MAHANADI ("The Great River"), river, India. It rises in 2o° 1o' N., 82° E., 25 m. S. of Raipur town, in the wild mountains of Bastar in the Central Provinces. At first an insig nificant stream, taking a northerly direction, it drains the eastern portion of the Chhattisgarh plain, then a little above Seorinarayan it receives its first great affluent, the Seonath; thence flowing for some distance due E., its stream is augmented by the drainage of the hills of Uprora, Korba, and the ranges that separate Sambal pur from Chota Nagpur. At Padampur it turns towards the south, and struggling through masses of rock, flows past the town of Sambalpur to Sonpur. From Sonpur it pursues a tortuous course among ridges and rocky crags towards the range of the Eastern Ghats, which it pierces by a gorge overlooked by forest-clad hills. Since the opening of the Bengal-Nagpur railway, the Mahanadi is little used for navigation. It reaches the Orissa delta at Naraj, about 7 m. west of Cuttack town ; and after traversing Cuttack district from west to east, and throwing off numerous branches, it falls into the Bay of Bengal at False point by several channels.
The Mahanadi has an estimated drainage area of 50,000 sq.m., and its rapid flow renders its maximum discharge in time of flood second to that of no other river in India. During high floods over 1,500,000 cu.ft. of water pour every second through the Naraj gorge. In the dry weather the discharge dwindles to Soo cu.ft. per second in a normal year. Efforts have been made to husband and utilize the vast water supply thrown upon the Orissa delta during seasons of flood. Each of the three branches into which the parent stream splits at the delta head is regulated by a weir. The four canals which form the Orissa irrigation system irrigate 292,000 acres. Two take off from the Biropa weir, and one, with its branch, from the Mahanadi weir. A new canal to protect the Raipur district, with headworks at Rudri on the Mahanadi, which was in course of construction in 1926, will irrigate a further 300, 000 ac. when completed.