Storm gave ‘big boost’ to Santa Barbara County rainfall totals. Did it lift lake levels?
Last week’s major storm provided a big boost to rainfall totals in Santa Barbara County, but did little to add to the area’s water supplies.
On Jan. 19, the county overall had received just 12% of the normal rainfall to date for the rain year that runs from Sept. 1 through Aug. 31, according to the Santa Barbara County Flood Control District.
But after the storm that dropped more than 12 inches of rain in some locations, that countywide average had more than tripled, to about 40%.
In contrast, Lake Cachuma, one of the county’s major water supplies, rose only about 9 inches and added a little over 1,600 acre-feet of water. It remains about 26 feet below spill level and only 64.4% full.
“Inflow to the reservoir was very minimal,” Matt Young, the county’s Water Agency manager, told Noozhawk.
He added that most of the additional water Lake Cachuma was a result of rain falling directly on the reservoir.
Rainfall totals were significant in most areas last week, especially in the southwest portions of the county.
The county’s wettest spot was Celite, south of Lompoc, which recorded 12.36 inches of rain. Other notable totals included 11.93 inches at Alisal Reservoir in the Santa Ynez Valley, 10.52 inches at Rancho San Julian southwest of Buellton, 10.02 inches in Tecolote Canyon west of Goleta, 9.93 inches on Refugio Pass along the Gaviota Coast, 7.71 inches on San Marcos Pass, and 6.9 inches at Lake Cachuma.
On the South Coast, Goleta received 5.45 inches, Santa Barbara recorded 3.16 inches, Montecito had 2.11 inches, and Carpinteria received 1.59 inches.
North County totals included 6.87 inches in Lompoc, 4.99 inches in Buellton, 4.76 inches in Santa Ynez, 3.87 inches in Orcutt, and 3.3 inches in Santa Maria.
“It’s a good start, but the problem is the watersheds were really dry to begin with,” Young said.
He pointed out that it generally takes about 10 inches of rainfall on the watersheds that feed the Santa Ynez River in order to create significant runoff into Lake Cachuma.
Since the Sept. 1, 2020, beginning of the rain year, Gibraltar Reservoir upstream of Cachuma has received just over 9 inches of rainfall, with about 3 inches of that coming at the end of December, and the remainder falling last week. It was at 13% of capacity on Monday.
Jameson Reservoir, further upstream on the Santa Ynez River, was at 75.1% of capacity.
The lack of runoff, despite the recent dousing, is due in part to the soils in the backcountry remaining relatively dry.
Officials use what is called the “antecedent index,” also know as AI, to measure soil wetness — 6.0 and below is wet, 6.1 to 9.0 is moderate, and 9.1 and above is dry.
As of Monday, the AI reading at Gibraltar Dam was 8.0, near the drier end of the moderate range, and Figueroa Mountain in the San Rafael Range north of Lake Cachuma was at 8.9.
“Even after that rain, the index is still fairly high,” Young said.
In terms of water supply, what’s needed now is more major storms, Young said.
“It’s getting there,” he said, “but it’s not as though the next storm would give us massive amounts of water.”
The exception would be if an upcoming weather system involved an atmospheric river, in which the storm draws in a lot of sub-tropical moisture from the Pacific Ocean, leading to high rain totals, especially in foothill and mountain areas.
Last week’s storm did involve an atmospheric river, but it took direct aim at San Luis Obispo County and regions to the north, and struck only a glancing blow in Santa Barbara County.
With all that said, for the coming week, mostly sunny skies are expected, with no rain in the forecast through Sunday.
