Kali Gandaki

The Kali Gandaki rises from the Nhubine Himal glacier in Upper Mustang, at 6,268 m near the Tibet border, and flows south through the old walled kingdom of Lo as a braided grey river in a vast arid valley — the upper reach known as the Thak Khola. Past Kagbeni and Jomsom it slips directly between Dhaulagiri (8,167 m) and Annapurna I (8,091 m).

There it performs its famous feat: about 7 km downstream of Tukuche the riverbed lies at 2,520 m — a full 5,571 m below the summit of Annapurna I — making the Kali Gandaki gorge, by the summit-to-river measure, the deepest in the world. The gorge has been a trans-Himalayan trade corridor for centuries, the route by which Tibetan salt came south, and the Thakali people of the valley grew prosperous on that trade.

The river is equally important to the sacred geography of Hinduism. Its black gravels yield shaligram stones — ammonite fossils revered as one of the non-living forms of Vishnu — found almost nowhere else, and the dark river itself is identified with the goddess Kali.

Lower down, the river turns industrious. The 144 MW Kaligandaki A at Mirmi in Syangja — commissioned in 2002 with Asian Development Bank backing at a cost of US$354.8 million — was Nepal's largest power plant until Upper Tamakoshi, and wrestles with one of the world's toughest sediment regimes: the river delivers around 43 million tonnes of suspended sediment a year, 95% of it in the monsoon, managed by carefully timed reservoir sluicing. The middle reaches are also a popular rafting river.