Arunachal’s Alpine Lakes Face Growing Flood Threat

When you hear the word ‘GLOF’, imagine a mountain‑top lake bursting its natural dam and sending a torrent of water, mud and debris racing downstream. That scary scenario is now a real concern for Arunachal Pradesh, where researchers have identified 38 lakes that could behave that way.

The team, publishing their findings in Discover Hazards, examined 127 lakes across the state. They sorted them into three buckets: 89 low‑risk, 36 medium‑risk and just two high‑risk. The at‑risk lakes are clustered in Upper Dibang Valley, West Kameng and Tawang – regions that host villages, roads and a few hydropower projects.

How did they decide which lake is dangerous? Using the Analytic Hierarchy Process, they weighed things like how fast a lake is expanding, how close it sits to a glacier, and the shape of its surrounding moraine. Expansion rate and glacier proximity turned out to be the biggest tell‑tale signs.

What’s striking is how quickly the high‑altitude lake landscape has changed. Back in 1988, satellite data showed 1,487 lakes covering about 7,922 hectares. Fast‑forward to 2020, and there are 1,985 lakes spread over 11,135 hectares. Most of the new bodies sit between 4,000 and 5,000 m above sea level, a clear sign that the eastern Himalayas are reshaping themselves.

Not all lakes grew the same way. Non‑glacial lakes surged in number and area, while proglacial lakes (the ones directly linked to glaciers) actually dropped a couple in count but swelled in size. Unconnected glacial lakes multiplied, yet their total surface shrank a bit.

Why does this matter? Many of the region’s rivers, including those feeding the mighty Brahmaputra, spring from these basins. Even a “moderate” GLOF could hitch a ride far downstream, dumping sediment, raising water levels quickly and unsettling the river channels.

One of the authors, Nabajit Hazarika from Cotton University, cautions that a disaster on the scale of Nepal’s 2023 floods is unlikely because settlements sit a fair distance from the two high‑risk lakes. Still, distance isn’t the only factor; the speed and volume of water, plus the debris it carries, can still catch downstream communities off‑guard.

The researchers stress that their list is a first pass – there could be other dangerous lakes lurking unseen. They recommend a suite of actions: continuous satellite monitoring, regular hazard reassessments, community‑based early‑warning systems, and protecting critical infrastructure like roads and power stations.

In short, the mountains are sending out a quiet warning. If we listen – and act – we might keep those flash‑flood nightmares at bay.