Impacts of changes in climate on mountain water resources of Himachal Pradesh

The study examined the impacts of climate change on water resources, viz., surplus / deficit water balance, snowfall trends and surface water flow of major rivers of Himachal Pradesh. The analysis on surplus water balance clearly showed decreasing trends in all the agro-climatic zones during past three decades. Maximum availability of surplus water balance period showed a shift during July to August and registered a decrease of 35.7 percent. The low hill regions exhibited water surplus during kharif season and water deficit during rabi season, while, mid hill regions exhibited water deficit during kharif season and water surplus during rabi season during past three decades. The Mann-Kendall trend test of snowfall indicated a decrease in monthly average snowfall from September to December. The trend analysis further showed increasing trends of snowfall during January and February indicating delay in snowfall during winters. The decreasing trends of snowfall were observed during September to December and March to May indicating shrinking winter period. The significant decreasing trend of snowfall was observed during December and May. The trend test revealed significant decrease of surface water flow of river Beas at Manali and Parvati at Aut in Kullu district during all the months. The water flow of river Sutlej at Songtong in Kinnaur district also showed significant decreasing trends during winter months. Similarly, the annual water inflow of the Sutlej River at Bhakhra Dam showed decreasing trend also. Thus, the studies clearly indicated that water resources have been impacted due to changes in climatic conditions in mountains of Himachal Pradesh during past three decades.