RN-28 : Snowline and snow cover mapping by remote sensing techniques

Abstract

Snow and ice is a major component of Water Resources and it is hydrologically important in India because of the presence of mighty snow clad Himalayas. Major north Indian rivers originate from the Himalayas and the influence of snow in estimating runoff forecasting and reservoir operation is of great interest to hydrologists. It is more so because of the reason that snowmelt runoff is available in these rivers during March to May when there is hardly any precipitation in the catchment areas. The density and thickness of snow varies within a short distance to a great extent. So, the field measurements about snow which are point data may be misleading. Besides, the snow bound areas are remote and hazardous to access. Remote Sensing techniques, both satellite and aerial flight offer an excellent synoptic view in various spectral channels of electromagnetic spectrum which serve as a spatial data base for snow related studies. Repetitive coverage of satellite also provides scope to monitor snowline movement and other characteristics of snow. Delineation of snow in a imagery is relatively simple because of its high reflectance. Problems like location, recognition and measurement in targeting snow and ice in remote sensing are minimum and as such monitoring of snow cover areas by remote sensing could be made automatic and operational.

Amongst various sensors in different available satellites Land sat MSS band 5 (0.6 - 0.7 pm) ,NOAA visible channel data are most suitable. However, other properties of snow like density, thickness, water equivalent etc. are becoming viable to be measured by remote sensing as technology progresses and improved sensor systems are put on-board the satellites.

Gamma ray, thermal infrared and microwave portion of electromagnetic spectrum have great potential for snow studies. The data of band 5 of thematic mapper of Landsat - 4 and 5 satellites which are now available are suitable to separate snow and cloud. The use of remotely sensed data in hydrologic modelling has also been examined and the initial findings are promising.

Considering all the available means to decipher or measure snow and ice, the remote sensing methods has definite advantages and could be judiciously used to make hydrologic studies.