Environmental Flow Assessment for River Valley Projects Rai N.N.1, Jain Akshat2 1Director, Central Water Commission, New Delhi 2Dy Director, Central Water Commission, New Delhi Online Published on 13 May, 2022. Abstract Water is an essential component of life. Water, energy and transport are the basic components for social prosperity and economic growth of any country. In a developing economy like India as the economic growth and social prosperity is advancing, the demand for water resources projects is also increasing. Consequently, rivers and their ecosystems are coming under immense pressure due to storage, diversion and abstraction of water for various consumptive and non-consumptive uses. So far, we have exploited river basins for various uses, mostly without considering the water requirements of the living systems themselves. Therefore, it is critical to balance the requirements of various human uses and ecological needs in a river system from a basin-wide perspective. In this regard river flows of a certain quantity and quality called as environmental flows (E-Flows) are needed required to maintain the river in desired environmental condition or predetermined state where there are competing water uses. The criteria for estimating environmental flows requirements should imitate the spatial and temporal flow patterns of river flow, which affect the structural and functional diversity of rivers, and which in turn influence the species diversity of the river. All components of the hydrological regime have certain ecological significance. High flows of different frequency are important for channel maintenance, bird breeding, wetland flooding and maintenance of riparian vegetation. Moderate flows are critical for cycling of organic matter from river banks and for fish migration, while low flows of different magnitudes are important for algae control, water quality maintenance and the use of the river by local people. Therefore the element of flow variability has to be maintained in a modified E-Flows regime. The present paper describes the importance of environmental flows, methodologies for environmental flow assessment and methodology adopted for the assessment of environmental flow for a reach of river Ganga between Haridwar to Unnao. Top Keywords Flow Regime, Riverine Ecology, Hydraulic Variables, Habitat Simulation. Top |