Bhotekoshi flood: Study finds 23 Uttarakhand glaciers retreating rapidly

KATHMANDU, Sept 20: The Bhotekoshi flood that struck the Nepal–China border region on August 26 has renewed concern about climate change and melting glaciers across the Himalayas.

A massive avalanche near Langtang Lirung generated seismic tremors measuring 5.2 on the Richter scale. An estimated 74 million cubic metres of ice, rock and debris fell into the Lhende River.

The resulting flood and debris flow began in Tibet and crossed into Nepal, causing extensive damage in Rasuwa, Nuwakot and Dhading, among other districts. Search and rescue operations were still under way 25 days after the disaster. The flood caused heavy loss of life and property in Nepal and China.

As questions grow about the causes of such disasters and the effects of climate change, a study has found that 23 major glaciers in India’s Uttarakhand state are retreating rapidly. Rising global temperatures are affecting the Himalayan region, the researchers said. A glacier’s shape, slope and covering of debris also influence how quickly it loses ice.

Scientists Jyoti Kumari, Girish Chandra Kothiyari, Atul Kumar Patidar and Manish Mehta of the Wadia Institute of Himalayan Geology published their research in Discover Geoscience. They examined historical records for 23 glaciers to assess the causes and rates of retreat.

The study was reported days after the Bhotekoshi flood. According to NDTV, large pieces of ice have broken away from glaciers and moved down valleys more often in recent years, drawing attention to risks in the Himalayas.

Himalayan glaciers supply water for drinking, irrigation and hydropower in India and neighbouring countries. Major rivers originating in the region include the Ganga, Bhagirathi, Sutlej, Ravi, Indus, Brahmaputra, Yamuna, Alaknanda and Mahakali.

Uttarakhand has hundreds of glaciers, including Gangotri, Alkapuri, Milam, Pindari, Khatling, Satopanth and Bhagirathi. The study found that many have retreated substantially.

In Pithoragarh district, the Shankulpa glacier retreated 518 metres over seven decades, an average of 6.8 metres a year. The Bandarpunch glacier in Uttarkashi retreated at an average of 25.51 metres a year between 1960 and 1999. In Rudraprayag, the Chorabari glacier retreated 327 metres between 1962 and 2010, averaging 6.8 metres a year. Khatling in Tehri retreated at a reported rate of 88 metres a year.

Researchers examined Gangotri over two periods. It retreated at an average of 22.02 metres a year between 1935 and 2004, and 21.3 metres a year over a later six-year period.

The study recorded annual retreat rates of 21 metres for Dokriani, 3.7 metres for Bhagirathi, 26.45 metres for Satopanth, 14.41 metres for Tipra and nine metres for Dunagiri. Milam retreated by 32 to 37.8 metres a year, North Nanda Devi by 22 metres and Ramani by 32 metres.

Pindari’s retreat also accelerated across the periods studied. It moved back 2,840 metres between 1845 and 1966, an average of 23.4 metres a year. Between 2000 and 2018, it retreated 825.23 metres, averaging 45.85 metres a year.

The researchers identified Khatling, Milam, Gangotri, Satopanth, Ramani and Jaundhar among the glaciers retreating rapidly. Milam and Khatling have shown particularly fast retreat in recent years. Their review found that glaciers covered in debris generally retreated by a few metres a year, while those with exposed ice retreated faster.

Continued glacier loss could contribute to rising sea levels and increase the risk of glacial lake outburst floods, avalanches and debris flows, the report said. It also noted faster melting since 2000. Rain now falls at elevations of up to 4,000 metres where snow was once more common, while summers have lengthened and winter snowfall has declined.