Ever since the inception of the State Centre on Climate Change under the aegis of the HP Council for Science Technology & Environment (HIMCOSTE) by the Government of Himachal Pradesh, the Centre has been involved in undertaking various studies to understand the impact of climate change on its various facets.
The State of Himachal Pradesh receives winter precipitation in the form of snow at the higher altitudes. About 1/3rd 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 (Env.S&T)-cum-Member Secretary (HIMCOSTE) D.C. Rana informed that although we have the information about the total snow fall that takes place during winter season from the various observatories operating throughout the State as a point information but its spatial extent reflecting about the how much area is under snow 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 winter season.
He further said that the 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 April 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 spatial resolution of 56 mts w.e.f October 2023 to April 2024. During this period , the snowfall was estimated and analyzed with reference to the average value of the total area under snow in each month from October to April.
Based on the study carried out, the following inferences were drawn:
• During early winter months of 2023-24 (October to November), all three basins viz. Chenab, Beas, and Satluj shows negative trends in the area under snow cover w.r.t 2022-23, whereas Ravi shows a marginal increase in the area under snow during 2023-24 reflecting a positive trend.
• During peak winter months (December to February), all basins show a declining trend in the area under snow except Satluj that shows a positive trend (2% in December) in 2023-24 w.r.t 2022-23 peak winter months. The results obtained for the peak winter months reveals that the decline was maximum in the month of January in all the basins with Chenab (42%), Beas (43%), Ravi (64%) and Satluj (67%) during 2023-24 winter in comparison to 2022-23 respectively. The snow cover in February in all the basins shows a positive trend and the area under snow is increased during this period.
• During the month of March 2024, same positive trend was observed in each basin in March reflecting increase in the area under snow during this period in 2023-24 in comparison to 2022-23. Likewise, at the beginning of the ablation period i.e. April, the winter precipitation extended to April as a result of which an enhancement of area is seen in each basin.
Thus, based on the overall analysis, it is observed that in Chenab basin 15.39% decline has been observed in 2023-24 in comparison to 2022-23, whereas in Beas the decline was of the order of 7.65%, in Ravi the decline was 9.89% and in Satluj, the decline was of the order of12.45% in 2023-24 in comparison to 2022-23 in terms of the total spatial distribution of the snow cover area with an overall decline of about 12.72% in the entire H.P. Himalaya covering all the four basins i. e Chenab, Beas, Ravi and Satluj based on the monthly average of the area under snow cover in each basin in 2023-24 in comparison to 2022-23, which was about 14.05% in 2022-23 winter time.
The higher rate of decrease in the Chenab basin reflects that winter precipitation during 2023-24 was comparatively weak in nature as the topographic location of the Chenab basin is such that it is presumed to receive more snow because of the WDs, that originates from the Mediterranean region enters through Afghanistan, Pakistan, Jammu Kashmir and then Himachal giving more precipitation in the Lahaul Spiti area before crossing the Pir Panjal Range that controls the western disturbance in other basins in the State.
Prabodh Saxena, IAS, Chief Secretary, Govt. of Himachal Pradesh on this study apprised that HIMCOSTE has been carrying the studies on the Himalayan snow and glaciers for the last more than three decades and had generated the database on this part of the Western Himalayan Region. As reported based on the various studies, the temperature on the Higher Himalayan region is comparatively higher than the low-lying areas which is affecting our Himalayan reserves, and is evidenced by the fact that most of the glaciers are losing mass.
Besides this, a large shift has also been observed in the snow fall patterns during winters affecting the river discharge during the peak summer season. He further said that we have also seen the rising temperature effects during winters in Shimla experiencing almost negligible snow spells during the last two winters, which seems to be major change in the weather patterns and if this continues, we have to think upon as we may have shortage of water in the coming years.
There is need to take serious note on this and hopeful that the concrete steps taken by the Government like introduction of e-vehicles, shifting to renewable energy etc. would definitely help in reducing the GHGs emissions, so that the rise in temperatures could be checked even at micro scale as well.
