Rainfall Characteristics over the Northwest Himalayan Region

Abstract

The Northwest Himalayan (NWH) region constitutes a unique geographical setting with a complex interaction between atmosphere and topography. The region is also the birthplace of many perennial rivers like the Ganges, Yamuna, Indus, Chenab, etc. and their various tributaries. The precipitation processes in the region dominate not only the geomorphological processes and terrestrial hydrological cycle but are also highly relied upon for food and water availability, thus, playing a decisive role in the socio-economic survival of millions of people inhabiting the basins of these rivers. The precipitation pattern in this region is mainly controlled by two major atmospheric circulations: Indian summer monsoon (ISM) lasting from June to September and Western disturbances during the winter season from December to March. While the Eastern Himalayan ranges receive precipitation mainly through monsoon rains, the NWH receives both rainfall (liquid) and snow (solid) in summer and winter season, respectively. The monsoon rains contribute roughly 75–80% to the annual precipitation of the NWH and closely control the river discharge in the basins.