December Storms Ease Crippling Drought that Hindered Hydroelectric Output in 2021

Published: January 14, 2022

By: Concentric Staff Writer

A December storm that brought a deluge of rain and snow to the western U.S. coast rang out a year of intense drought that had hydroelectric project reservoir levels plummeting to alarming lows, illustrating the complex relationship between weather and energy output in all regions.

The close-out of December and the end of 2021 brought much-needed precipitation, particularly to the Sierra Nevada and the Pacific Northwest, which is heavy with hydroelectric generation. But California’s water agency warned that the La Niña season storm is not quite enough to ease concerns about drought in 2022. The California Department of Water Resources’ (“CADWR”) first snow survey of the winter season at Phillips Station west of Lake Tahoe on Dec. 30 showed 78.5 inches of snow depth and a snow water equivalent of 20 inches, which is 202 percent of average for that location on that date.

“We could not have asked for a better December in terms of Sierra snow and rain,” CADWR Director Karla Nemeth said in a Dec. 30 written statement. “But Californians need to be aware that even these big storms may not refill our major reservoirs during the next few months. We need more storms and average temperatures this winter and spring, and we can’t be sure it’s coming. So, it’s important that we continue to do our part to keep conserving – we will need that water this summer.”

The U.S. Drought Monitor said on Dec. 30 that the heavy December precipitation, snow water equivalent numbers (the amount of water if the snowpack melted all at once), and Standardized Precipitation Index figures point to large improvements in the drought for California, parts of Nevada, and Utah. Precipitation between Dec. 21-27 exceeded two inches liquid-equivalent across much of California and western parts of Oregon and Washington state. Temperatures in that period were also below normal across California and the Pacific Northwest, and a more favorable snowpack was building from the Cascades to the Sierra Nevada.

Energy GPS noted on Dec. 30 that the current weather pattern is bringing cooler temperatures across the Midwest, East, and South-Central regions going into 2022. This will increase the marginal cost of energy in those regions, but there are no signs that a similar situation exists to February 2021, when Winter Storm Uri propelled drastic increases in natural gas and electricity prices and led to widespread grid outages, human suffering, and fatalities in the Electric Reliability Council of Texas region.1

However, in the East, the Drought Monitor’s Dec. 30 assessment showed declining soil moisture and an expansion of moderate drought across eastern West Virginia. Abnormal dryness persisted across the northern Mid-Atlantic, where 60-day precipitation deficits range from 2 to 6 inches. Moderate drought also expanded in northern and western parts of Virginia, with short-term precipitation deficits, and there was an expansion of dry conditions across parts of Alabama, Georgia, and the Florida Panhandle.

Experts say that despite the stormy December, it will take an exceptional water year to beat back the devasting drought of 2021, which brought many hydroelectric reservoirs to critically low capacity. For example, low reservoir levels at the 646-MW Edwards Hyatt Power Plant at Lake Oroville, California, caused the hydro plant to shut down in August for the first time since it began operating in 1969. After the storms, the plant resumed operation on Jan. 1, 2022. Over the summer, power production also dropped heavily at Lake Shasta in California’s Central Valley and at the 2000-MW Hoover Dam on the Colorado River.

At the peak of summer, 100 percent of California was experiencing some degree of drought, the snowpack was severely below normal, and melting water from the snowpack often didn’t reach western reservoirs, according to the U.S. Energy Information Administration (“EIA”). EIA expects that data from 2021 will show it was a lower year for hydroelectric output, which was down by 37 percent in the first four months of the year compared with 2020, and 71 percent lower than the same period in 2019. EIA projects that hydroelectric output in California will be down by 19 percent over the entire year from 2020, decreasing from 16.8 million MWh in 2020 to 13.6 million MWh in 2021.

The reduced hydropower output offset an increase in solar and wind generating capacity nationally. This effect put the share of all renewables in the U.S. electricity capacity at about 20 percent in 2021, about the same level as 2020 despite the addition of new renewable projects, EIA said. National renewables output is expected to be about 22 percent of U.S. electricity generation in 2022.

As of Dec. 15, before a strong surge of rainfall caused by the La Niña season, the snow-water equivalent was at 18 percent of the April 1 average and 73 percent of a normal read for the Dec. 15 date. The Central Sierra’s snow-water equivalent was at 87 percent of normal for the Dec. 15 date, and the Southern Sierra was at 97 percent of normal for that date, according to CADWR.

The Drought Monitor reported that dry winter seasons in 2020 and 2021 have created concerns about the Sierra Nevada snowpack, which serves as the “blood supply” for the state’s water system. CADWR announced Dec. 1 that the “initial water allocation” to state water contractors would be at zero percent for the first time. For comparison, the initial allocation in 2020 was 10 percent, and the final allocation in May was 20 percent.

But strong snowfall was predicted for the remainder of the year in the Sierra Nevada, the Cascades in southern British Columbia and the Pacific Northwest, the Great Basin—which includes the Great Salt Lake, Pyramid Lake, and the Humboldt Sink—and the 3000-mile Rocky Mountains that stretch from western Canada to New Mexico.

This will replenish hydroelectric reservoirs that serve Pacific Northwest utilities and electric grids as far away as Arizona, which imports a good portion of Northwest hydropower.

But even as the West shows signs of recovery, drought was still prevalent as 2021 closed out, although precipitation had improved. As of Jan. 4, two to locally six inches of precipitation was reported from the Cascades westward to the West Coast in the Pacific Northwest and parts of California, “further reducing dryness and drought in areas where such conditions have already been removed,” the Drought Monitor said. Some areas in California received more precipitation in the past three months than they had in the prior 12 months, the agency said.

The surge in rain and snow in December shows that weather systems work in cyclical ways, but the impact of drought on power production and water allocations for agriculture and other activities serious. However, for the time being, it seems that the parched soil in the West and throughout the country is beginning to experience some relief.

All views expressed by the contributors are solely the contributors’ current views and do not reflect the views of Concentric Energy Advisors, Inc., its affiliates, subsidiaries, or related companies. The contributors’ views are based upon information the contributors consider reliable at the time of publication. However, neither Concentric Energy Advisors, Inc., nor its affiliates, subsidiaries, and related companies warrant the information’s completeness or accuracy, and it should not be relied upon as such

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