The Sone River is an important right bank tributary of the Ganga River. The river originates at an elevation of 600 m at Sonbhadra in the Maikala range of hills in Madhya Pradesh. The total catchment area of the basin is 71,259 sq. km. The important tributaries of the Sone River are Rihand, Kanhar, Ghaghar, and Koel. The Rihand dam has been constructed on the Rihand River. The total length of the river is 784 km, out of which about 500 km lies in Madhya Pradesh, 82 km in Uttar Pradesh and the remaining 202 km in Bihar. The river meets the Ganga River about 16 km upstream of Dinapur in the Patna district of Bihar.