California hydro-power has dropped enormously because of the drought. The lower water levels put less pressure at the intakes to the turbines, and they generate less power. At some minimal lake height, they wobble so much that they cannot operate. Hoover Dam on the Colorado at Lake Mead has been replacing its turbines to work at lower water levels than before.
California hydro-power has dropped from 23% of state power down to only 7% of state power this year. It has dropped 60% in the last four years. Hoover Dam has dropped 25% in power since 2000. From tree ring studies, this is the fourth worse drought in California in the last 1,000 years.
Fortunately, the Bonneville Power Plant on the Columbia River has remained steady since its origins is in Canada, outside the drought zone.