Reliability, sensitivity, and vulnerability of reservoir operations under climate change

Climate change may critically impair the performance of reservoirs in meeting operational objectives, but reservoirs may also aid in adapting to climate change. To understand how the reliabilities, sensitivities, and vulnerabilities of reservoir operations vary across hydrogeologic settings, a bottom-up approach was applied to investigate the reliability of two water resources systems in the future. To represent the uncertainty associated with future streamflow, global climate model projections were integrated with a formal Bayesian uncertainty analysis and groundwater-surface water hydrologic modeling. Finally, the effectiveness of variable rule curves for mitigating the effects of climate change was evaluated. Increasing air temperature appeared to reduce the reliability of meeting summer environmental flow targets in the future by 42 and 12% for the groundwater basin and surface water basin, respectively, but had negligible impacts on reservoir refilling and flood regulation. Variable rule curves mitigated the impact of climate change on summer flow target reliability without compromising flood risk reduction. Differences in subbasin sensitivity to changing climate were evident across the two hydrogeologic settings, and uncertainty associated with modeling groundwater resources and decision thresholds were identified, with implications for reliability assessments in other basins.