Tallying the Western drought's toll on California hydropower

A new report from the Energy Information Administration gets to how much the bad Western drought is sapping hydroelectric generation in California.

By the numbers: "In the first four months of 2021, hydroelectric generation in California was 37% less than in the same four months in 2020 and 71% less than during those months in 2019," notes EIA, the Energy Department's independent stats arm.

As of late June, 33% of the state was under "exceptional" drought conditions, the most severe classification.

Why it matters: It's another snapshot of how climate change can affect energy systems.

• Climate change increases the odds of extreme drought conditions, and hydro generation varies according to snowmelt and rainfall levels.
• The share of hydro in California's power mix bounces around depending on those conditions.
• It provided around 11% of in-state power generation in 2020, down significantly from the prior year, per state regulators.

Threat level: The drought-forced decline in hydro generation reduces one source of carbon-free power generation.

"Reduced hydro output could force California to lean heavily on natural gas-fired generation even as it pushes to reduce its use of carbon-based electricity," Bloomberg reported recently.