A satellite image of Lhonak Lake in North Sikkim.
Nearly 65 per cent of Sikkim's Lhonak Lake - around 105 hectares - has been drained after a cloudburst forced the water body to overflow and trigger flash floods in the Teesta River.
Temporal satellite images (referring to before-and-after) released Wednesday evening by space agency ISRO show dramatic changes in the volume of water in the lake; photos taken on September 17 and September 28 show the bullet-shaped lake holding 162.7 and 167.4 hectares, respectively.
An image taken at 6 AM Wednesday morning - after the cloudburst and flash flood wreaked havoc in the state, washing away large parts of a hydroelectric project and leaving 49 people missing - shows the lake reduced by more than half and with only an estimated 60.3 hectares of water in it.
READ | Cloudburst In Sikkim Triggers Flash Floods, Soldiers Among Missing
"Temporal changes in the lake area - as on September 17, September 28, and October 4. It is observed the lake is burst and about 105 hectares has been drained out, which might have created a flash flood downstream... will continue monitoring the lake using the satellite data," ISRO said.
Temporal satellite images of Lhonak Lake in North Sikkim.
The floods have killed at least eight people, news agency PTI said citing unnamed officials who also said three bodies were found hundreds of kilometres downstream in north Bengal. The other five were found in the state's Golitar and Singtam areas, Gangtok district officer Mahendra Chettri said.
23 soldiers are among those missing. The Army and local officials have launched a joint rescue op.
45 people have been rescued, of whom 18 have suffered injuries, PTI reported.
There was heavy rainfall in Sikkim overnight; the weather department said the northern part of the state, where the lake is, received nearly 50 mm from Sunday - 48 per cent more than normal.
READ | Parts Of Teesta River Dam Washed Away After Cloudburst In Sikkim
Other parts of the state received even more rain; eastern areas saw 315 per cent unseasonal rainfall while South Sikkim got a massive 943 per cent more. West Sikkim got 50 per cent extra rain.
The cloudburst over Lhonak Lake not only caused that to overflow but also pushed up water levels in the Teesta, which flows through Sikkim and Bengal before entering Bangladesh.
The overflowing Teesta also swept away parts of a dam at Chungthang, which is the state's largest hydropower project. The Army said the level of water flowing through the dam led to a sudden increase of 15-20 feet downstream.
Visuals also showed catastrophic floods in North Sikkim's Mangan district.
A steel bridge at Singtam, which is 30 km from Gangtok, was completely destroyed.
Sections of National Highway 10 were washed away and several other roads were damaged, making access to Gangtok, Pakyong, Namchi, Gyalshing, Soreng and Mangan districts extremely difficult.
Residents in low-lying areas of Chungthang and Singtam have been evacuated.
"Nobody has been injured but there is significant damage to public property. Relief operations are on," Sikkim Chief Minister Prem Singh Tamang said during a visit to affected areas.
Prime Minister Narendra Modi said he had spoken to the Chief Minister Tamang and assured him of support.