Scenario-based and scenario-neutral assessment of climate change impacts on operational performance of a multipurpose reservoir

Abstract

Scenario-based and scenario-neutral impacts assessment approaches provide complementary information about how climate change-driven effects on streamflow may change the operational performance of multipurpose dams. Examining a case study of Cougar Dam in Oregon, United States, we simulated current reservoir operations under scenarios of plausible future hydrology. Streamflow projections from the CGCM3.1 general circulation model for the A1B emission scenario were used to generate stochastic reservoir inflows that were then further perturbed to simulate a potentially drier future. These were then used to drive a simple reservoir model. In the scenario-based analysis, we found reservoir operations are vulnerable to climate change. Increases in fall and winter inflow could lead to more frequent flood storage, reducing flexibility to store incoming flood flows. Uncertainty in spring inflow volume complicates projection of future filling performance. The reservoir may fill more or less often, depending on whether springs are wetter or drier. In the summer, drawdown may occur earlier to meet conservation objectives. From the scenario-neutral analysis, we identified thresholds of streamflow magnitude that can predict climate change impacts for a wide range of scenarios. Our results highlight projected operational challenges for Cougar Dam and provide an example of how scenario-based and scenario-neutral approaches may be applied concurrently to assess climate change impacts.

Citation

Danner, Allison G.; Safeeq, Mohammad; Grant, Gordon E.; Wickham, Charlotte; Tullos, Desirée; Santelmann, Mary V. 2017. Scenario-based and scenario-neutral assessment of climate change impacts on operational performance of a multipurpose reservoir. JAWRA Journal of the American Water Resources Association. 53(6): 1467-1482. https://doi.org/10.1111/1752-1688.12589.