Ecological flow assessment using hydrological and hydrodynamic routing model in Bhogdoi river, India

Abstract

Rainfed perennial streams have a highly disturbed ecosystem. Seasonal drying and wetting are stressful for the spawning and breeding activities of aquatic faunas in those stretches. In this work, an integrated hydrological and hydrodynamic modelling study is carried out to estimate the ecological flow requirement in Bhogdoi river, India, a southern tributary of Brahmaputra river. Escalating anthropogenic activities continuously deteriorating the flow scenarios and degrading the aquatic health in the study area. The consequence of hydrological alterations is addressed in terms of the environmental flow regimes derived from FDCA (flow duration curve analysis) and FDC (flow duration curve) shifting method. Flow rates under different environmental management scenarios are evaluated and based on the analysis it is found that under the existing basin condition a minimum flow of 13.42–18 cumec is required for the river ecosystem. The flow depth and the current speed corresponding to the observed maximum flow and the ecological flow rates are computed from a two-dimensional hydrodynamic routing model. The model is calibrated and validated with the measured data. This eco-hydrological approach will be helpful to undertake the conservation and restoration strategies in the study site.