Mahakali (Sharda)

The Mahakali — the Kali of Kumaon, the Sharda of the Indian plains — runs the length of Nepal's western border. Even its source is contested: one headstream rises near Kalapani below the Lipu Lekh pass at over 5,500 m, another in India's Pithoragarh district, and the question of whether the true Mahakali begins at Lipu Lekh or further west at Limpiyadhura sits at the centre of the Kalapani territorial dispute between Nepal and India. From Darchula southward the river itself is the boundary, with twin towns facing each other across the water.

It is a powerful, flashy Himalayan river: across its ≈14,871 km² basin the mean flow is about 730 m³/s, but the seasonal swing runs from around 150 m³/s in March to 1,580 m³/s in July. Nepal's tributaries include the Chameliya, which carries a hydropower plant of its own.

No river in Nepal is more thoroughly wrapped in treaty law. The Sharada Barrage at the border — its headworks date to 1928 — and India's Tanakpur Barrage (commissioned 1993, 120 MW) both draw on the river, and the Mahakali Treaty signed on 12 February 1996 consolidated the arrangements: Nepal is entitled to 28.35 m³/s of water in the wet season and 4.25 m³/s in the dry, plus a share of Tanakpur's energy, and the river is recognised as a boundary river to be developed jointly. The Mahakali Irrigation Project, a National Pride Project, waters Kanchanpur and Kailali from the barrage.

The treaty's centrepiece remains unbuilt: the Pancheshwar Multipurpose Project, a 293 m rockfill dam — it would be among the world's tallest — with an installed capacity discussed at 5,600–6,480 MW shared equally between the two countries, plus a re-regulating dam downstream. Three decades after the treaty, the detailed project report is still being negotiated, making Pancheshwar South Asia's most consequential unbuilt dam.