Nepal’s deadly flash floods have reignited debate over China’s colossal Medog hydropower project on the Yarlung Tsangpo River in Tibet, with experts warning that the mega-dam could act as a “water bomb” for downstream nations, News18 reported.

The disaster has underscored how fragile Himalayan terrain can unleash sudden cascades of water, ice, rock and debris, raising fears about the risks posed by such massive infrastructure in a seismically volatile region.

At least 165 people were killed in the floods along the Nepal-China border, with hundreds missing after torrents swept through communities, destroyed roads and bridges, and buried buildings under mud. Nepalese police confirmed 157 deaths, while China’s state broadcaster reported three deaths and 265 missing in Tibet’s Gyirong County.

The US Geological Survey initially recorded what seemed to be a magnitude 4.4 earthquake but later revised its assessment, identifying the event as a magnitude 5.2 glacial collapse. Satellite imagery and seismic data confirmed that the trigger was a glacier avalanche, which caused water levels in Nepal’s Trishuli River to rise by nine metres within half an hour.

The same region had suffered a similar disaster in August last year when a glacial lake overflowed in Tibet amid high temperatures, killing nine people and damaging critical infrastructure, including a bridge linking Nepal and China.

These repeated events highlight the vulnerability of Himalayan river systems to sudden glacial hazards, which climate experts say are intensifying as glaciers melt faster under warming conditions.

Strategic affairs expert Brahma Chellaney argued that the Nepal floods demonstrated how even moderate seismic activity in the Himalayas can produce cascading effects, warning that China’s Yarlung Tsangpo mega-dam is a “water bomb in the making.”

He cautioned that the project, located near the Indo-Tibetan border, could drown India’s northeast and wreak havoc downstream in Bangladesh if destabilised by seismic or climatic events. His warning has gained traction because the Nepal disaster illustrated how rapidly hazards can escalate in this region.

The Medog project is being built in southeastern Tibet, where the Yarlung Tsangpo makes a dramatic horseshoe bend and drops nearly 2,000 metres over 50 kilometres.

With an expected installed capacity of 60 gigawatts and annual generation of 300 billion kilowatt-hours, it would be three times larger than China’s Three Gorges Dam. Construction began in 2025, with reports describing it as a five-dam cascade costing around $170 billion.

The river becomes the Brahmaputra after entering India and flows into Bangladesh, meaning the project directly affects two downstream nations.

Concerns are not limited to the dam’s size. Chinese geologists have identified the Paizhen Fault beneath the project site, an active fault line since the Pleistocene. Researchers warned that seismic volatility could destabilise dams, roads, tunnels and reservoirs, urging engineers to strengthen slope stability and introduce retaining protections.

A 2026 report titled The Medog Imperative also highlighted the collision zone of the Indian and Eurasian tectonic plates, warning of landslides and mudflows triggered by earthquakes. Even if the dam itself withstands seismic shocks, secondary geological events could pose grave dangers.

India and Bangladesh are watching closely. Both nations rely on the Brahmaputra for water and sediment flows, and India has raised concerns about downstream impacts.

Experts caution against overstating the dam’s control over the river, noting that much of its eventual volume comes from monsoon rainfall and tributaries south of the Himalayas.

China insists the project is a run-of-the-river system and denies plans to divert water away from downstream countries. Nonetheless, concerns remain over seismic risks, extreme weather, transparency and downstream effects.

The Nepal disaster has amplified calls to reassess how mega-projects are evaluated in the Himalayas, where earthquakes, landslides, glacial hazards and extreme rainfall converge with climate change. Experts note that warming is accelerating glacier melt, steep slopes are unstable, and river valleys are exposed to floods and landslides.

Against this backdrop, Chellaney’s “water bomb” warning has become a stark reminder of the potential consequences of placing the world’s largest hydropower project in one of the planet’s most volatile landscapes.

While the Nepal floods were not caused by the dam, they serve as a chilling example of how fragile Himalayan systems can unleash devastation without warning.

This unfolding debate ties together Himalayan climate fragility, seismic volatility, and the geopolitical anxieties of downstream nations. It highlights the urgent need for transparent risk assessments and regional cooperation before such colossal projects reshape the future of shared river systems.

Agencies