Are California Reservoirs Filling Up?

After weeks of torrential rain across California, the state's major reservoirs have seen huge gains in water level.

This has also paralleled the widespread lifting of drought conditions across California: U.S. drought monitor data has shown that between January 3 and January 10, the percentage of the state experiencing "extreme drought"—the Drought Monitor's second most-severe level—dropped from 27.10 to 0.32 percent.

The rain has come as a massive relief to California's water-storage systems after an incredibly dry summer in 2022.

"[2022] has seen the highest percentage of the country, over 80 percent of the continental U.S., be classified as being in a drought since the U.S. Drought Monitor was established a little over 20 years ago," Antonia Hadjimichael, an assistant professor in geosciences at Penn State University, previously told Newsweek.

Some of the largest increases in water level were seen at Lake Shasta, the state's largest single reservoir, situated in northern California.

The lake's water level on December 25, 2022 was 921.11 feet above sea level, while as of January 15, 2023, the water levels are at 973.76 feet. On January 9, the lake was still only at 942 feet above sea level.

The table below shows the changes in the water level of the state's 15 most voluminous lakes since January 9, with water level measured in feet above average sea level.

Source: Lakes Online *Lake Berryessa data from Solano County Water Agency.

However, many of the reservoirs across the Golden State are still at lower water levels than average, even for this time of year.

"Right now, we're at about 80 percent of what we normally would be on today's date," Donald Bader, the Northern California Area Office manager for the Bureau of Reclamation, previously told Newsweek. "We were in the 60s before, on historic average, so we're trending in the right direction, but what concerns us all the time is that the weather can change on a dime."

While reservoirs are being filled up by the deluge of rain, that doesn't necessarily mean that the state will climb out of drought, due to the depleted stores of water in the groundwater.

"Long periods of low rainfall not only dry up the moisture supply for plants (risking fires and large-scale tree mortality events, etc.), they also limit the amount of groundwater that is stored within the landscape," Daniella Rempe, a hydrologist and geomorphologist at the Jackson School of Geosciences, University of Texas in Austin, told Newsweek.

"This groundwater is absolutely crucial to supplying streams in California's long dry summers every year, not just during drought. But what happens during drought is that the rains that would refill this groundwater end up just refilling the dry root-zone and either delaying or preventing recharging of the groundwater system that supplies streams and reservoirs."

Additionally, the effects of climate change may make it harder for California to recover from drought, due to increasingly dry weather.

"Climate change will only exacerbate the feast-famine water cycle in California," Jacob Petersen-Perlman, a water-resources geography expert and assistant professor at East Carolina University in Greenville, North Carolina, told Newsweek.

"However, the drought and flooding disasters often open up opportunities for stronger regulations and stricter management practices that can protect Californians from the worst of these effects."

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