PATNA, Sept. 1 -- The long-pending Indrapuri reservoir project on Sone river is set to get a fresh lease of life after the formalisation of the river's water-sharing agreement between Bihar and Jharkhand in New Delhi on Monday in the presence of Union home minister Amit Shah, Bihar chief minister Samrat Choudhary, his Jharkhand counterpart Hemant Soren and union Jal Shakti minister C R Patil. The pact, which allocates 5.75 million acre-feet (MAF) of Sone water to Bihar and 2 MAF to Jharkhand from the original undivided Bihar entitlement of 7.75 MAF under the 1973 Bansagar Agreement, removes the principal interstate obstacle that had kept the multipurpose scheme on hold for decades. Bihar officials said a fresh detailed project report (DPR) will now be prepared, clearing path for construction to begin. The Indrapuri reservoir scheme envisages construction of a storage dam across the Sone, linking sites near Kadwan (Jharkhand side) and Matiawan (Rohtas district, Bihar). It will create a reservoir with a gross storage capacity of about 4,170 million cubic metres at a full reservoir level of around 173 metres. An earthen dam measuring 3.9 km long and up to about 45 metres high forms the core structure, along with a gated spillway, power intake and dam-toe powerhouse. Water resources department (Bihar) secretary Chandra Shekhar Singh, who was present during the signing of agreement in Delhi, said the release of water from the reservoir will be regulated according to irrigation demand at the existing Indrapuri Barrage, located roughly 70 km downstream. "The project includes a hydropower component expected to generate around 300 MW. Benefits also cover municipal and industrial water supply and flood moderation," he added. A senior executive engineer of WRD supervising the project said irrigation networks across eight districts in south and central Bihar such as Rohtas, Bhojpur, Buxar, Kaimur, Aurangabad, Patna, Gaya and Arwal would be strengthened. "After construction of the reservoir, the department would be able to provide sustained irrigation to parched south Bihar tracts-particularly Rohtas, Kaimur, Aurangabad, Gaya and Arwal-where the historic Sone canal system has long struggled to deliver reliable water, especially during Rabi cropping season," he said. As of now, these areas rely on erratic rainfall and water accumulated in ahars-paains, as the water released from the existing barrage hardly flows to canal tail ends during the summer. According to WRD officials, the older low-level canal system had a gross command area of around 6.88 lakh hectares and a cultivable command area (CCA) of about 5.60 lakh hectares, with annual irrigation potential historically cited near 6.95 lakh hectares. "Additional high-level canals expand the overall reach. Once the reservoir is in place, regulated storage is expected to enhance both the reliability and intensity of irrigation across this command, bringing larger extents under assured cover and restoring water supply to stretches affected by siltation, encroachments and inadequate lean-season releases." he added. A retired WRD chief engineer Phulan Prasad said total irrigation network of Sone command area could go up to 11 lakh hectares, though final figures will be firmed up in the fresh DPR. Beyond irrigation, the reservoir will generate hydropower, adding roughly 300 MW to the state's energy pool. Flood control benefits will help moderate peaks on the Sone. Municipal and industrial supplies can be augmented, and related lift schemes-for drinking water to Dehri, Sasaram and parts of Kaimur, for instance-become more viable. For farmers, the key gains will be assured rabi irrigation on lands that remained rain-dependent or under-served, higher cropping intensity, improved yields of wheat, pulses and oilseeds, greater drought resilience and better farm incomes. The Bihar government stands to strengthen overall water security in the Sone basin, reduce the gap between irrigation potential created and utilised, and support agricultural productivity in a critical region. A chief engineer rank officer, anonymously said that the initial cost of the reservoir project was pegged around Rs.1,111 crore, with roughly Rs.533 crore for the reservoir component and Rs.578 crore for power. "The project cost went substantially higher to Rs.12,000 crore in a 2020 pre-project report, reflecting updated land acquisition, construction and other costs. With a fresh DPR now required, the revised estimate is expected to be significantly higher than original figures, subject to current prices, design finalisation and clearances," he said. The Sone canal system ranks among India's oldest major irrigation networks. An anicut was constructed at Dehri in the early 1870s during the British period, irrigating large tracts in the then Shahabad, Gaya and Patna regions. The Indrapuri barrage-1,407 metres long and one of the world's longest-was built about 8 km upstream and commissioned in 1968, with link canals connecting it to the older system. Upstream developments, including storages in Madhya Pradesh and Uttar Pradesh, reduced downstream flows. The 1973 Bansagar Agreement among undivided Bihar, Madhya Pradesh and Uttar Pradesh sought to secure Bihar's 7.75 MAF share. After Jharkhand's creation in 2000, the division of that share remained unresolved, stalling the Indrapuri reservoir. Canal siltation, encroachments and insufficient regulated supply left many tail-end reaches dry, particularly in summer and for rabi crops. The July 2025 understanding at Eastern Zonal Council meeting chaired by Amit Shah, followed by cabinet approvals in both states and Central Water Commission vetting, has now been formalised. WRD officials hope the reservoir will restore reliable flows to the full canal network, giving the long-cherished project the fresh start Bihar's farmers have awaited for generations....