Glacial lake that sent deadly floods through Indian towns was identified as dangerous in 2019

NEW DELHI: A glacial lake that overflowed in India's Himalayan northeast, breaking through a major dam and sending deadly, ice-cold floodwater through towns downstream, had been identified by state officials, researchers and environmental activists as dangerous years before the disaster.

The flood killed at least 31 people, officials said Friday, and forced thousands of people to flee their homes.

It began shortly after midnight Wednesday, when Lhonak Lake overflowed after a heavy rainfall. Waters from the high mountain lake crashed into the largest dam in the state of Sikkim, cracking its concrete before cascading through towns in the Lachan Valley below and sweeping away people, houses, bridges and an army camp.

The design and placement of the 6-year-old Teesta 3 dam were controversial from the time it was built, part of an Indian push to expand hydropower energy. Local activists argued that extreme weather caused by climate changes makes dam-building in the Himalayas too dangerous, and warned that the dam’s design didn’t include enough safety measures.

Floods follow unusually heavy monsoon

The deadly flood was the latest to hit northeast India in a year of unusually heavy monsoon rains.

Nearly 50 people died in flash floods and landslides in August in nearby Himachal Pradesh state, and record rains in Northern India killed more than 100 people over two weeks in July.

On Friday, hundreds of rescuers from the army and national government worked their way through slushy debris and the fast-flowing Teesta River water in still-flooded towns. They faced a challenging task, digging through cars, school buses and buildings buried in deep mud, while mobile networks and broadband connections have been disrupted in most of the district.

Officials said 100 people are missing, including 15 soldiers.

A report compiled by the Sikkim State Disaster Management Authority in 2019 had identified the lake the Teesta 3 dam was built to contain as “highly vulnerable” to flooding that could cause extensive damage to life and property in downstream areas, warning of the risk of flash floods that could break through dams.

The dam’s operator, and local agencies responsible for dam safety, did not respond to requests for comment Friday.

Dangers identified earlier

Lhonak Lake has been rising quickly over recent years, as the glaciers that feed it melt faster due to climate change. A 2021 study by researchers in India, the United States and Switzerland warned that rising waters, and the steep slopes that surround the lake, made a catastrophic flood more likely.

The Teesta 3 hydropower project, built on the Teesta River, took nine years and cost $1.5 billion to construct. The project was capable of producing 1,200 megawatts of electricity — enough to power 1.5 million Indian homes — and began operations in 2017.

“Despite being the biggest project in the state, there were no early warning systems installed even though the glacier overflowing was a known risk,” said Himanshu Thakkar of the non-governmental organization South Asian Network for Rivers, Dams and People.

According to a release from India’s National Disaster Management Agency Friday, they plan to set up early warning systems for real-time alerts at most of India's 56 known at-risk glacial lakes.

Thakkar said authorities failed to apply the lessons from a 2021 dam breach in Himalayan state of Uttarakhand that killed 81 people, allowing an “eerily similar” disaster to occur.

Despite risks to dams due to increasing frequency of extreme weather, the Indian federal government aims to increase India’s hydroelectric dam output by half, to 70,000 megawatts, by 2030.

In 2021, the Indian federal government passed a dam safety law that requires operators and local governments to plan for emergencies, but the Teesta-3 dam is not listed as being monitored for safety by India’s chief dam regulator, the Central Water Commission.

“We knew that this was coming,” said Gyatso Lepcha, general secretary of Affected Citizens of Teesta, an environmental organization based in Sikkim. “The same can happen with other dams also,” he wrote, in a statement that called for a safety review of all dams in the state.

It wasn’t clear what triggered the breach Wednesday.

Dam breaches

Experts and varying government reports have pointed to sudden, intense rains in the area, and a 6.2 magnitude earthquake that struck nearby Nepal on Tuesday afternoon.

Disasters caused by landslides and floods are common in India’s Himalayan region during the June-September monsoon season. Scientists say they are becoming more frequent as global warming contributes to the melting of glaciers there.

Last month, dam breaches caused by Storm Daniel caused devastating damage to the city of Derna in Libya.

More than 2,000 people were rescued after Wednesday’s floods, the Sikkim State Disaster Management Authority said in a statement, adding that state authorities set up 26 relief camps for more than 22,000 people impacted by the floods.

Rescue workers were still searching for nearly 100 missing people, including 15 soldiers, on Friday, according to the Sikkim state government.

One soldier was previously reported missing was rescued, and the bodies of seven have been found, state police said.

Eleven bridges in the Lachan Valley were washed away by the floodwaters, which also hit pipelines and damaged or destroyed more than 270 houses in four districts, officials said.

The army said it was providing medical aid and phone connectivity to civilians in the areas of Chungthang, Lachung and Lachen in north Sikkim, and local media reported that said the army was erecting temporary bridges to bring food to affected areas.