ABSTRACT
Globally, most rivers have been altered, and these anthropogenic alterations have greatly affected the flow regime, disturbing the riverine processes and their endemic biodiversity. Not only have these imprudent alterations affected the biodiversity, but also, the human race has been affected, facing supra-seasonal extremes like droughts and floods. The macrophytes and ichthyofaunal diversity sustained within these altered rivers have also been affected. The present review covers various aspects of the environmental flows (e-flows) and the altered flow regimes, techniques used for assessing the required e-flows in a river, and also the effect of the human-induced alterations on ecological indicators like macrophytes and the ichthyofaunal diversity. The review suggests that emphasis should be given to a comprehensive modelling of e-flows by integrating the habitat preferences of ichthyofaunal diversity during various stages of their life cycle, including the food web principles of aquatic biota. Besides, e-flow model development should be region specific due to catchment-scale spatial differences. It is recommended that future climatic conditions be included in the model for e-flow assessment given the current trends of increasing intensity of extreme droughts and floods.
