After a rain-soaked January, SLO County reservoirs see big gains in water levels

Nearly a month of almost constant rain has added a dramatic amount of water to reservoirs throughout San Luis Obispo County, leaving some about 75 percent full.

A rain-filled January has left most areas of the county either closing in on or surpassing their average rainfall totals, a trend not seen in the area for almost five years. As of Tuesday, San Luis Obispo has gotten nearly 23 inches since the rain season started July 1 — more than 10 inches above the average season-to-date total.

As a result, all four of the county’s primary reservoirs have increased their storage — the total amount of water they contain — by at at least 49 percent over the course of the month.

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Ray Dienzo, a technical unit supervisor in the Water Resources division of county public works, said consecutive days of rain have been the catalyst for fuller reservoirs.

“That’s something we haven’t seen in a long time,” he said.

More reservoir water means residents don’t need to use as many resources from the State Water Project and can pump less groundwater, Dienzo said.

North County reservoirs

Rain contributed the most water to North County reservoirs. Santa Margarita Lake has added 13,710 acre-feet to its storage over the course of the month — a whopping 604 percent increase, according to county water data. The reservoir started the month 9.5 percent full and is now 67 percent full.

Lake Nacimiento, which is managed by Monterey County, has gained 202,025 acre-feet, or 218 percent more water, since New Year’s Eve, according to Monterey County Water Resources Agency data. The lake ended December nearly 25 percent full and is now at 78 percent of its capacity.

South County and North Coast water sources

Reservoirs in the South County and near the North Coast didn’t see increases as dramatic as those in northern inland areas, but they still gained a respectable amount of water.

Noah Evans, supervisor of Whale Rock Reservoir east of Cayucos, said the amount of water that reservoirs gain depends on area rainfall and the landscape around the lake, which may or may not allow rain to funnel into the larger body of water.

Whale Rock gained 8,316 acre-feet, or 67 percent more water, over the course of the month, according to city of San Luis Obispo data. The reservoir was at 30 percent of capacity Jan. 1 and is now 53 percent full.

Lopez Lake near Arroyo Grande added 5,431 acre-feet to its storage, a 49 percent increase since the beginning of January, according to county data. The lake began the month 22 percent full and is now at 33 percent of capacity.

Dienzo, the public works technical supervisor, said it’s “premature” to say the drought is over because there are many components to the region’s water supply, including the statewide snowpack and local groundwater percolation. Still, Dienzo said he didn’t expect the drenching San Luis Obispo County has gotten this season.

“It was predicted to be a dry year,” he said.

Lindsey Holden: 805-781-7939, @lindseyholden27

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