A couple of earthquake tremors that originated in Nepal close to Tuesday midnight might have acted as the final trigger in the bursting of South Lhonak Lake that led to flash floods in Sikkim. The lake had already become vulnerable over the last 11 days with unusual expansion, sources in the India Meteorological Department said on Thursday.
Sources in Sikkim confirmed that the gushing of water from the lake, a volume equivalent to 100 hectares downstream, according to an estimate of Disaster Management Support Group under the National Remote Sensing Centre, ISRO, joined the water already accumulated in Chungthang dam. This led to its partial collapse and magnified the impact that had triggered severe devastation in Sikkim and also significant damages in West Bengal.
Jairam Ramesh, Congress leader and former Union environment minister, flagged off the need to have credible environment impact assessments before allowing hydel dams to be set up in the wake of the latest disaster; echoing a demand the environmentalists have been making for a long time.
“As environment minister, I always insisted on cumulative, comprehensive and credible environment impact assessments before embarking on building dams but we never seem to learn,” he said, hinting towards the present mode of giving green clearances.
“It is another reminder of how we must learn to be more sensitive to local ecologies while planning for and executing hydel projects especially in fragile areas” he wrote in his X handle.
“Most of the hydel dams, the way they have been constructed and operate holding water for most of the time to maximise profit though they are officially supposed to be run of the river dams, are a recipe for disaster and Chungthang collapse has given us another reminder,” said an environmentalist in Bengal.
On Thursday, as the water has started to recede in Teesta, bodies have started to tumble out from several places of north Bengal, said sources in the local administration. Till Thursday, the death toll due to Teesta flash flood rose to 40 according to Reuters, while more than 100 persons are reported to be missing, including 22 army personnel.
Several are being treated in various hospitals, while few thousand tourists, along with local residents, have reportedly been stranded especially in between Lachen valley and Chungthang, the status of which remains still largely unknown as the disaster management team is struggling to reach as at least 19 bridges collapsed due to disaster, cutting out the region.
“Poor weather held back even the helicopter operation till morning,” said an official in the noon, accepting that the actual losses may be much higher.
Human-made, nature-triggered
Information, available with this reporter, shows that multiple factors including human failure acted in tandem to trigger the bursting of the lake around Tuesday midnight and magnifying the disaster; but the final trigger seems to be an earthquake that occurred near Chaukham in Nepal, about 765km away from South Lhonak Lake.
“A minor earthquake to the intensity of 3.1 in Richter scale happened at the stroke of midnight in Nepal, followed by another in the intensity of 3.7 at 12.35am in the same place (29.51º latitude, 80.71º longitude) seemed to have triggered the bursting of the glacial lake as it seemed to have collapsed around that time; incidentally there was another minor earthquake at 1.53am,” said an IMD expert.
According to the information received, the earthquake struck around Chaukham in Nepal, about 765km west of South Lhonak Lake.
Unusually high rainfall, a tell-tale example of heightening climate change impact, also seemed have contributed towards the lake burst, said experts.
“Intense rain has led to this catastrophic situation in Sikkim where the rain has triggered a glacial lake outburst flood. We observe that such extreme events increase in frequency as the climate continues to warm and takes us into unknown territory,” said Miriam Jackson, senior specialist of The International Centre for Integrated Mountain Development (ICIMOD).
ISRO data indicates that the lake had been rapidly turning vulnerable in the last few days. “If you look at the ISRO data you will find that on September 17 its area was 162.7 Ha approximately, which expanded to 167.4 Ha approximately on Sept 28; almost 3 per cent rise within 11 days … clearly signal was there and an early warning could have saved many lives,” said environmentalist Animesh Bose of nonprofit HNAF on Thursday.
“South Lhonak Lake was a ticking bomb for a long time. The In second week of September, a joint team of the National Disaster Management Authority, Sikkim disaster management authority and some consultants made a joint visit to assess the vulnerability of the lake,” said an official.
According to data available, the lake got expanded nearly five times in less than six decades.
Bodies tumble as Teesta water level goes down
Eight bodies have been found from Mainaguri in Jalpaiguri; while a body was found floating in Fulbari canal, according to the local administration. Two labourers have been reported missing in a tea garden in Jalpaiguri while two bodies were found floating in Gajoldoba Teesta barrage. The sources point out that the possibility of finding the missing persons has been steadily decreasing with time.
At least five tourists have been reported to be missing so far, two from New Delhi and three from West Bengal district of Uttar Dinajpur, while around 3000 tourists have been reportedly stranded in the area. Bengal chief minister Mamata Banerjee has already asked the chief secretary to make arrangements to rescue local residents and tourists and a team of ministers and senior officers has been rushed to north Bengal.
“We were extremely concerned about the flood risk faced by thousands living in Padamati village area within Nandapur GP, a char area downstream to Gajaldoba barrage, but fortunately the water level started to recede from the afternoon of Wednesday and there has been no fresh cause of concern today , as the rain also relented to an extent,” said Arnab Bhatacharya from nonprofit NESPON working in the area.
“We expect the rain to subside from tomorrow,” said G.K. Das, head of IMD Alipore weather section on Saturday.