RN-38 : Measurement of snow and estimation of snow cover

Abstract

The rivers draining out of the Himalayan region derive a major portion runoff from snow and ice melt. For runoff forecasting, irrigation planning, supply of drinking water and industrial use etc. reliable and adequate information on snowfall and snow cover as well as their water equivalent is required. Know-ledge of the physical characteristics of the snow cover such as its density, depth and temperature, and their variability in time and space is necessary for hydrologists. A careful survey of snow covered area with its water equivalent in conjunction with observations of atmospheric factors can also lead to flood forecasts and general hazard warning.

Snow cover is a residual project of snowfall and has characteristics different from those of freshly fallen snow. The snow surveys made by traditional methods involve much time and labour. The advent of remote sensing has opened up new avenue for snow cover monitoring and assessment. Once a correlation between areal extent and ground truth has been established. the prediction models can be extended with suitable modifications to other areas where ground truth is not available. With adequate knowledge of gauge characteristics and limitations. gauge catch deficiencies may be minimized and reasonable data adjustments could be made. Further studies to find out the effect of weather and exposure on snowfall measurements are required achieve improvement in catch efficiency of the snow gauges.

There is need for basic research on snow cover accretion and depletion, their relation to meteorological and terrain factors. The development of appropriate techniques would require investigations through entirely new approaches free from the deficiency caused by poor exposure and redistribution problem. The point measurements made in representative locoation is critical interpretation and applying point measurements as areal indices. Moreover, studies correlating snow covered area and subsequent melt water runoff would set the pace for further application of satellite data in this important area of hydrology.