Improving Socio-Ecological Management of Hydropower Systems Under Climate Change

Dams and storage reservoirs provide a source of water supply, irrigation, renewable energy, and flood protection in river basins around the world. However, human regulation of river systems alters natural hydrologic patterns, which can adversely impact downstream water users and ecological resources. Developing resilient, robust, and adaptive reservoir controls that can balance social, economic, and ecologic outcomes is an essential, yet challenging task. Impact assessments of alternative reservoir operations under a range of possible future scenarios will be essential to inform the design of robust, integrated reservoir control rules.

This study advances the representation of reservoir operations in the Soil \& Water Assessment Tool (SWAT) by integrating nonlinear, multi-reservoir control rules into the model. We consider the Omo River basin of Ethiopia as a case study for the advanced reservoir module, where controversial dam construction provides opportunities for hydropower and irrigation at the expense of indigenous people and aquatic wildlife. We use Evolutionary Multiobjective Direct Policy Search (EMODPS) to optimize reservoir controls that balance the conflicting needs of these stakeholders using both existing SWAT operating rules and our advanced nonlinear control rules. We then perform an impact assessment using the updated reservoir module under alternative climate scenarios to identify policies that continue to balance socio-ecological tradeoffs while mitigating high and low flow extremes under climate change. We find that our advanced operations can better balance conflicting multisectoral needs than existing reservoir operations in SWAT under both historical and climate change conditions, and that our updated policies can mitigate the impact of climate change on high and low flow extremes while continuing to balance socio-ecological tradeoffs.