The Kali Gandaki or Gandaki River (also known as the Narayani in southern Nepal and the Gandak in India) is one of the major rivers of Nepal and a left bank tributary of the Ganges in India. It is also called Krishna Gandaki in Nepal. In Nepal the river is notable for its deep gorge through the Himalayas and its enormous hydroelectric potential. It has a total catchment area of 46,300 square kilometers (17,900 sq mi), most of it in Nepal. The basin also contains three of the world’s 14 mountains over 8,000m, Dhaulagiri, Manaslu and Annapurna I. Dhaulagiri is the highest point of the Gandaki basin. It lies between the similar Kosi system to the east and the Karnali (Ghaghara) system to the west.
The Kali Gandaki river source is at the border with Tibet at an altitude of 6,268 m (20,564 ft) at the Nhubine Himal Glacier in the Mustang region of Nepal.
The headwaters stream on some maps is named the Chhuama Khola and then, nearing Lo Manthang, the Nhichung Khola or Choro Khola. The Kali Gandaki then flows southwest (with the name of Mustang Khola on old, outdated maps) through a sheer-sided, deep canyon before widening at the steel footbridge at Chele, where part of its flow funnels through a rock tunnel, and from this point the now wide river is called the Kali Gandaki on all maps. In Kagbeni a major tributary named Johng Khola, Kak Khola or Krishnaa descends from Muktinath.
The river then flows southward through a steep gorge known as the Kali Gandaki Gorge, or Andha Galchi, between the mountains Dhaulagiri (8167 m) to the west and Annapurna I (8091 m) to the east. If one measures the depth of a canyon by the difference between the river height and the heights of the highest peaks on either side, this gorge is the world’s deepest. The portion of the river directly between Dhaulagiri and Annapurna I (7 km downstream from Tukuche) is at an elevation of 2520 metres, 5571 metres lower than Annapurna I. The river is older than the Himalayas. As tectonic activity forces the mountains higher, the river has cut through the uplift.
South of the gorge, the river is joined by Rahughat Khola at Galeshwor, Myagdi Khola at Beni, Modi Khola near Kushma and Badigaad at Rudrabeni above Ridi Bazaar. The river then turns east to run along the northern edge of the Mahabharat Range. The largest hydroelectricity project in Nepal is located along this stretch of the river. Turning south again and breaking through the Mahabharats, Kali Gandaki is then joined by a major tributary, the Trishuli, at Devighat, then by the East Rapti River draining the Inner Terai valley known as Chitwan. The Gandaki then crosses the outermost foothills of the Himalayas—Sivalik Hills—into the Terai plains of Nepal. From Devighat, the river flows southwest of Gaindakot town. The river later curves back towards the southeast as it enters India where it is called the Gandak.
Below Gaindakot the river is known as the Narayani or Sapt Gandaki (Seven Gandakis), for seven tributaries rising in the Himalaya or further north along the main Ganges-Brahmaputra divide. These are the Kali Gandaki, the Trishuli River, and the five main tributaries of the Trishuli known as the Daraudi, Seti, Madi, Marsyandi and Budhi.