Shimla, July 12 : The snow cover mapping in Himachal Pradesh from October last year to May this year showed a marginal fall of about 0.72 per cent in the total area as compared to the previous year, a government study said on Sunday.
The total area under snow cover in 2018-19 was 20,210 sq km which was reduced to 20,064 sq km in 2019-20, the Centre on Climate Change of the Himachal Pradesh Council for Science Technology and Environment (HIMCOSTE) said in a statement here.
During the peak winter months, the snow cover area 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 river 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 cover during this period, it said.
Based on summer month analysis, 65 per cent in the Chenab basin and 50 per cent in Satluj will contribute as snow melt in the river system after May onwards in comparison to Beas (45 per cent) and Ravi (26 per cent) of the total basin area this year.
The Centre has been undertaking cryosphere studies in the Himalayan range in the state by using space technology to understand the impacts of climate change.
About one-third of the total geographical area of the state remains under thick snow cover during the winter.
Most of the major rivers -- Chenab, Beas, Parvati, Baspa, Spiti, Ravi and Satluj, and their tributaries originating from the Himalayas -- depend upon the seasonal snow cover for their discharge.
Also, the snow cover helps in controlling the accumulation and ablation patterns of the glaciated regions.
"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," HIMCOSTE Member Secretary, D.C. Rana, said.
He said the studies for mapping of seasonal snow cover in river basins helped understand the contribution of snow in different catchments to sustain the hydrology of the river basins.
In 2019-20 winter in the south eastern part, there was more snow covering mainly the Satluj basin compared to Beas and Ravi basins, whereas Chenab had not shown much change in the snow cover when compared to 2018-19.
In October, February and March, all basins showed less snow cover area in 2019-20 as compared to 2018-19, indicating the winter precipitation after January had declined during the remaining winter months.
The analysis of summer months revealed that in the Chenab basin, about 87 per cent of the total basin area in April and about 65 per cent in May was still under the impact of snow, reflecting tat snow in about 22 per cent of the total basin area melted during this period.
"In other words, we can say that about 65 per cent of the total Chenab basin area would melt during the next ablation month (June to August), contributing to the runoff," Rana explained.
Likewise, the Beas basin had about 49 per cent snow cover in April and 45 per cent in May, which reflects that 4 per cent snow cover had melted.
In the Ravi basin, about 44 per cent of the total basin area in April and about 26 per cent in May was under snow cover. About 18 per cent of the total basin area melted between April and May.
Likewise, the Satluj basin comprising Baspa, Pin and Spiti rivers indicates that 72 per cent in April and about 50 per cent in May was under snow and about 22 per cent snow cover melted between the two months, said the study.