Evaluating the Sensitivity of Projected Reservoir Reliability to the Choice of Climate Projection: A Case Study of Bull Run Watershed, Portland, Oregon

Climate change has the potential to alter the quantity and timing of runoff, which may pose significant challenges for reservoir management. One challenge is developing operating policies for an unknown and uncertain future. Here, we develop a suite of ‘optimal’ operating policies for the reservoir system of Portland, Oregon. We assess the sensitivity of projected reservoir reliability to the choice of GCMs and time periods used to develop each of our policies. Results indicate that, while different GCMs and fitting periods produce different optimal operating policies, when those policies are applied across all the other GCM scenarios, the overall projected reliability does not change due to the great variability between simulations. Across the simulations, we note a trend of decreasing reliability in the future which is not sensitive to the choice of GCM or fitting period. This indicates that the projected reliability is dominated by uncertainty in climate projections that cannot be mitigated by tuning operating policies to projected changes.