Nepal flood exposes hydropower risks India cannot ignore

Kathmandu: A catastrophic flash flood that struck Nepal on August 26 has dealt a major blow to the country’s hydropower sector after a huge surge of water, mud and debris swept through the Bhotekoshi and Trishuli river corridors.

The disaster followed a glacier-related collapse and subsequent flooding near the Nepal-Tibet border. Nepal’s technical assessment found that a major surge entered the Bhotekoshi from the Tibetan side before travelling downstream through the Bhotekoshi, Trishuli and Narayani river systems.

The human toll has continued to rise. Reuters reported on September 9 that at least 1,380 people had died and around 5,500 remained missing across Nepal and Tibet. The figures remain subject to search, recovery and identification operations.

The hydropower sector has been among the hardest-hit parts of the infrastructure network. Nepalese reports indicate that at least 13 hydropower projects were affected, including major facilities such as the 216 MW Upper Trishuli-1, 111 MW Rasuwagadhi, 120 MW Rasuwa Bhotekoshi and 60 MW Upper Trishuli 3A projects. Transmission lines, substations and other electricity infrastructure were also damaged.

Initial Nepal Electricity Authority assessments put the electricity disconnected from the national grid at about 431.1 MW. That figure should not be described as 281 MW of operational capacity permanently wiped out without further qualification, because the affected list includes projects with different operating and construction statuses.

The disaster also exposed the dangers facing workers inside large mountain infrastructure projects. Hundreds of workers were initially reported out of contact at hydropower sites, with some believed to be inside tunnels. Reuters reported on September 7 that around 900 hydropower workers were among those missing or unaccounted for, while 121 were believed potentially trapped in tunnel networks. Rescue teams from several countries have been assisting Nepal.

Some underground facilities provided protection, although access to them became extremely difficult after roads, bridges and tunnel entrances were buried or destroyed. In one case, a Chinese worker was rescued from a hydropower tunnel after being trapped for several days.

The disaster has therefore raised a fundamental question for Nepal’s hydropower expansion: how resilient are mountain power projects when floods are substantially larger than the events used in conventional engineering assessments?

Why Nepal’s hydropower model faces a new risk

Nepal has built much of its electricity system around its mountainous rivers, making hydropower central to both domestic electricity supply and its ambitions to export power.

That model has major advantages, particularly because fast-flowing Himalayan rivers provide a large renewable-energy resource. But the same geography exposes power stations, transmission infrastructure, roads and construction sites to landslides, extreme rainfall, debris flows and glacial outburst events.

The August flood demonstrated that the risk is not limited to dams themselves. Powerhouses, substations, transmission lines, access roads and worker accommodation can all become critical points of failure when an entire river corridor is overwhelmed.

The disaster is consequently likely to intensify debate over early-warning systems, geological assessments, tunnel design, emergency evacuation plans and the location of critical electrical equipment.

What it means for India

The consequences extend beyond Nepal because the two countries share river systems, electricity markets and Himalayan geological risks.

India has also provided humanitarian assistance following the disaster. The Ministry of External Affairs said Indian nationals were among those affected and that Indian rescue and specialist teams were assisting Nepal. By early September, Indian officials reported hundreds of Indian nationals missing or uncontactable at different stages of the response, while others had been rescued or had crossed safely into Nepal.

The disaster also matters for India’s downstream flood management. Rivers originating or passing through Nepal eventually feed into major Indian river systems, including the Ganga basin. Indian authorities monitored the situation in Bihar and Uttar Pradesh after the August flooding.

India has its own substantial Himalayan hydropower exposure. Previous disasters, including the 2021 Chamoli disaster and the 2023 South Lhonak glacial lake outburst in Sikkim, have already highlighted the physical risks facing power infrastructure in mountain valleys.

The lesson from Nepal is therefore not that Himalayan hydropower is inherently unviable, but that risk assessment and project design have to account for extreme events that may fall outside historical experience.

India’s hydropower strategy

India continues to expand hydropower alongside solar, wind and other non-fossil sources. The Central Electricity Authority has also published a roadmap for 100 GW of hydro pumped-storage projects by 2035-36, reflecting the growing importance of storage as renewable generation expands.

Pumped storage differs from conventional run-of-river generation because electricity is used to pump water to a higher reservoir during periods of surplus power, with the stored water later released to generate electricity when demand rises.

That makes pumped storage increasingly important for balancing solar and wind generation, but it does not eliminate Himalayan geological risks. Project location, reservoir stability, tunnels, slopes, spillways and access infrastructure still require rigorous assessment.

The Ministry of New and Renewable Energy also continues to support small hydropower development, including a scheme covering projects from 1 MW to 25 MW for 2026-27 to 2030-31.

The bigger Himalayan warning

The Nepal disaster presents a broader infrastructure challenge for both countries.

First, historical flood data may no longer be sufficient. A project designed around past river behaviour can face a very different risk profile if glacier retreat, extreme rainfall and rapid changes in mountain hydrology produce larger events.

Second, protecting generation alone is not enough. Transmission lines, substations, roads and tunnel entrances can become the weakest links. Nepal's experience showed how the destruction of supporting infrastructure can prevent otherwise functioning assets from supplying electricity.

Third, early warning becomes critical. The short time available between an upstream glacial or debris event and downstream flooding means monitoring systems need to detect hazards quickly and communicate warnings to workers and communities.

Fourth, project economics need to include disaster resilience. More robust geological investigations, monitoring systems, emergency access, protected electrical equipment and safer evacuation routes can raise construction costs. However, the Nepal disaster demonstrates the potential cost of underestimating extreme-event risk.

Finally, India and Nepal face a shared Himalayan problem. Electricity trade, river flows, disaster response and infrastructure risks cross national boundaries. The August disaster therefore strengthens the case for greater real-time data sharing, joint flood-warning mechanisms and coordinated planning for infrastructure located along interconnected river basins.

The immediate priority remains rescuing missing people and restoring damaged communities. But once the emergency phase ends, Nepal's hydropower sector is likely to face a much larger strategic question: how can the region continue expanding clean mountain energy without underestimating the physical risks created by a rapidly changing Himalayan environment?