Karnali

The Karnali (Tibetan: Mapcha Tsangpo, often rendered Mapcha Khambab, the "Peacock River") is the longest river entirely associated with Nepal, running about 507 km (315 mi) within the country and roughly 1,080 km (670 mi) in total before its waters reach the Ganges. It rises on the northern slopes of the Himalaya on the Tibetan Plateau, in the broader Lake Manasarovar–Mount Kailash region from which several of Asia's great rivers descend, fed by glacial meltwater at high elevation.

The headwaters form two principal arms in Nepal's remote far-northwest. The Humla Karnali enters from Tibet through Humla district, while the Mugu Karnali drains the high country to the east; the two converge near Galwa, and together with the Tila River build the main stem of the Upper Karnali. The river then carves deep, antecedent gorges southward through the rugged districts of Karnali Province — Humla, Mugu, Jumla, Kalikot, Dolpa and others — having cut its valley faster than the mountains rose around it.

Below the mountains the Karnali crosses the Mahabharat Range and the Siwalik (Churia) Hills near Chisapani, where it emerges onto the plains and splits into two main braided channels, the Geruwa and the Kauriala, which embrace the western part of Bardia National Park before rejoining south of the Nepal–India border. In India the river is known as the Ghaghara (and, in its lower Awadh reaches, the Sarayu), and it ultimately joins the Ganges in Bihar, making the Karnali–Ghaghara the largest tributary of the Ganges by volume.

The Karnali basin is one of the largest in the Himalaya, with a total catchment on the order of 127,950 sq km (about 49,400 sq mi) by the time the river reaches the Ganges; more than 90% of the basin within Nepal lies upstream of the gauging station at Chisapani, the river's principal hydrological reference point. Mean annual flow at Chisapani is on the order of 1,389–1,392 cubic metres per second.

The river is fed by a heavily glacierised, snow-rich headwater region; studies of the basin count well over a thousand glaciers and hundreds of glacial lakes, and snowmelt plays a significant role in sustaining flows and buffering dry-season droughts. Flow is strongly seasonal, peaking during the summer monsoon and falling sharply in the dry months.

Two large tributaries dominate the lower system. The Bheri River, about 264 km long, rises in the western Dhaulagiri Himalaya and drains the eastern part of the catchment, joining the Karnali in the Surkhet area; the Seti (West Seti) River, about 202 km long, drains the western catchment and enters from the north. The remainder of the river's flow is supplied by the snow-fed upper tributaries including the Mugu Karnali, Humla Karnali and Tila.

The Karnali's large, steady flow and steep Himalayan gradient give it some of the greatest untapped hydropower potential in South Asia. The flagship proposal is the Karnali (Chisapani) Multipurpose Project, sited around the gorge near Chisapani in the Kailali–Bardiya area. First studied as a smaller scheme by Japan's Nippon Koei in the 1960s, feasibility work by 1989 identified a potential installed capacity of about 10,800 MW — which would make it one of the largest hydropower projects on the subcontinent.

As envisaged in feasibility studies, the project would impound the Karnali behind a rock-fill dam roughly 270 m high, routing water through tunnels and penstocks to an underground powerhouse with multiple turbines. Beyond power, it is conceived as a multipurpose storage scheme offering downstream irrigation across large areas of farmland in Nepal's Terai and northern India, along with flood regulation.

Despite decades of study, the scheme has not been built, and the Nepalese government has repeatedly revived planning, including efforts to commission detailed engineering studies and financing arrangements. Because so little of the Karnali is currently dammed, it remains a major focus of debate over Nepal's energy-export ambitions versus the value of a largely intact river.

The Karnali is woven into Hindu and Buddhist sacred geography through its association with the Kailash–Manasarovar region of Tibet, a place revered by Hindus, Buddhists, Jains and followers of Bon. The area around Mount Kailash and Lake Manasarovar is traditionally regarded as the source region of several holy rivers, and the Karnali is counted among the great waters linked to this sacred landscape.

The Tibetan name Mapcha Khambab, often rendered as the "Peacock River," reflects mythic traditions in which each of the major rivers issuing from the Kailash–Manasarovar mandala is associated with an animal-mouthed source. These traditions tie the river's headwaters to one of the most important pilgrimage centres in the Himalaya.

Downstream, the river's Indian continuation carries deep religious resonance: as the Ghaghara and especially as the Sarayu, it is the river associated with Ayodhya in the Ramayana, central to the story of Rama. The river thus connects a remote, sparsely populated Himalayan headwater to some of the most storied sacred sites of the wider Ganges plain.

The Karnali is frequently described as Nepal's last major free-flowing river, a status that underpins its exceptional ecological value. Its lower reaches and the braided Geruwa channel support endangered Ganges river dolphins and gharial crocodiles, and the river sustains a rich fish fauna; periodic natural flooding is important for the wetland-dependent species and floodplain habitats of the region.

The Karnali is the lifeline of Bardia National Park, the largest protected area in the lowland part of the basin, whose forests and grasslands shelter tigers, one-horned rhinoceros, elephants, deer and abundant birdlife. The river is also internationally known among paddlers for multi-day white-water expeditions through its remote gorges, with rapids spanning roughly Class II to Class V, an activity that has become an economic and conservation argument for keeping the river undammed.

The basin faces significant natural hazards. As a high, heavily glacierised Himalayan catchment, it is exposed to glacial lake outburst floods and to intense monsoon flooding, while the far-western region is regarded as among the most vulnerable in Nepal to climate change. Large-scale damming proposals such as Karnali (Chisapani) raise additional environmental concerns over altered flood regimes, sediment transport, fish migration and habitat for the river's threatened megafauna.