Nepal floods expose shared Himalayan river risk for India

September 3, 2026 at 05:58 AM2 min

This digest was compiled by AI from multiple sources — links to the originals are below.

Nepal's devastating floods, which have killed over 1,000 people, have exposed a transboundary risk that extends into India. The two countries share a vast Himalayan river system, with more than 6,000 rivers and streams flowing from Nepal into India. Bihar is the most exposed Indian state, with roughly three-quarters of north Bihar classified as flood-prone.

Key Facts

Nepal has more than 6,000 rivers and streams, most draining south into India and the Ganges.
Bihar is India's most flood-prone state, with roughly three-quarters of north Bihar officially classified as flood-prone.
The Kosi, Gandaki (Gandak), and Karnali (Ghaghara) are the three major river systems flowing from Nepal into India.
Eastern Uttar Pradesh is vulnerable to the Ghaghara, Rapti, and Gandak rivers, with districts like Gorakhpur and Bahraich regularly affected.

Transboundary River Systems

Nepal has more than 6,000 rivers and streams, most draining south into India and the Ganges. Three major systems dominate: the Kosi in the east, the Gandaki (Gandak in India) in the centre, and the Karnali (Ghaghara in India) in the west, with the Mahakali (Sharda) along the western border. A dozen smaller rivers rising in the Siwaliks and Chure—including the Bagmati, Kamala, Rapti, and Babai—are less famous but can produce faster, more unpredictable floods because their catchments are small and steep. Seven to nine major rivers flow from Nepal into the Indian plains, and they are responsible for flooding in India, according to Manish Shrestha, a hydrologist at the International Centre for Integrated Mountain Development (ICIMOD). India's Central Water Commission identifies the Kosi, Gandak, Bagmati, and Ghaghara as some of the main transboundary rivers.

Indian States at Risk

Bihar is by far the most exposed Indian state, with roughly three-quarters of north Bihar officially classified as flood-prone. Almost all the major rivers that flood the state originate in Nepal, with the Kosi—the 'sorrow of Bihar'—the most notorious, followed by the Gandak, Bagmati, and Kamala. Eastern Uttar Pradesh is vulnerable to the Ghaghara, Rapti, and Gandak rivers, with districts like Gorakhpur, Bahraich, Lakhimpur Kheri, and Shravasti regularly affected. Uttarakhand state shares the Mahakali-Sharda rivers, and North Bengal receives the Mechi and Mahananda. Bihar dominates in scale, while Uttar Pradesh is second and often under-reported, according to Pradeep Man Dangol, hydrologist at ICIMOD.