Mahanadi River System

The Mahanadi, meaning "the great river", is one of the major east-flowing rivers of peninsular India. It rises in the hills of Chhattisgarh, flows east through Odisha, and falls into the Bay of Bengal. Its basin covers about 1,41,589 sq km, which is nearly 4.3% of India's land area. It is the lifeline of central Chhattisgarh's rice plains and of Odisha's coastal delta.

Where does it start and end?

The Mahanadi starts in the Sihawa hills of Dhamtari district in Chhattisgarh. It flows about 851 km in total. It first runs north, then turns east through the Chhattisgarh plains, enters Odisha, and passes through the Hirakud reservoir near Sambalpur. Further down, it cuts through the Eastern Ghats in the Satkosia gorge and then spreads into a wide delta near Cuttack. It finally enters the Bay of Bengal near False Point, close to the port of Paradip.

How is the basin shared?

The Mahanadi basin lies mainly in two states:

• Chhattisgarh: about 75,858 sq km (roughly 53% of the basin)
• Odisha: about 65,580 sq km (roughly 46%)
• Small parts lie in Jharkhand (old Bihar area) and Maharashtra, and some sources also list a small area in Madhya Pradesh.

This split is the root of the dispute. Chhattisgarh holds more of the catchment, but Odisha, downstream, has the big dam and the densely populated delta.

The main tributaries

A tributary is a smaller river that joins a bigger one.

• Left bank (joining from the north): Seonath, Hasdeo, Mand and Ib
• Right bank (joining from the south): Ong, Tel and Jonk

The Seonath is the longest tributary and drains about 22% of the basin. The Seonath, Ib and Tel together cover nearly 47% of the whole catchment. A simple memory trick: the big ones are "S-I-T" (Seonath, Ib, Tel).

Hirakud Dam: the heart of the system

The Hirakud Dam stands on the Mahanadi about 15 km from Sambalpur in Odisha. Work began in 1948, and Prime Minister Jawaharlal Nehru dedicated it to the nation on 13 January 1957. It was one of independent India's first major multipurpose river valley projects: it controls floods, irrigates fields, and produces electricity.

• The main dam is about 4.8 km long. With the earthen dykes (long walls of earth) on both sides, the total length is about 25.8 km, making it one of the longest earthen dams in the world.
• Before the dam, the Mahanadi delta suffered frequent, severe floods. The dam was built mainly to control these floods.
• The Hirakud Reservoir was declared a Ramsar site (a wetland of international importance) on 12 October 2021.

The delta and Chilika

Below Cuttack, the river splits into many branches, called distributaries, forming one of India's largest deltas. Its southern branches, mainly the Daya and Bhargavi, carry much of the fresh water that flows into Chilika Lake, Asia's largest brackish-water lagoon (a lake that is a mix of sea water and river water). So the Mahanadi's flow also shapes Chilika's ecology.

Other features worth knowing

• Satkosia gorge: a gorge about 22 km long where the Mahanadi cuts through the Eastern Ghats. It is part of the Satkosia Tiger Reserve (notified 2007) and was also made a Ramsar site in 2021.
• Minerals and industry: The basin has large coal reserves, such as the Ib Valley coalfield, and many thermal power plants and steel units. These industries need a lot of water, which adds to the demand.
• Rice bowl: The Chhattisgarh plains in the upper basin are known as the "rice bowl of central India".

How the dispute arose

For many years, Odisha has said that Chhattisgarh's barrages (low dams that hold back water) and other projects on the upper Mahanadi and its tributaries reduce the water reaching Hirakud, especially in the non-monsoon months. Chhattisgarh says it is using water within its fair share and needs it for its farmers, industries and tribal areas.

• In 2016, Odisha filed a complaint with the Centre under Section 3 of the Inter-State River Water Disputes Act, objecting mainly to barrages built for industrial use.
• In January 2018, the Supreme Court directed the Centre to set up a tribunal within a month.
• On 12 March 2018, the Centre set up the Mahanadi Water Disputes Tribunal. It was first headed by Justice A.M. Khanwilkar. After he resigned in 2024, Justice Bela M. Trivedi was appointed chairperson.
• The tribunal's term has been extended several times. In April 2026, it was extended up to 13 January 2027.

Commonly confused concepts

• Mahanadi vs Brahmani and Baitarani: All three are east-flowing rivers of Odisha with neighbouring deltas. The Bhitarkanika mangroves lie in the Brahmani-Baitarani delta, not the Mahanadi delta.
• Hirakud vs Bhakra Nangal: Hirakud (on the Mahanadi, Odisha) is famous for its length as an earthen dam. Bhakra (on the Sutlej, Himachal Pradesh-Punjab border) is famous for its height as a concrete gravity dam.
• Mahanadi vs Godavari basin: The Godavari basin is larger and is the largest river basin of peninsular India. The Mahanadi basin is smaller but still among the major ones.
• Distributary vs tributary: A tributary joins the main river and adds water to it. A distributary breaks away from the main river, usually in a delta, and carries water away from it.

Issues, criticism and the way forward

• Low-flow season stress: Most of the river's water comes during the monsoon. In the dry months, demand from farms, cities and industries is high, and the flow is low. This is when disputes become sharp.
• Industrial demand: Coal mines, thermal plants and steel units in both states compete with irrigation for the same water.
• Floods still occur: In very heavy rain years, the delta still faces floods, and the operation of Hirakud's gates becomes a key issue.
• Data gaps: The two states have often presented different figures on water availability. Joint, scientific measurement is the base for any fair agreement.
• Way forward: Experts suggest joint basin-level planning, shared real-time flow data, water-saving irrigation, and agreed release rules in the lean season, so that both states benefit.

Concepts to Know

• River basin (catchment): The whole area of land from which rain water flows into a river and its tributaries.
• Barrage: A low dam with many gates that holds back river water to raise its level for canals, without storing a very large amount like a big dam.
• Multipurpose project: A dam project that serves several goals at once, such as flood control, irrigation, electricity and drinking water.
• Delta: A low, flat area of land formed where a river deposits mud and sand as it spreads into many branches before meeting the sea.
• Ramsar site: A wetland declared to be of international importance under the Ramsar Convention, 1971, an international treaty to protect wetlands.
• Brackish water: Water that is saltier than river water but less salty than sea water.