California’s electricity system is inextricably linked to its water system: 19% of the state’s electricity consumption relates to water pumping, conveyance, distribution, treatment, and end-use, and 15% of in-state electricity generation is from hydropower. Projected climate change impacts—including higher temperatures, shrinking snowpack, and more frequent droughts—may exacerbate these interdependencies: e.g. reduced surface water supplies lead to lower hydropower generation, at the same time also increasing electricity demand due to increased groundwater pumping. Further, climate adaptation actions in the water sector can affect the electricity sector because strategies to augment water supplies—such as water recycling, desalination, groundwater recharge, and water use efficiency—add or reduce large electricity demands.

While the climate-sensitivity of some of these individual interactions is acknowledged in the literature, it is not clear from prior assessments how climate impacts on multiple energy-water dependencies may affect the electricity system in aggregate. Together, the impacts from climate change on California’s water system, and especially electricity impacts arising from water sector climate adaptation, may create compounding risks which are currently not accounted for in long-term electricity system planning.

We therefore create a holistic framework for understanding the implications of these cross-sectoral connections for electricity system planning under climate change in California. In the first phase, we develop a reduced-form model of key water and energy resource stocks and flows in order to evaluate the relative importance of each linkage in the context of future climate projections, to reveal overlapping vulnerabilities, and to examine key uncertainties. In the second phase, we link a high-resolution grid planning model with a water resource model focused on California to optimize mid-century grid buildouts given critical linkages identified from the framework. The results will highlight how electricity grid planning and operations can be robust to climate impacts and adaptations from the interdependent water system in California.