Environmental Flows: Concept, Methods, Case Studies and Implementation Challenges in India

ABSTRACT These days, Indian rivers are under tremendous stresses as increasingly larger quantities of water are withdrawn to meet ever‐increasing demands caused by population and industrial growth, flow regulation and fragmentation, land‐use changes, sediment mining and changing climate. One way to keep rivers healthy is through environmental flows (Eflows), whereby time‐ and space‐varying quantities of water are released into the river to maintain its ecosystem. This paper discusses the Eflows concept and estimation methods. Selected case studies from India have been described in which the methods used include hydrological, hydrology + hydraulics and Building Block Method. A detailed analysis of Eflows assessment for the Ganga and Yamuna rivers has been presented keeping in view the practical aspects. I suggest that Eflows assessments should consider physical processes such as river–aquifer interaction, particularly in the case of alluvial rivers. Water quality aspects may also be considered if water quality degradation is due to changes in flow regimes. Keeping in view the large size of India, variability and the number of rivers, there is a need to determine Eflows requirements for different river reaches in the country. The paper has also discussed barriers to Eflows assessment and implementation, technical and policy‐related challenges and follow‐up actions for wider Eflows implementation. For successful Eflows implementation, the general public needs to be associated with environmental preservation.