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Impact of anthropogenic modifications on flow regime: A case study of Upper Cauvery river basin in India


Anjana Ekka is a PhD researcher at the Delft University of Technology, The Netherlands. With a background of a master’s in Agricultural Economics, she has experience working in ecosystem service valuation and socio-economic issues in inland aquatic ecosystems. At present working, she is working on a hydrological-economic modelling approach for river basin management.


Rivers are being exploited for drinking water supply, power generation, flood control, and irrigation in pursuit of economic growth, which substantially impacts river hydrology and surrounding ecosystems. Reservoir construction is one of the major contributors to such changes. Around the world, free-flowing rivers are impaired due to reservoirs, impacting the basin downstream. The interactions between biophysical, social, and economic factors determine the socio-hydrological dynamics and sustainability of the river ecosystems. Cauvery river basin in India is one such example of a basin that has historically been heavily dammed. This study aims to understand the hydrological alterations resulting from the interventions in the upper regions of the basin. Based on size and storage capacities, four large reservoirs are selected. A hydrological model, FLEX-Topo, is used to model flows contributed by upstream and downstream areas of the reservoirs. A reservoir operation model is developed for each reservoir. Each reservoir is calibrated first, then keeping the parameters of the reservoir model fixed, the hydrological model integrated with the reservoir is calibrated using its downstream gauging station. Non-dominated Sorting Genetic Algorithm II is used to calibrate the model parameters. The modelled flow regimes with and without reservoirs are then compared using the indicators of hydrological alterations to understand the degree of flow alterations by the reservoirs. The results indicate that flow regimes have been modified from their natural state following reservoir impoundment and water abstraction. Significant impact is observed in median monthly flow, 1-day minimum flow and low pulses. Such information could provide a reference to water managers to replicate natural-flow regime and help sustaining natural biota and thus contribute towards for the sustainable management of river basin resources in India.

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