New lakes emerge in river basins due to rapidly melting glaciersUpdated: Jan 02, 2020 22:15 IST
The fragile topography of Himachal is gradually changing due to climate change brought on by global warming. Studies have revealed that rapidly melting glaciers have led to the formation of numerous lakes in the basins of perennial Himalayan rivers, including Sutlej, Chenab , Beas and Ravi and their tributaries over the last five years .
Studies conducted by the State Council For Science Technology And Environment’s state centre on climate change that were compiled last week reveal that the number of lakes in river basins in Himachal has been growing at an alarming rate.
The centre has been conducting different studies in the Himalayan ranges of the state since 1993. The centre for climate change used satellite data in 2018 to analyse the distribution of lakes in different river basins across the state.
An analysis of images captured between 2015 to 2018, revealed that the Sutlej basin has a total of 769 lakes, of which 663 are of smaller dimensions (below five hectare), 57 lakes have an aerial range between five to 10 hectare and 49 lakes extend over 10 hectare. Studies reveal that an additional 127 lakes have sprung up in the basin since 2017. Indicating, an overall increase of around 16% in the Sutlej basin.
In the Chenab basin (Chandra, Bhaga, Miyar), a total of 254 lakes could be delineated. There are 64 lakes in the Chandra sub-basin, 84 lakes in the Bhaga sub-basin and 106 in the Miyar sub-basin, respectively.
The Chenab basin had 192 lakes in 2015, however the number had increased to 254 in 2018. Startlingly, the science technology department had only recorded 55 lakes in the Chenab basin in 2001.
“Aerial measurements of the lakes indicate that 240 lakes have an area less than five hectare, 10 lakes cover five to 10 hectare and four extend over an area of 10 hectares. This reveals a reduction of around 20% in bigger lakes,” says science and technology principal scientific officer SS Randhawa.
Bucking the trend, less lakes were found in the Parvati sub-basin in 2018, indicating a 35% decrease in lakes in comparison to 2017. Scientists believe that the reason for this anomaly is the high cloud cover in the Jiwa basin.
Of the 65 lakes in the sub-basin, 58 lakes were small, with an area below five hectare, four lakes had an aerial range between five and 10 hectare and three lakes had an area more than 10 hectare in 2018, indicating an overall reduction of about 36% for small lakes and a drop of 25% in case of bigger lakes with an area above 10 hectare since 2017. No change was apparent in lakes with an area between five to 10 hectares.
In the Ravi basin, 66 lakes were documented in 2018, while only 54 had been mapped in 2017. Studies
indicate that three lakes had an area above 10 hectares,
two lakes had an area between five to 10 hectare and 61 lakes were spread over less than five hectares.
Data collected between 2015 and 2018 reveal that the lakes in the Beas basin recorded a drop of 36% , there has been a 32% increase in the Chenab basin, 94% increase in the Ravi basin and 97% increase in the Sutlej basin.
“The larger lakes have potential to cause immense damage should they burst. They need regular monitoring between July to September to assess change in their spatial extent. Thus, a proper monitoring and chain analysis of such lakes in Himalayan region of the state is critical for averting future eventualities in state,” said HIMCOSTE director-cum-member
secretary DC Rana.