON SNOWMELT RUNOFF: A CASE STUDY OF TAMAKOSHI BASIN IN NEPAL

ABSTRACT: The Himalayas and glaciers are huge storage and very important source of fresh water. On the other hand, they are one of the most sensitive indicators of climate change as they grow and shrink in quick response to changing air temperature. Surface temperature of the earth is rising globally, which is the major indicator of global climate change. The global climate change has already greatly affected the world in many folds. The Himalayan ice and glaciers are gradually melting due to global temperature rise resulting to significant shrinkage in snow-covered area, retreating of glaciers at rate of tens of meters per year and formation of glacier lakes. These changes are greatly affecting runoff patterns and increasing the risks of Glacier Lake Outburst Flood (GLOF). Himalayan snow and glaciers are sources of many rivers in the regions and Tamakoshi River is one of them. This research aims to assess impact of the climate change on snowmelt runoff in Tamakoshi basin. It is located at above than 1960m altitude and more than 60 % area lies above 4000m. For simplicity, the Positive Degree Day (PDD) (temperature index) is used for snow and glacier melt estimation. Geographical Information System (GIS) is used for automatic delineation of watersheds from Digital Elevation Model (DEM) and ERDAS Imagine software is used to delineate the snow and glacier covered area of rugged and inaccessible terrain from processing of satellite images. Runoff pattern is analyzed using conceptual precipitation and snowmelt runoff modeling (SRM) tools in different climatic conditions (i.e. temperature). The results highlight considerable contribution of snowmelt and glaciers to runoff, and significant impact of climate change on snowmelt runoff