Safety & Advisories

Nepal has 21 glacial lakes scientists rate as dangerous, and here is where they are

A region-wide survey flagged 47 Himalayan lakes as potentially dangerous, 21 of them in Nepal. Where they are, and what they mean for your trek.

By Laxman Rawal · Aug 31, 2026

Every trekker who has stood in Dingboche and looked up the side valley toward Island Peak has walked within a few kilometres of Imja Tsho. It barely existed a century ago — it was a scatter of meltwater ponds on the Imja Glacier. Today it is over a kilometre…

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How a glacial lake bursts

The mechanism is simple and the physics are not forgiving. As glaciers retreat, they leave lakes dammed only by loose piles of rock and ice debris called moraine — not bedrock. An avalanche, a landslide, or even a chunk of hanging glacier calving into the…

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What the last two monsoons showed

The last two monsoons put the theory back on front pages. In July 2025, ICIMOD's own analysis attributed a destructive flood on the Bhote Koshi river to the sudden collapse of a superglacial lake on a glacier across the border in Tibet — a textbook GLOF…

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The lakes on the watch list

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What Nepal has done about it

Nepal has not ignored the problem. In 2000, engineers cut a 70-metre canal into Tsho Rolpa's moraine dam and lowered the lake by three metres — an operation that, at the time, was one of the highest-altitude engineering projects on Earth. In 2016, a joint…

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What this means for trekkers

What this means for you A dangerous lake is not a reason to cancel an Everest or Annapurna region trek — the risk is specific to particular valleys, not the whole Himalaya, and none of the watch-listed lakes sit directly on the standard trekking trails to…

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