major left-bank tributary of the Ganges River, rising as the Karnāli River (Chinese: K'ung-ch'iao Ho) in the Tibetan Himalayas and flowing southeast into Nepal. Cutting southward across the Siwālik Hills, it splits into two branches, to rejoin south of the Indian border and form the Ghāghara proper. It flows southeast through Uttar Pradesh and Bihār states to enter the Ganges below Chāpra after a 600-mile (970-kilometre) course. The major tributaries—the Kuwānā, the Rāpti, and the Little Gandak rivers—all flow into the Ghāghara from the mountains to the north. Together with the Ganges and its tributaries, it has helped form the vast alluvial plain of northern Bihār. Along its lower course it is also called the Sarju River (the Sarabos of the 2nd-century-AD Greek geographer Ptolemy) and the Deoha.