Rapid glacial melt puts India, Pakistan at high flash flood risk

7,253. The number has become well-known over the past few days; it’s the number of glaciers in Pakistan, widely considered to be the highest concentration of glaciers outside the poles (it is).

7,253. The number has become well-known over the past few days; it’s the number of glaciers in Pakistan, widely considered to be the highest concentration of glaciers outside the poles (it is).

People watch as a section of a road sinks in Pakistan’s northern Swat Valley. (AFP)

A comparable number for India isn’t available. There’s a widely cited Isro report, which puts the number at 9,575, which would mean the country has more glaciers than Pakistan. Experts say the confusion arises because some of these lie across the line of control, which isn’t a recognized international border.

Still, this isn’t a cricket match to keep score. It is something far more serious.

Catastrophic floods in Pakistan over the past two days have revealed the vulnerability of that country to a warm summer — this year saw a heatwave across Pakistan and India in May — that results in a higher volume of glacier run-off on account of melting ice, followed by extreme monsoon rain.

At least 1,000 people have died already in Pakistan, on account of floods that are already being described as once-in-a-lifetime; millions have been displaced.The flash floods in vast swathes of the country, from north to south, with most rivers, including the Indus, Kabul, and Swat in spate.

The trigger for the flooding was extreme rain over the past few days, arising from a well-marked low pressure area which formed over Bay of Bengal on August 19 and travelled across central India to Pakistan. But as Sherry Rehman, Pakistan’s climate change minister told The Guardian, higher temperatures caused glaciers in the country’s north to melt faster, amplifying the impact of the rain. She added that Pakistan was experiencing “serious climate catastrophe, one of the hardest in the decade”.

It hasn’t escaped some researchers’ attention that the Chitral Valley is among the worst affected — with 543 glaciers in the surrounding mountains, the valley has long been at risk from glacier melt.

Glaciers in the Hindu Kush Himalayas on the Indian side are also extremely vulnerable to high run-off, glacial lake outburst floods, and other related disasters due to a rapid trend of retreat associated with the climate crisis.

“Glacial melt water is increasing. When there is heavy precipitation along with warming, glacial meltwater adds to the run off. This problem will be felt in India also when glacial melt adds to increased run off and floods,” explained R Krishnan, director of Indian Institute of Tropical Meteorology in Pune who specialises in climate modelling, global and monsoon hydrological cycle changes. The Hindu Kush Himalayan (HKH) region covers around 3,500km across Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal, and Pakistan.

But India’s vulnerability to glacial melt floods is not as high as Pakistan, added Anil Kulkarni, a glaciologist and distinguished scientist at the Divecha Center for Climate Change. “I would say India is not as vulnerable as Pakistan to glacier melt floods. Glacier-stored water in Indus Basin is around 2103 cubic km. Out of this around 95% is stored in the western river basin which is allotted to Pakistan. Glacier mass loss is high in Satlej and Beas basins. In Ganga and Brahmaputra basins in India, the contribution of glaciers in stream run-off is comparatively smaller. It is around 20-25% as compared to 60% in the Indus basin. Therefore, Pakistan may be more vulnerable.”

But he admitted that “glaciers on both sides are seeing rapid mass loss”.

Kulkarni believes India should prepare for challenges arising from rapid glacier melt: “Reduction (in the long-run) of stream run-off in the rivers; changes in seasonality of water availability in glacier fed rivers; drying of Himalayan springs; flash floods due to Glacial Lake Outburst Floods (GLOFs); and new geopolitical challenges among several other concerns.”

India is no stranger to all of these. A flash flood believed to have been caused by a glacier lake outburst in 2021 in Chamoli, Uttarakhand, killed over 200 people. Failure of ice or moraine dams leading to disastrous flood events are called as Glacial Lake Outburst Flood (GLOF), which have immense potential of flooding in downstream area.

The glaciated area of the Hindu Kush Himalayas is around 42,000 sq km of which around 25,000 sq km is in India according to Kulkarni but it is difficult to state how many glaciers are in India mainly because of border related debates, he added. “If you go by the conventional map of India, for instance, most glaciers are in India.” The HKH has the largest extent of cryosphere (glaciers and ice caps, snow, river and lake ice, and frozen ground) outside the polar regions according to International Centre for Integrated Mountain Development.

It’s also important to understand the combined effect of glaciers melting, with extreme rain events.

“Interestingly what brought extreme floods to Pakistan was actually a monsoon depression that travelled from central India. Normally, these monsoonal systems weaken over central India or Rajasthan. It’s very unusual that the depression travelled up to Pakistan. There is a lot of soil moisture over central India, just like a tropical cyclone moves over the ocean and gains intensity, this system travelled over land and the extreme wet conditions of the soil provided feedback because of which it did not weaken. So glacial melt may not be the primary reason for flooding in Pakistan,” said M Rajeevan, former secretary, ministry of earth sciences.

But it is known that “ glacial melt run-off will lead to floods”, he added. “Entire northwest India particularly Punjab, Uttarakhand, Himachal Pradesh etc are vulnerable because the glacial melt is more severe in the western Himalayas. But we do not have good qualitative data to study these impacts and that is a huge challenge.”

The reason for the extreme rain is an obvious one: the climate crisis, said Ananda Das, cyclones in-charge at IMD. Extreme rain events are increasing in frequency, even in India, he explained. “Such extreme rain events are now being recorded in places which are not prone to heavy rain.”

Flooding from the Swat River overnight affected northwestern Khyber Pakhtunkhwa province, where tens of thousands of people — especially in the Charsadda and Nowshehra districts — have been evacuated from their homes to relief camps set up in government buildings according a report by Associated Press on Sunday.

“Assessment of Climate Change over the Indian Region,” a report by ministry of earth sciences (MoES) released in 2020 highlighted that a there has been a significant rise in surface temperatures throughout the Hindu Kush Himalayan region over the past six decades. The warming was reported progressively over the western and eastern Himalayan River basins, and there is a long-term trend of increasing minimum temperatures, the report said. The Hindu Kush Himalayas experienced a temperature rise of about 1.3 degrees Celsius during 1951-2014 compared to average temperature rise by around 0.7 degrees Celsius during 1901-2018 across the country.

The results have been evident for some time. Several areas of HKH have experienced a declining trend in snowfall and also retreat of glaciers in recent decades. In contrast, the high-elevation Karakoram Himalayas have experienced higher winter snowfall that has protected the region from glacier shrinkage. By the end of the 21st century, the annual mean surface temperature over HKH is projected to increase by about 5.2 degrees Celsius under a high emission scenario.

At least 30,000 sq km of the Himalayan region is covered by glaciers which provide about 8.6 million cubic metres of water every year according to Nasa data referred by the MoES report. Almost all glaciers in the vicinity of Mount Everest have experienced a retreat from the late 1990s, the report said. The Gangotri glacier in India, which provides a significant source of meltwater for the Ganges, has lost approximately 0.23 sq km area due to the retreat of the glacier between 2001 and 2016, according to Centre’s reply in Rajya Sabha based on data from Indian Space Research Organisation.

An analysis estimates a loss in glacier area by about 13% during the last four decades. “Future warming in the HKH region, which is projected to be in the range of 2.6-4.6 degree C by the end of the twenty-first century, will further exacerbate the snowfall and glacier decline leading to profound hydrological and agricultural impacts in the region,” the report added.

In all emissions scenarios, average annual and summer run-off from glaciers are projected to peak before the end of the 21st century. For example in High Mountain Asia, which includes the Hindu Kush Himalayas, glacier run-off will peak around mid-century followed by a decline according to Intergovernmental Panel on Climate Change’s “Special Report on the Ocean and Cryosphere in a Changing Climate” released in 2019.

What’s happening in Pakistan is a demonstration of a worst-case scenario foretold in that report.