Performance Analysis and its Implementation of Environmental Flow

Abstract

Flows in river stretches with water resource infrastructure like dams, barrages, and weirs, decreases significantly as a result of water withdrawals for power, irrigation and drinking water and thus impact river ecosystems, downstream uses, livelihood and biodiversity etc. To mitigate such impacts, environmental flows are made mandatory to be released from these structures by the regulatory agencies.. Environmental flows or E-Flows are the temporal and spatial changes in water quantity and quality required for freshwater and estuarine systems to accomplish their natural ecological tasks (including material transport) nad may vary during the year. Recently this subject is under focus especially is Himalayan region where hydropower is being developed and are having perennial flows. For analysing and setting environmental flows, many methods combining hydrology, hydraulics, environmental assessment, and ecology have been developed globally. This study presents an performance assessment of environmental flow releases at diversion structures such as barrages, weirs, and dams, focusing on their impact on riverine ecosystems and overall river health. The study examines the status of E-flow implementation at typical 14 water structures in rivers located in Himachal Pradesh and Uttarakhand, considering the variations in flow during different seasons in relation to river discharge and their designated E-flow. The monitoring system in Himachal Pradesh was reviewed, revealing that at some projects release of the prescribed E-flow (15% of monthly average discharge of 3 lean months in Himachal Pradesh and 20% in Uttarakhand) measured using installed intake sensors was followed, whereas at others projects release is not based on river discharge availability including no releases during lean period. Many projects owners considered the leakage losses from the gates at barrages/weirs/dams as E-flow. The Himachal Pradesh Pollution Control Board (HPPCB) serves as the regulatory authority, responsible for overseeing the implementation and compliance with E-flow policies and guidelines within the state and have well developed compliance procedure. However it requires strengthening for effective implementation of E-flows releases.