Explanation: Karmanasha, Gandak and Ghaghra rivers form the boundary between Uttar Pradesh and Bihar. Ghaghara river, is a major left-bank tributary of the Ganges river. It rises as the Karnali river in the high Himalayas of southern Tibet Autonomous Region, China, and flows southeast through Nepal. Cutting southward across the Siwalik Range, it splits into two branches that rejoin south of the Indian border and form the Ghaghara proper. It flows southeast through Uttar Pradesh and Bihar states to enter the Ganges below Chapra after a 600 -mile course. Gandak river, also called Narayani River, river in central Nepal and northern India. It is formed by the union of the Kali and Trisuli rivers, which rise in the Great Himalaya Range in Nepal; from this junction to the Indian border the river is called the Narayani. It flows southwest into India and then turns southeast along the Uttar Pradesh-Bihar state border and across the Indo-Gangetic Plain. It enters the Ganges (Ganga) river opposite Patna after a winding course of 475 miles . The Karmanasa originates at a height of 350 metres (1,150 ft) on the northern face of Kaimur Range near Sarodag in Kaimur district of Bihar.