Assessment of e-flows for a river in southern India using hydrological index methods

Abstract

Assessments of environmental flows (e-flows) are emerging trends and new practices, especially in developing country like India. The river Cauvery which is one of the important east flowing river of Southern India having a lot of potential for the development of hydro power projects to satisfy the present demand of power in the Karnataka State. A number of dams have been constructed on this River and its tributaries, which is affecting the downstream ecosystem of river. Therefore, a need arises to regulate the reservoirs for releasing the adequate water in the river throughout the year for maintaining downstream ecosystem as well as a flushing flow once in a year to ensure spawning/regeneration of fish and other species in the river/flood plains. Accordingly, it is essential to estimate e-flows for this river. The e-flows assessment (EFA) method used in the various countries such as France, USA and UK are area specific and the same may not suitable for Indian condition. Hence, in the present study, the e-flows have been assessed using hydrological index methods such as Look-up tables, EMC-FDC approach, Tennant and modified Tennant method, etc. The range of minimum and maximum values of flow computed using these methods were recommended as e-flows with the remarks that the minimum value should be ensured at any circumstances to avoid further degradation of river ecosystem.