RIVERS IN NEPAL

Nepal has three categories of rivers. The largest systems -— from east to west Koshi, Gandaki/Narayani, Karnali/Goghra and Mahakali -- originate in multiple tributaries rising in or beyond the high Himalaya that maintain substantial flows from snowmelt through the hot, droughty spring before the summer monsoon. These tributaries cross the highest mountains in deep gorges, flow south through the Middle Hills, then join in candelabra-like configuration before crossing the Mahabharat Range and emerging onto the plains where they have deposited megafans exceeding 10,000 km2 (3,861 sq mi) area.
The Koshi is also called Sapta Koshi for its seven Himalayan tributaries in eastern Nepal: Indrawati, Sun Koshi, Tama Koshi, Dudh Koshi, Liku, Arun, and Tamur. The Arun rises in Tibet some 150 km. beyond Nepal's northern border. A tributary of the Sun Koshi, Bhote Koshi also rises in Tibet and is followed by the Arniko Highway connecting Kathmandu and Lhasa.