This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: What does a healthy river look like? For most of us, an obvious answer would involve two aspects: water flowing through a channel and green vegetation along its banks.
However, in reality, a river's health depends on several factors, such as how much water flows through it, how water moves through the landscape, how that flow changes with the seasons, how sediment moves downstream, how often it spills into its floodplain and how these processes change with the seasons. A new study involving researchers from the Indian Institute of Technology Gandhinagar (IITGN) examined such changes in India's Ravi River downstream of the Ranjit Sagar (Thein) reservoir. By combining long-term discharge data with nearly three decades of satellite imagery, they traced modifications in river flow, surface-water extent, vegetation and human activity across the floodplain.
Published in Next Sustainability, the study underscores the need for sustainable management practices. By storing and regulating water, reservoirs can help meet human needs such as irrigation, hydropower generation and controlled water availability. Among the highest earth fill dams in India, the Ranjit Sagar Dam, constructed on the Ravi at the border of the union territory of Jammu and Kashmir and the state of Punjab, serves these purposes.
Although reservoirs have their fair share of benefits, they can alter a river's rhythm. Regulating a river can change the timing and magnitude of its natural high and low flows. Reservoirs can also trap sediment that would otherwise move downstream.
With less sediment and a different flow regime, downstream channels can respond by eroding, narrowing, deepening or otherwise changing their shape. Indra Mani Tripathi, "In dryland regions, where water availability is already limited, communities and ecosystems may depend on seasonal flows. Even relatively small changes in water can have impacts on biodiversity, water availability and ecosystem functioning in such systems." The first author of this study, Tripathi, is a postdoctoral research associate and Ph.D. alumnus in earth sciences from IITGN.
The researchers compared conditions before and after the Ranjit Sagar reservoir began operating on the Ravi. They used daily river discharge data from 1980 to 2019. In simple terms, daily river discharge is the volume of water that flows through a specific point in the river over a 24-hour period.
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