Swelled by heavy runoff from recent large storms, Lake Cachuma is expected to fill and spill by this weekend, according to Santa Barbara County officials.
The lake level continued to rise at the rate of about one foot per hour on Tuesday, and by late morning was at 73.3% of capacity, and about 19 feet below spill level, according to the Santa Barbara County Public Works Department.
“We’ll still be getting inflows to the lake for the next few days,” an obviously happy Matt Young, manager of the county Water Agency, told Noozhawk.
“Just in the last day, it’s come up 34 feet, which is pretty unbelievable.”
Young estimated the lake will reach capacity and begin sending water over Bradbury Dam Friday night or Saturday.
The last time Cachuma spilled was in 2011.
Lake Cachuma poised to overflow
The change in fortunes for Cachuma — and the other upstream reservoirs on the Santa Ynez River, Jameson Lake and Gibraltar Reservoir — is good news for the county’s water supply.
As of early December, Cachuma was at only about 30% of capacity, and water agencies that rely on it were told they would receive no new water allocations from the reservoir this year, Young said.
That will all be revisited and undoubtedly change once Cachuma fills.
It’s also likely local water agencies will receive larger allocations of State Water due to the heavy snowpack in the Sierra Nevada, which will help fill Northern California reservoirs.
More water flowing over the dam at Cachuma also is good news for communities downstream along the Santa Ynez River. The increased flows will help recharge depleted groundwater basins in the Santa Ynez and Lompoc valleys.
However, Young stressed that groundwater basins throughout the county have been drawn down and stressed by pumping during the recent drought, and will need several years of good rainfall to fully recover.
More rain was forecast for the county over the weekend, although nothing of the magnitude of the most recent storm.
Water levels rise at SLO County reservoirs
Recent storms have caused water levels at San Luis Obispo County reservoirs to swell dramatically.
The Salinas Dam at Santa Margarita Lake was overflowing Wednesday with the reservoir at about 109% of its capacity, according to the San Luis Obispo County public works department.
The lake has spilled pretty much as much water as it holds over the past few days, according to David Spiegel, a supervising engineer at the Public Works Department.
As of Wednesday afternoon, the lake was holding about 26,060 acre-feet of water — its capacity is 23,843 acre-feet.
For context, one acre-foot of water is about 325,851 gallons. That means Santa Margarita Lake has about 722.4 million too many gallons within its banks that are overflowing into the Salinas River.
Lopez Lake east of Arroyo Grande also saw huge gains from the recent storms.
Since Dec. 1, the reservoir has nearly doubled in storage. It went from about 10,837 acre-feet to holding 21,594 acre-feet on Wednesday afternoon.
That represents a capacity gain from 21.9% to 43.7%, according to Public Works.
Whale Rock Reservoir near Cayucos went from 28,100 acre-feet on the first day of 2023 to holding 32,292 acre-feet on Wednesday, according to Noah Evans, the reservoir’s manager with the city of San Luis Obispo.
The lake is now at 82.9% capacity, up from 72.1% at the beginning of the month, according to Evans.
Lake Nacimiento also saw massive gains from the recent storms.
The huge reservoir in northern San Luis Obispo County went from 27% capacity holding 103,630 acre-feet of water at the end of December to 73% capacity holding 275,060 acre-feet of water on Wednesday, according to the Monterey County Water Resources Agency.
That’s a gain of 55.9 billion gallons of water.
This story was originally published January 12, 2023 11:32 AM.