Glacial Outburst in Sikkim

On 4 October, heavy rains caused the glacial South Lhonak lake to breach its banks. This resulted in the glacial lake outburst flooding in Teesta River. The flood reached the Teesta III Dam at Chungthang at midnight, before the gates could be opened, destroying the whole dam in minutes.

The huge water over Lhonak Lake in North Sikkim resulted in a flood like situation in the Teesta River in Lachen Valley and affected nearly a lakh people. According to latest reports, 74 deaths have been con- firmed which includes nine army personnel whose bodies have been recovered from the slush and debris of the flash flood in the Teesta River. 

Many people were missing. According to officials, the search is ongoing for over 105 individuals. are still missing. neighbouring West Bengal, the Jalpaiguri district authorities recovered 40 bodies downstream of the Teesta River which flows down to Bangladesh. Rescue efforts are in progress, with hundreds of people having been evacuated from various areas of the state, the Sikkim State Disaster Management Authority (SSDMA) reported.

The water-monitoring apparatus maintained by the Central Water Commission (CWC) reported that water levels surged nearly 60 feet above the maximum levels at Sangkalang and gushed at nearly 55 kmph. This is, at the very least, thousands of cubic metres of water in a short time and the timing of water reaching dangerous heights were at
midnight, there was “very little lead time” for people downstream to react. Importantly, the National Disaster Management Agency (NDMA) reported: “... the primary reason for the sudden surge appears to be a likely combination of excess rainfall. The lake is at a height of 5,200 metres with a towering ice-capped feature at about 6,800 metres to the north of and in close proximity to the lake.” 

Heavy rainfall of course might have tipped the moraine to collapse, but India Meteorological Department (IMD) officials also admitted that at “such a height there is/was no monitoring of rainfall”. Obviously, questions could be raised as to why there was ‘no functioning early warning system’ in place already, especially since the lake has long been known to be dangerous. The lake’s area had expanded more than 2.5 times in the past three decades because of a rapidly melting glacier that feeds it. In 2016, authorities drew out some of the lake’s water to prevent it from over-flowing.

Reports claimed people working at the Chungthang dam, which is downstream of the Teesta River and collapsed because of the flood, told local media that when they received orders to open the dam’s floodgates it was already too late. Sikkim alone has more than 700 small and large glacial lakes of these around 20 are at “risk” of bursting! Whole of Himalayas are full of many such glacial lakes. 

Source: Himalayan News Chronicle