Ong is another important tributary of the Mahanadi River. It rises at an elevation of 457 m on a hill in the northern outskirts of the south-north running Gandhamardan range of mountains situated to the right of the Jonk River. The major tributaries of the river are Chira nalla, Surangi, Utalioe and Khira. The sub-basin lies between north latitudes of 20°41' and 21°29' and east longitudes of 82°33' and 83°50'.The Ong River traverses a total length of about 204 km to join the Mahanadi on its right about 11 km above Sonepur. The drainage area of the Ong River is 5,128 km2 lying in the interior of the main basin. The climate of the Ong basin is mainly dry sub-humid.