Global Trends in Environmental Flow Assessment: An Overview

Diminution of riverine ecosystem is one of the major challenging issues which is caused due to the alteration of river flow in order to meet the day to day increase in requirements of human being. These alterations in river flow is mainly due to the construction of storage, diversion and control structures which are primarily for generation of electricity, irrigation and flood control. Recently, environmental flow assessment has advanced in the past decade in order to improve the environmental degradation to certain degree. This paper reviews various methods for assessing environmental flow (EF) and provides global trends. We observe that, most of the methods involve different set of data and time requirements. Moreover, the reliability of results and the level of experience required to apply the different methods are different and that no method is superior over the other. The procedure of environmental flow analysis and application is adaptive which involves likewise fluctuation in EF due to increase in the available information and change in priority and infrastructure. This review of case studies of global rivers provides an insight into the environmental flow assessment obtained through hydrological and hydraulic rating method ranged from 30 to 50% of mean annual flow. Other methods for environmental flow assessment are dependent on various ecosystems. Furthermore, the discussion on various methodologies applicable for EF assessment of Indian rivers is also provided in the article. © 2018, The Institution of Engineers (India).