Before and after: New photos show remarkable recovery at California’s most beleaguered reservoir

By Rachel Ramirez and Will Lanzoni, CNN

California’s drought-stricken reservoirs have seen a remarkable recovery after a barrage of storms lashed the state last month. Officials say it’s a much-needed improvement after hovering at critically low levels for the past several years.

Lake Oroville, California’s most beleaguered and second-largest reservoir, saw a huge boost after the climate change-fueled megadrought sucked away nearly all of its water supply.

Before-and-after photos show incredible improvement at the reservoir, which as of this week stood at 115% of the historical average for the date — a notable jump from just 61% in February 2021 and 77% in 2022.

The before images show a “bathtub ring” of dirt around the edge of the lake, marking how far the water levels had fallen. By late January, the after images showed the bathtub ring was underwater once again.

“However, for every day it doesn’t rain or snow during our wettest months, we are drying out,” Margaret Mohr, deputy director of communications for the California Department of Water Resources, told CNN.

“A lot of uncertainty remains about the next two months and water managers are maintaining reservoirs to hold as much water supply as possible while also managing flood control requirements and preparing for spring runoff.”

California has spent years in desperate need of rain to replenish its reservoirs. The situation was so dire at Lake Oroville in August 2021, a major hydroelectric power plant was forced to shut down for the first time since it opened in 1967 due to low water levels.

The reservoir plunged to just 24% of total capacity in 2021. The lake’s water level sat well below boat ramps and exposed intake pipes, which are used to send water to power the plant.

Shutting down the Edward Hyatt Power Plant served as a wake-up call to how significant the drought had become.

The plant is the fourth-largest hydroelectric energy producer statewide, according to the California Energy Commission, with the ability to power up to 800,000 homes when operating at full capacity. About 13% of the state’s electricity was generated by hydroelectric power plants as of 2018.

Although Oroville’s water levels remained well below average in 2022, storms last winter brought record-breaking precipitation to the Sierra Nevada, which gave the lake’s levels a much-needed boost.

The precipitation was enough to resume power generation at the plant in January 2022, after being offline for roughly five months.

The California Department of Water Resources operates the State Water Project system, which includes Lake Oroville, and provides water to 29 public water agencies serving 27 million Californians and 750,000 acres of farmland.

As the drought continued across much of the state, officials still had to figure out a way to conserve California’s rapidly dwindling water supply. They announced in May 2022 water agencies relying on the state project would only receive 5% of water requests, which went into effect in December 2022 and was supposed to go through this year.

The water agencies were urged to enact mandatory water use restrictions to make their available supplies last.

After this winter’s storms, California state water officials announced at the end of January it will increase allocated water deliveries to 30% of requested water supplies this year.

The State Water Project’s two largest reservoirs — Lake Oroville and San Luis — gained a total of 1.62 million acre-feet of water, which is roughly enough water for 5.6 million households for an entire year. An acre-foot is the amount of water needed to one acre a foot deep — roughly 326,000 gallons.

While the boost in water levels in Lake Oroville presents good news for California residents and farmers who rely on the reservoir, experts have said the state is going to need a lot more precipitation to make up for the yearslong deficit from the historic Western drought.

Groundwater, in particular, has been much slower to recover than reservoirs. These underground aquifers, which much of California’s Central Valley relies on, still have a long way to go before they are completely replenished from the prolonged, unrelenting drought.

Karla Nemeth, director of the Department of Water Resources, warned during the state’s February 1 snowpack survey this month was not looking promising for more rain and snow.

“I will point out that this is a traditional wet month that is actually starting off pretty dry — and given where the forecasts are, that dryness is expected to continue,” she said.

“What is happening with climate is the timing of that peak [precipitation] is also changing,” Nemeth added. “So we really don’t know, here on February 1, whether or not this is the peak of our snowpack — and those are really important data points that help us manage water in California.”

Lake Oroville just one piece of the puzzle in the larger Western water crisis. While the storms did help reservoirs across much of California, the Colorado River Basin — which supplies water to roughly 40 million people in seven Western states and Mexico — has been drying up at an alarming rate.

The Colorado River feeds Lake Mead and Lake Powell, the two largest reservoirs in the country. Record-low water levels in both lakes have triggered mandatory water cuts for some Western states in the last year. Lake Powell hit a new record-low this month, and Lake Mead has been hovering just above its record low set last year.

It’s all an example of how human-caused climate change is transforming water systems around the world, cranking up temperatures and making droughts more severe and frequent.

“Over the next two months, it is important that we still see periodic rain and snowstorms to keep an above average pace for our precipitation totals,” Mohr said.

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