The Gomati river originates in the foothills of the Himalayas and flows through Uttar Pradesh, joining the Ganga near Saidpur. West of the Gomati's confluence, the Ghaghara (also known as Saryu) river, a major Himalayan tributary, joins the Ganga. Further east of the Ghaghara's confluence, the Gandak river merges with the Ganga. The Kosi river, known as the 'Sorrow of Bihar', is the easternmost of these four major tributaries, joining the Ganga in Bihar.