5-Recent Trends in Himalayan Hydrology.

Abstract

Snow and glaciers contribute substantially to the perennial water resource of Himalayan river basins. Systematic studies on snow precipitation, seasonal snow cover and glaciers in India have been undertaken only in the last three decades. The Himalaya are the largest storehouse off resh water and sources of mighty rivers such as Indus, Ganga and Brahmaputra. The mean annual rainfall over Himalayan region varies from 50 to 250 cm with lesser rainfall occurring around the foot hills of Himalaya. The mountainous area covered by snow is about 80% of the total area of Himalaya. The snowmelt runoff problem is complex, involving the interaction of many aspects of the watershed system. To analyse such complexity, it is necessary to represent the various aspects of behaviour of watershed in a computer model. Much research effort has gone into developing snowmelt models over the years. Glaciers are essentially reservoirs of both liquid and solid precipitation retaining winter snow and releasing it gradually. For proper management of high mountain water resources, it is necessary to known the amount and location of water stored in a frozen form, the pastern of its release due to melting and how the melt rates are affected by short term weather changes and long term climatic changes. Information of hydrological and meteorological parameters, especially, from altitudes above 3000 m is essential for a realistic assessment of water resources from snow and glaciers. During the last fifteen years techniques for application of remoter sensing to hydrology in general and snow and glaciers in particular have been developed and perfected in the country. A number of isotope techniques areal so in use for the study of snow and ice. A long-term perspective programme for glaciological studies in the countries of the region has to be evolved and intensive studies are to be carried on a few selected glaciers with greater water resources potential.