Expeditions to study high-risk glacial lakes in Himalayas begin

The NDMA has identified 189 high-risk glacial lakes in the Indian Himalayas and launched a ₹150-crore program for risk mitigation, including monitoring and early warning systems.

Over the last few months, around 16 teams of officials from the National Disaster Management Authority, scientists and security officials have taken up expeditions to glaciers at an altitude of 4500m and above to map the threat they could pose to populations downstream in the event of a glacial lake outburst.

Of the nearly 7,500 glacial lakes in the Indian Himalayas, NDMA has found 189 high-risk lakes that require mitigation measures.

Of the nearly 7,500 glacial lakes in the Indian Himalayas, NDMA has finalized 189 high-risk lakes that require mitigation measures, NDMA officials said.

The Centre has now approved the ₹150-crore National Glacial Lake Outburst Floods Risk Mitigation Programme (NGRMP) on July 25, the officials said.

The programme aims at detailed technical hazard assessments, and installing automated weather and water level monitoring stations (AWWS) and early warning systems (EWS) at the lakes and in downstream areas.

The primary objective of this programme is to attempt lake-lowering measures to reduce the risk of GLOF from such lakes.

Depending on the state of a glacial lake is found to be in, a range of mitigation measures can be taken, said Safi Ahsan Rizvi, advisor (mitigation), NDMA.

“Satellite imagery and historical research has led us to categorise 189 lakes as high risk. These are now undergoing ground-truthing. Then three simultaneous activities will be done a) Placement of automated weather and water level monitoring stations and early warning systems b) digital elevation modelling and bathymetry and c) assessing best means to reduce the risk of that lake including by lake-lowering,” Rizvi said.

But monitoring the state of these high-risk glaciers involves surveying them manually. Of the 16 teams that set out for their expeditions, one could not reach the spot due to inclement weather.

“Others have returned with relevant data, which the states will now use to finalise their mitigation strategies,” said Safi Ahsan Rizvi, advisor (mitigation), NDMA.

Each team consisted officials and assistants ranging from five to 20, and included scientists, officials and security forces and their expeditions, on foot, took three to seven days.

Of the 15 expeditions completed, six were in Sikkim, six in Ladakh, one in Himachal Pradesh, and two in Jammu and Kashmir. “Another seven expeditions are underway. Given the inhospitable terrain and weather conditions at heights of 4,500 m and above, there is only a June to September window to approach these formidable lakes. Several visits will be needed to implement lake-lowering measures, some of which could require civil engineering,” a note by NDMA on the project said.

These composite expeditions are assessing structural stability and potential breach points of glacial lakes, gathering relevant hydrological and geological samples and data, measuring water quality and flow rates, identifying risk zones and making downstream communities aware.

The study of glacial lakes was necessitated after recent incidents involving outbursts.

On August 16, flashfloods struck Thame, a village in the Khumbu region of Nepal which was due to an outburst flood from Thyanbo glacial lake.

An initial assessment of damage by the local authorities shows 14 properties have been destroyed, including one school, one health post, five hotels and seven homes. Several glacial lakes lie upstream of Thame. Satellite images of the area dating back to 2017 obtained by International Centre for Integrated Mountain Development (ICIMOD) from the European Space Agency’s Copernicus earth observation programme show these lakes constantly changing in size. Researchers at ICIMOD confirm that some of them frequently expand and contract, making them susceptible to breaches.

ICIMOD’s 2023 assessment, Water, Ice, Society, and Ecosystems in the Hindu Kush Himalaya, stated that the glaciers, snow, and permafrost of the Hindu Kush Himalaya are “undergoing unprecedented and largely irreversible changes over human timescales, primarily driven by climate change” and “are some of the most vulnerable to these changes in the world”.

ICIMOD warned that floods and landslides are projected to increase, with climate the key driver in many of the water- and cryosphere-related disasters already recorded in recent years, through meltwater, larger and more potentially dangerous lakes, unstable slopes from thawing permafrost, and increasing sediment loads in rivers.

In India too, Uttarakhand saw glacier breach induced flash floods in February 2021 Rishi Ganga valley killing over 200 people, nearly washing away two hydropower plants, while also damaging Raini village, a historical border village where the Chipko movement was active.

Last year, there was a Glacial Lake Outburst Flood (GLOF) in portions of Lhonak Lake in Sikkim which caused water levels to rise with very high velocities downstream along the Teesta River Basin in the early hours of October 4. The GLOF caused extensive damage including to the Teesta III dam.

NDMA expects risk from glacier disasters to escalate in the coming years. “There are several studies and assessments on the impact of climate change. While attribution science on which weather anomaly is caused by which element of climate change is still in flux, India has to deal with two daunting hazards. One, extreme altered FDI (frequency, duration and intensity) of precipitation and two, extreme heat,” Rizvi explained.

“Both these factors impact glacial melt, which increase the volume of water in glacial lakes, thereby threatening the inherent stability of weak moraine dams,” he said.

All technical agencies, including National Remote Sensing Centre (NRSC), Central Water Commission (CWC), Geological Survey of India (GSI), Defence Geoinformatics Research Establishment (DGRE), National Geophysical Research Institute (NGRI), National Institute of Hydrology (NIH), Wadia Institute of Himalayan Geology (WIHG), Indian Army, Indo-Tibetan Border Police (ITBP) among others and an international agency the Swiss Agency for Development and Cooperation (SDC) are involved with the States in planning and implementing this programme. There is a separate programme envisaged on the same lines for J&K and Ladakh, Rizvi said.