Study of climate change impact in Himalayan Water Resource: a case study of Nepal

Abstract:

Himalayan region are regarded as water tower of Asia and has also covered high attention due to climate change owing to its glaciers melting. Water from those glaciers-fed basins are mostly utilized for hydropower, irrigation and drinking water supply to around 1.4 billion population downstream. The basin system, particularly in Nepal, is divided into three categories: (i) snow and glaciers fed: Koshi, Gandaki, Karnali and Mahakali basins (ii) from Mahabharat range: Babai, West Rapti, Bagmati, Kamala, Karnali, Mechi and (iii) Streams and rivulets from Chure hills: Surahinala, Badganga, Mohana etc. This study shows majority of flow (~78% of average flow) is from first category, 9% from second and 13% from third category. In the recent decades, especially during the dry season, rivers from third category have low runoff (or even zero)which leads to lack of water for irrigation and drinking water supply by lowering its water table.Interestingly, during monsoon season the whole region is facing high risks of flash floods and landslides due to unpredictable rainfall pattern. Increasing temperature trend (0.08˚Ca^-1) and weakening precipitation rate (7.9±1.2 mm a^-1) for last four decades shows indirect sign of climate change, though long time series in-situ observations are largely lacking in Nepal Himalaya. Our study supports high impact of climate change on potential generation of hydropower in Nepal which are more pronounced in coming decades.