38 Arunachal Lakes Face Medium‑to‑High Glacial Lake Outburst Flood Risk, Study Warns

Scientists have sounded the alarm over a growing threat in Arunachal Pradesh: out of more than a hundred high‑altitude lakes, 38 are now deemed either medium or high risk for a glacial lake outburst flood, commonly called a GLOF.

The research, published in the journal Discover Hazards, examined 127 lakes across the state. While 89 fell into a low‑risk category, 36 were labelled medium‑risk and just two crossed the line into high‑risk territory. All of the more vulnerable lakes cluster in the Upper Dibang Valley, West Kameng and Tawang districts – regions that host downstream villages, vital hydropower projects and the headwaters of the Brahmaputra.

So, what exactly is a GLOF? In simple terms, it’s a sudden, often violent release of water stored in a glacial or high‑altitude lake, usually triggered when a natural moraine dam gives way. The deluge can carry rocks, sediment and debris far downstream, wreaking havoc well beyond the lake’s immediate surroundings.

The numbers behind the threat are striking. Using satellite images spanning three decades, the team tracked a noticeable rise in both the count and total surface area of lakes in the region. Back in 1988, Arunachal Pradesh boasted 1,487 mapped lakes covering roughly 7,922 hectares. Fast forward to 2020, and that tally jumped to 1,985 lakes and about 11,135 hectares.

Most of the growth came from non‑glacial lakes – their numbers swelled by 498 and their combined area expanded by over 3,200 hectares. Glacial lakes showed mixed trends. Proglacial lakes (directly attached to glaciers) actually shrank in number from 24 to 22, yet their total area grew from 111 to 126 hectares. Unconnected glacial lakes, on the other hand, increased in count (136 to 205) but shrank in overall size, dropping from 1,364 to 1,216 hectares.

Why the shift? The researchers point to warming temperatures, retreating glaciers and broader climate‑change dynamics. As glaciers melt, new basins can appear and existing ones can expand, setting the stage for potential outbursts. “Many rivers spring from these high‑altitude basins and feed the Brahmaputra,” the study notes, warning that even a modest GLOF could travel long distances, dumping sediment and destabilising river channels downstream.

Lead author Nabajit Hazarika of Cotton University cautions that a disaster on the scale of Nepal’s 2023 floods is unlikely in Arunachal, simply because populated areas sit relatively far from the identified high‑risk lakes. Still, he stresses that distance alone doesn’t guarantee safety – the speed and volume of water, mud and rock can surge quickly, raising river levels downstream in a matter of hours.

The paper ends with a clear set of recommendations: continuous lake monitoring (preferably via satellite and ground‑based sensors), regular updates to hazard maps, and the rollout of early‑warning systems that can alert communities in time. Community awareness programmes, protection of critical infrastructure and coordinated disaster‑response planning are also urged.

In short, the mountains are changing, and with them the risk landscape. Keeping a watchful eye on these expanding lakes could make the difference between a manageable flood and a catastrophe.