Glacial Lakes : National Disaster Management Authority Study
The National Disaster Management Authority (NDMA) has finalised a list of 189 “high-risk” glacial lakes for mitigation measures to reduce the risk emanating from them.
- Glacial Lakes is a body of water that originates from a glacier.
- It typically forms at the foot of a glacier, but may form on, in, or under it.
- ISRO categorised glacial lakes into four broad categories based on how they were formed — moraine-dammed, ice-dammed, erosion-based, and ‘others’.
- As glaciers move, they erode the terrain under them, leaving depressions and grooves on the land.
- When they churn up rock and soil, they etch ridges of debris known as moraines.
- Most glacial lakes form when a glacier retreats and meltwater fills the hole left behind.
- However, natural dams, formed out of ice and terminal moraines, can also form glacial lakes.
- An ice dam forms when a surging glacier, which can move up to 100 times faster than an average glacier, may dam up meltwater as it closes off a valley or fjord and prevents it from draining.
- Dams formed by moraines can be dense and stable, holding sizable lakes behind them for years.
- They can also be leaky, allowing the lake to drain slowly into nearby rivers.
- Glacial lakes are crucial sources of freshwater for rivers.
- However, they also pose significant risks, specifically of Glacial Lake Outburst Floods (GLOFs).
