The Sone is a perennial river that rises in the Amarkantak hills of Madhya Pradesh, runs about 784 km through Madhya Pradesh, Chhattisgarh, Uttar Pradesh, Jharkhand and Bihar, and joins the Ganga near Koilwar, upstream of Patna. It is one of the largest of the Ganga's southern, or right-bank, tributaries, and the Sone canal system it feeds is among the oldest irrigation networks in eastern India. Its waters were formally apportioned on 16 September 1973, when Madhya Pradesh, Uttar Pradesh and undivided Bihar signed the Bansagar Agreement, dividing 14.25 MAF between them and settling how the cost of the Bansagar Dam would be shared. The arrangement held for 27 years. When Jharkhand was carved out of southern Bihar in November 2000, the 7.75 MAF that the 1973 pact had assigned to undivided Bihar suddenly belonged to two states with no formula to split it between them, and the successor states could agree on neither the quantum nor the drawing points. The stalemate blocked planning on the Sone canal system and on irrigation in the Palamu-Garhwa belt of Jharkhand for a quarter of a century. What broke it was not adjudication but negotiation: the Ministry of Jal Shakti put a Central Water Commission-chaired committee on the technical questions, and the political question was taken to the Eastern Zonal Council, whose Ranchi meeting on 10 July 2025 produced the framework the two Chief Ministers eventually signed in Delhi.

The significant thing about this settlement is the route it took. India's standard answer to an inter-State river dispute is a tribunal under the 1956 Act, and the standard complaint about that answer is that tribunals take decades and their awards are themselves litigated. The Sone dispute went the other way: a technical committee under the Central Water Commission to establish what the river could actually deliver, and the Eastern Zonal Council, chaired by the Union Home Minister, to carry the political bargain. That is the executive federal machinery working as designed, and it is the framing an examiner is most likely to test - Zonal Councils as statutory instruments of cooperative federalism, as against the constitutional Inter-State Council under Article 263 and the adjudicatory route under Article 262. The second point worth holding on to is that the pact created nothing new. It divided a 1973 entitlement between two states that had been one state when the entitlement was granted, which is why the arithmetic closes exactly: 5.75 plus 2.0 equals the 7.75 MAF undivided Bihar was given at Bansagar. The practical stake is irrigation and drinking water across eight districts of the Bihar plains and the Palamu-Garhwa belt of Jharkhand, a chronically water-short region where the absence of an agreed share had frozen project planning for 25 years.