Dam Reoperation to Mitigate Changing Climate Extremes in the Omo River Basin, Ethiopia

Climate change is projected to increase the intensity and frequency of extremes in river basins around the world. Water infrastructure such as reservoirs are often used to buffer against these extremes, enabling a more reliable water supply for human uses like irrigation. Yet this can have negative impacts on the system’s ecological flows. In designing water infrastructure for human adaptation to climate change, it is important to consider whether the infrastructure is mitigating or exacerbating climate change impacts on ecological systems. Prior work has found that dams mitigate long-duration extremes but exacerbate short-duration extremes. In this study, we investigate whether reservoir operations can be designed to also yield beneficial climate adaptation outcomes for short-duration high and low flow extremes while still improving average socioeconomic and ecological objectives compared to uncontrolled conditions. We explore this research question in the Omo River Basin in Ethiopia, where controversy surrounding the socioecological impacts of recent and ongoing dam construction makes this a pressing issue to understand. Using multiobjective optimization of reservoir control rules, we are able to find several policies that can in fact mitigate the impact of climate change on annual maxima and annual 7-day minima. While we do see tradeoffs across reservoir operating policies that best preserve the distribution of these two statistics, we also find compromise policies that mitigate both of these extremes compared to uncontrolled conditions. This shows promise for the role dams can play in climate adaptation to short-duration flow extremes if their operations are designed with multiple objectives in mind.