Climate change: Snow cover declines in major river basins of Himachal Pradesh

The state witnessed a marginal decrease of about 0.72% in its snow cover from October 2019 to May this year in comparison to 2018-19 i.e total average area under snow has reduced from 20210.23Km2 to 20064.00Km2

Rapidly changing climate is degrading the snow cover of Himalayan rivers originating in Himachal Pradesh, according to a recent study by the State Centre on Climate Change under the aegis of the Himachal Council for Science Technology and Environment (HIMCOSTE).

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The state witnessed a marginal decrease of about 0.72% in its snow cover from October 2019 to May this year in comparison to 2018-19 i.e total average area under snow has reduced from 20210.23Km2 to 20064.00Km2. Further, during peak winter months, the snow cover area has reduced gradually from February onwards which may affect the runoff patterns during the summer months. Based on the data analysed, more snow cover has been observed in the Satluj basin during winter months (November to January) than the Beas and Ravi basins, whereas the Chenab basin has not shown much change in the area under snow during this period. Based on summer month analysis, in Chenab basin (65% of the total basin area) and Satluj basin (50% of the total basin area) will contribute as snowmelt in the river system after May onwards in comparison to Beas basin (45%) and the Ravi basin (26%) of the total basin area this year.

State Centre on Climate Change has successfully utilised the applications of space technology in carrying out studies related to Cyrosphere comprising the snow and glaciers in Himachal in collaboration with Space Applications Centre (ISRO), Ahmedabad. The Cryospheric studies are important as the one-third part of the state is characterised by this great Himlayan reserve and the studies of which using any other conventional method is not possible due to the inaccessibility of this area.

Himachal Pradesh receives winter precipitation in the form of snow at the higher altitudes. About one-third of the total geographical area of the state remains under thick snow cover during the winter season. Most of the major rivers like Chenab, Beas, Parvati, Baspa, Spiti, Ravi, Satluj, and its perennial tributaries originating from the Himalayas depend upon the seasonal snow cover for their discharge dependability. Besides this, the snow cover also helps in controlling the accumulation and ablation patterns of the glaciated regions in the state.

Considering the importance of seasonal snow cover as a major input in controlling the hydrology of the river basins, director (environment science and technology)-cum-member secretary (HIMCOSTE) DC Rana said that although we have the information about the total snowfall that takes place during the winter season from the various observatories operating throughout the state as point information and therefore its spatial extent cannot be ascertained. Thus by using satellite data of different resolutions, it has now become possible to map the geographical extent of the area covered under snow during the winter season.

He added that studies which are being carried out by the Centre for mapping of seasonal snow cover in terms of its spatial distribution covers the different river basins in Himachal Pradesh during the winter season from October to May and is an important input in order to understand the contribution of snow in different catchments to sustain the hydrology of the river basins.

Considering the present trend of winter snowfall in Himachal Pradesh, the winter precipitation was mapped in all the basins viz Chandra, Bhaga, Miyar, Beas, Parvati, Jiwa, Pin, Spiti and Baspa using AWIFS satellite data having a spatial resolution of 56 mts from October to May. During 2019-20 snowfall was estimated and analysed with reference to the average value of the total area under snow in each month from October to May in 2018-19, he added.