May showers made Sonoma County unusually wet, but didn’t set record

With thunderstorms threatening Thursday, Sonoma County got ready to close out an unusually wet May that helped keep reservoirs full and pastures green, while the Russian River flowed cold and fast, hazardous for swimming and fit only for experienced boaters.

Santa Rosa received 3.42 inches of rain since May 1, well below a record but still far above average for the last full month of spring - a hair under 1 inch.

It was the eighth-wettest May on record since 1903 but no match for the record 5.55 inches that fell on Santa Rosa in 2005 nor the 5.4 inches in 1990.

A low-pressure trough along the West Coast kept a “winter weather pattern” in place for most of May, said Roger Gass, a National Weather Service forecaster.

Nearly all of Santa Rosa’s rain fell in a five-day stretch from May 15 to 19, and it dramatically pumped up the Russian River, prompting Sonoma Water to reverse course on the installation of its seasonal rubber dam on the river near Forestville.

The dam, a critical component of the county water agency’s supply to ?600,000 Sonoma and Marin residents, should now be full in three to five days and will remain inflated into fall, Sonoma Water spokesman Barry Dugan said.

In the first two weeks of May, the river’s flow steadily dropped by half, down to about 550 cubic feet per second (cfs) at Hacienda Bridge. Then in about five days, from May 15 to 20, the river swelled to more than 4,000 cfs and had since tapered off to 1,000 cfs on Thursday

That was low enough for Larry Laba, owner of Russian River Adventures in Healdsburg, to send about a dozen people down the river paddling his inflatable canoes.

“I have a very low tolerance for risk,” Laba said, noting that he was limiting rentals to experienced boaters.

He took a 60 percent hit over Memorial Day weekend with “significant cancellations” that he did not dispute.

Don McEnhill, executive director of the Russian Riverkeeper, said the river at Thursday’s level “exerts a lot more push on a boat,” noting that he canceled a kayak trip for high school students last Saturday.

A flow of about 300 cfs is preferable for beginners, he said, and the typical summer flow is half of that.

In Guerneville, a tourist and recreation hub on the lower Russian River, the holiday was “a horrible weekend weatherwise,” with cool, cloudy conditions and some rain Sunday, said Sue Lange, a Russian River Chamber of Commerce volunteer.

Word that Johnson’s Beach was closed prompted numerous lodging cancellations, she said, and the river is still flowing fast and muddy.

Johnson’s Beach will open this weekend and stay open weekends through June 15, when it switches to daily openings through Sept. 2, said beach operator Chris Abbott.

The summer dam that creates a large swimming area won’t go up until mid-June.

Heavy rains prior to the holiday were a boon, Lange said, as they helped wash away mud and debris from the February floods.

The public beach in Monte Rio, which doesn’t rely on a summer dam, should be open this weekend.

Sonoma County Regional Parks kept its river beaches open in May, but is continuing to advise visitors to stay out of the cold, fast-moving water.

Park crews have been unable to make their usual preseason dives to check for new hazards on the river bottom, said David Robinson, parks manager.

Santa Rosa’s Spring Lake is a safe place to boat and the swimming lagoon is “ready to go,” he said, with filtered and chlorinated water.

The summer dam at Healdsburg Veterans Memorial Beach won’t go up until July 1, he said

May’s rain was a bonus for some ranchers, spurring growth of spring grass for livestock, especially near the coast, said Joe Pozzi, a Valley Ford sheep and cattle rancher.

But it was too late for inland pastures that had started to dry out and no use to ranchers who were preparing to cut tall grass.

“There’s always some give and take in ranching,” he said.

The rain helped keep Lake Sonoma and Lake Mendocino, the region’s two major reservoirs, at or close to water storage capacity.

“We are in great shape water-wise,” said Brad Sherwood, a Sonoma Water spokesman.

Meanwhile, the wet season continued Thursday in Lake County, with thunderstorms dropping heavy rain near Clear Lake and a flash-flood warning issued by the National Weather Service for the southeast portion of the county through 6:45 p.m.

You can reach Staff Writer Guy Kovner at 707-521-5457 or guy.kovner@pressdemocrat.com. On Twitter?@guykovner.