New Delhi, June 15 -- The Union environment ministry's Expert Appraisal Committee has deferred its decision on a proposed 1,000 MW dam on the Siyom River in Arunachal Pradesh, directing the developer to establish how much water fish and other aquatic species need to survive - rather than determining releases through the standard formula of a fixed percentage of annual river flow. The EAC, which met on May 25, said environmental flows - the quantity, timing and quality of water that must be released downstream from a dam to maintain river ecology - should be calibrated to species survival requirements. The project proponent had proposed releasing 20% of the river's 90% dependable annual discharge across all three seasonal windows: monsoon (June to September), lean season (November to February) and the remaining months. The committee observed that percentage-based norms of this kind may not adequately address the ecological requirements of aquatic species in the Siyom. The project, located across Siang and Shi Yomi districts, was originally allotted to private developers more than 15 years ago. After little progress, the state government terminated the agreements in April 2021 and transferred the project to North Eastern Electric Power Corporation Limited (NEEPCO) in January 2023. An EAC appraisal in 2013 had directed strict compliance with environmental flow requirements and recommendations from the Siang Basin Study. During the appraisal, the committee sought details about fish diversity and measures to ensure movement across the dam. The proponent said at least 20 species are found in the river and its tributaries....