Glacial Lakes and Flood Risk in the Hindu Kush–Himalaya ^{CEFR B2}

The Hindu Kush–Himalaya, often called the “Third Pole,” is losing ice as global temperatures rise, and scientists estimate up to 75 percent of the region’s glacier volume could vanish by the end of the century. As glaciers retreat, meltwater accumulates in new glacial lakes; these lakes can accelerate ice loss and grow over time. Since 1990 glacial lakes worldwide have expanded by roughly 53 percent in number, 51 percent in surface area and 48 percent in volume.

Glacial lakes help feed major rivers such as the Indus and the Brahmaputra, but they can fail suddenly and cause Glacial Lake Outburst Floods (GLOFs). The HKH and High Mountain Asia have the highest global GLOF exposure: about 9.3 million people at risk, which is roughly 62 percent of the globally exposed population. Of the most affected populous countries, India, Pakistan and China are in the HKH, and India and Pakistan are rated as having the highest GLOF danger worldwide.

Researchers have recorded over 500 GLOF events across the HKH. Notable recent disasters include the 2013 Chorabari flood in India and the 2023 South Lhonak outburst in Sikkim, where a 14.7 million cubic meter permafrost slide into South Lhonak Lake at 5,200 meters generated a 20‑meter impact wave, breached the dam and released 50 million cubic meters of water. The resulting flood carried about 270 million cubic meters of sediment and debris, cut a 385‑kilometer path along the Teesta River to Bangladesh, caused 55 deaths, displaced thousands and destroyed roads, buildings and dams including the Teesta III hydropower dam.

Other events show risks to development: a 2020 GLOF at Jinwuco, China released an estimated 10 million cubic meters of water and damaged villages and 382.43 mu (25.5 hectares) of farmland. In 1985 a glacier lake flood destroyed the nearly completed Namche Small Hydropower Plant, costing Nepal about USD 1.5 million and delaying local energy access. Experts note that GLOFs are hard to predict because triggers vary locally. Zhang Qianggong warns a single event can trigger landslides affecting areas within 10 kilometers, and Wang Shijin links warming to increased cryosphere instability. Xu Baiqing stresses international cooperation; his institute and European partners compiled a glacier lake inventory using space‑air‑ground observations. Current risk assessment concentrates on water volume, moraine stability and potential downstream damage, and for high‑risk sites recommends observation, early warning systems and preventive infrastructure, all of which depend on good data.