NEW DELHI: Retreat of Gangotri glacier will not have drastic influence on the flow of Ganga as the river is not totally dependent on glaciers for its water even in the head-water region, said the government on Tuesday.”The percentage of snow and glacier-fed contribution progressively reduces as one moves downstream. Rainwater and sub-surface flows contribute more than 70% of the flow of river Ganga at Haridwar”, said the environment minister Anil Madhav Dave in Lok Sabha.
The minister, while responding to a Parliament Question, quoted the National Institute of Hydrology and referred to the mapping done by the country’s space agency – Indian Space Research Organisation (ISRO).
The ISRO had carried out mapping of Himalayan glaciers using lndian satellite data during 2004 to 2007. The study shows that there are 34,919 glaciers spread over 75,779 sq. km. in Indus, Ganga and Brahmaputra basins covering Himalaya and Trans-Himalaya including Karakoram region.
The ISRO had also monitored the ‘advance’ and ‘retreat’ of 2018 glaciers, across the Himalayan region using satellite data of 2000-01 to 2010-11.
Dave, in his written response, said, “The study shows that 87% of glaciers showed no change, 12% glaciers retreated and 1% glaciers have advanced”.
The minister had last week informed the Lok Sabha that majority of the glaciers in the country, including the largest one Gangotri, are melting at varying rates ranging from five to 20 metre per year.
Sharing information on Gangotri and the second largest glacier Satopanth, Dave had, however, said, “Both the glaciers are retreating (melting) but not at an alarming rate”.
He had referred to the studies carried out by ISRO, Wadia Institute of Himalayan Geology (WIGH), Dehradun and other institutions and said the studies carried out on melting of glaciers by the in-situ measurements as well as remote sensing data indicate that the rate of retreat was “not uniform” for all glaciers.
Giving an example, Dave had said Dokriani glacier in Bhagirathi basin was retreating between 15 and 20 metre per year since 1995 whereas Chorabari glacier in the Alaknanda basin was retreating 9-11 metre per year during 2003-2014.
The minister had a study on length and area changes of 82 glaciers located in the Bhagirathi and Alaknanda river basins has been carried out for a period of 1968-2006 using remote sensing data and the study suggests that glacier area decreased from 599.9 sq km (1968) to 572.5 sq km (2006), implying a net loss of 4.6% of the total area.
However, glaciers in the Alaknanda basin and upper Bhagirathi basin lost 18.4 sq km (5.7%) and 9.0 sq km (3.3%) respectively during the same period.