The longest river flowing through the heart of Odisha is Mahanadi. Also it is a major river in East Central India. It is the sixth largest river in India. It is 857kms long (494kms in Odisha) and its catchment area spreads over 141,600 sq kms (65,580 sq kms in Odisha). The river flows through the states of Chhattisgarh and Odisha.
The river carries on an average about 92,600 million of water. It originates from the Maipal range in Chhattisgarh popularly known as the Amarkantak plateau. It is joined by the Jonk and Hasdeo rivers here before entering into Odisha after covering about half of its total length. Then it enters the north west of modern Odisha in the Sambalpur district near padigan, a little above Hirakud. At Hirakud the longest dam in the world has been built across the river. A composite structure of earth, concrete and masonry, the dam measures 24 km including the Dykes. It spans two hills; the Lamdungri on the left and the Chandili Dunguri on the right. It also forms the biggest artificial lake in Asia, with a reservoir holding 743 sq km at full capacity, with a shoreline of over 640 km.
The river enters the Odisha plains at Naraj, about 11 km from Cuttack, where it pours down between two hills that are a mile apart. A barrage has been constructed here to regulate the river’s flow into Cuttack. Just before entering Cuttack, it gives off a large distributary called the Kathjori. The city of Cuttack stands on the spit separating the two channels. The Kathjori then throws off many streams like the Kuakhai, Devi and Surua which fall into the Bay of Bengal after entering Puri district. The Kathjori itself falls into the sea as the Jotdar. Other distributaries of Mahanadi include the Paika, Birupa, Chitroptala river, Genguti and Lun. The Birupa then goes on to join the Brahmani River at Krushnanagar and enters the Bay of Bengal at Dhamra. The Mahanadi proper enters the sea via several channels near Paradeep at False Point, Jagatsinghpur. The combined Delta of the Mahanadi’s numerous distributaries and the Brahmani is one of the largest in India.
The Mahanadi is an important river in the state of Odisha. This river flows slowly for about 900 km and deposits more silt than any other river in the Indian subcontinent. However today the Mahanadi valley is best known for its fertile soil and flourishing agriculture. The Mahanadi was notorious for its devastating floods for much of recorded history. However the construction of the Hirakud Dam has greatly altered the situation. Today a network of canals, barrages and check dams keep the river well in control.