3-Environmental Flow Requirement and its Assessment.

Abstract

Environmental flow refers to the water considered sufficient for protecting the structure and function of an ecosystem and its dependent species. This means enough water is left in our rivers, which is managed to ensure downstream environmental, social and economic benefits. So, environmental flow is compromise between the development and the ecology of the river. Environmental flow assessment is required to be done in order to understand the natural flow regime of the river which is required to exist for the sustainability of the ecosystem. The two broad categories of the environmental flow assessment are the detailed environmental flow assessment method and the desktop environmental flow assessment method. Both the methods are further divided into several categories out of which it is the Desktop Analysis that is used mostly. All the methodologies still needs some modifications as these methodologies are not global and are data intensive. In India previously it was the Tennant Method of environmental flow assessment that was used for the computation of environmental flow requirement but in recent years, the Desktop Reserve Model, Flow Duration Curve Analysis and Hydrological Analysis is also made use of. Sound environmental flow management hedges against potentially serious and irreversible damage to freshwater ecosystems from climate change impacts by maintaining and enhancing ecosystem resiliency. Progress has been made, but much more attention is needed. Several governments have instituted innovative water policies that explicitly recognize environmental flow needs. Environmental flow needs are increasingly being considered in water infrastructure development and are being maintained or restored through releases of water from dams, limitations on groundwater and surface water diversions, and management of land use practices. Even so, the progress made to date falls far short of the global effort needed to sustain healthy freshwater ecosystems and the economies, livelihoods, and human wellbeing that depend upon them,