ENVIRONMENTAL FLOWS ASSESSMENT FOR THE RIVER VALLEY PROJECTS

Abstract

Environmental flow (EF) is the amount of water required for healthy sustainability of the river. River systems are often endangered due to construction of water retaining structures such as hydro power generating structures, bridges, etc. Environment flow - assessment is thus aimed at analyzing the minimum flow of water required for the sustainability of ecosystem. The aspect of water scarcity has also been widely discussed in terms of drought, which is known as a temporary random and complex phenomenon mainly occurring due to scarcity of precipitation leading to decrease of water and further leading to economic and environmental loss. Among the various indices available for assessment of drought, the Standard Precipitation Index (SPI) has gained much popularity in the recent past. In the present study, Environmental Flow (EF) is estimated using Termant method (or Montana method) and then this assessment is linked with Standardized Precipitation Index (SPI) frequently used for drought analysis. For validation, this concept is applied to the data of five river basins: Nygamjang Chhu, Eastern Ramganga, Saryu River, Mahanadi, and Tel River. The EF-SPI relations proposed for all basins generally described a consistent pattern, indicating the existence of a relationship between EF and - SPI, which does not appear to have been explored in literature. Such a relationship can be advantageously used for deriving EF for a watershedlgauging site based on SPI, which can be conveniently derived from much more easily available rainfall data and is quite useful for ungauged watersheds.