Why glacial lakes above Tawang are watched, as Arunachal Pradesh argues over dams on its rivers

Background

This standing fact sits behind the dispute over big hydropower projects on Arunachal Pradesh's rivers. A glacial lake outburst flood happens when the loose wall of rock debris or ice holding back a glacier-fed lake gives way and the water runs down the valley in a surge. Such a surge can reach a dam or a settlement far downstream within hours, which is why these lakes are mapped and ranked by risk. The National Disaster Management Authority has sent expert teams to six high-risk glacial lakes in Arunachal Pradesh to assess the danger they pose. Tawang district, in the north-west of the State, holds several of the lakes placed in the highest risk class. Risk work on such lakes runs through the National Disaster Management Authority at the centre and the State Disaster Management Authority in the State, both created by the Disaster Management Act, 2005. Measures used elsewhere in the Himalaya include lowering a lake's water level and building early warning systems downstream.