Unraveling the impacts of reservoir regulation and sand mining on the Ravi River, India

Abstract

Dryland Rivers are vital for the earth’s hydrological balance, supporting freshwater supply, food production, and diverse habitats. This study focuses on the downstream impacts of the Ranjit Sagar reservoir on the Ravi River, operational since 2001. We employed modeled discharge data from ERA-5 (European Centre for Medium-Range Weather Forecasts), alongside the remotely-sensed Modified Normalized Difference Water Index (MNDWI) and Normalized Difference Vegetation Index (NDVI). Our findings indicate that dry season discharge (April-May) at the river outlet has decreased significantly by 36% since the reservoir's construction. Water availability decreases fivefold, shrinking from 17.35 km² to just 3.46 km² post-2000 period. Consequently, the diminished river flow has fostered the growth of vegetation within the floodplain. In addition, we observed increased human encroachment in the floodplain, contributed to ponding and other geomorphological alterations over the past decade. Sand mining activities have further intensified channel and floodplain modifications in specific zones, compounding the impacts of reservoir regulation on river health. The findings highlight that the reservoir construction impacts river systems, underscoring the need for sustainable management practices.