California drought could reduce hydroelectric generation to half of normal levels

As part of a supplement to our Short-Term Energy Outlook, we analyzed how drought conditions could affect hydroelectric generation in California this summer. California hydroelectric generation would be 48% less this summer in an alternative case that assumes drought conditions compared with a case that assumes relatively normal water conditions. This shortfall would need to be made up from other sources of electric power supply.

During the 2022 water year, which began October 1, 2021, snowpack reached above-normal levels in December, but dry conditions then persisted through March. As of April 1, which typically marks the peak of snowpack, California’s snowpack had an equivalent water content of 6.9 inches, which is about 40% below the median value from 1991 through 2020. Less snowpack means that, as temperatures warm in the spring, less snow will melt and flow into California’s reservoirs.

We used reservoir storage data from the California Department of Water Resources and inflow forecasts from the California-Nevada River Forecasting Center to develop hydroelectric generation forecasts for six major California hydropower plants: Trinity, Shasta, Edward C. Hyatt, Colgate, Folsom, and New Melones. These six plants collectively accounted for 22% of California’s hydroelectric generation in the previous five years (2017–21). We then used the modeled generation from these plants to estimate California’s overall hydroelectric generation under the two alternative cases.

We expect California’s hydro share of the generation mix for June through September 2022 in the drought scenario would be 8% of California’s total electricity generation, compared with 15% under normal water conditions. In drought conditions, we expect California would import more electricity from other markets and use more in-state natural gas-fired generation. As a result of more natural gas use in the drought case, we expect wholesale electricity prices in western U.S. electricity markets would be 5% higher and energy-related carbon dioxide emissions in California would be 6% higher than the case with normal water supply conditions.