Rainfall totals for parts of Bay Area so far are staggering

Northern California and the San Francisco Bay Area have seen a parade of storms since last December, and the rainfall totals are beginning to add up as the local reservoirs fill up.

The National Weather Service said Monday morning that its gauge at the San Francisco International Airport had recorded 20.30 inches since Oct. 1, surpassing the average for a water year, the 12-month period running from Oct. 1 to Sept. 30. This site, on average, records 19.64 inches in a water year.

Water managers use the water year, which follows the water cycle starting in the rainy season and running through spring and summer when the snowpack melts and its runoff flows into reservoirs and streams. 

The weather service’s gauge in downtown San Francisco is already nearing the annual average, which is 22.89 inches from Oct. 1 to Sept. 30. As of Jan. 16, the site has picked up 21.75 inches since Oct. 1, 2022, which is 205% of normal to date. Last year, at this time, the location had measured 16.84 inches. 

On the peninsula, a site in Redwood City has recorded 21.06 inches since Oct. 1, picking up 252% of the average total rainfall to date. To the north, Santa Rosa has measured 25.08 inches of rain, bringing in 158% of normal to date for the water year.

The Bay Area has received the majority of its rain this season since Dec. 26. Downtown San Francisco, for example, measured 17 inches between Dec. 26 and Jan. 16, making it the fifth-wettest 21-day period in recorded history. 

All of this weather has replenished local reservoirs. In the Santa Clara Valley Water District, four out of 10 reservoirs were full and spilling into waterways, said Matt Keller, a spokesperson for the district. Coyote Reservoir is 111% full, Uvas is 105% full, Almaden is 104% full and Lexington is  103% full.

Keller said it’s not unusual for Uvas, a smaller reservoir, to spill. It’s less common for Lexington, a larger one, to spill. It last spilled in 2017 and 2019. 

“This is good news for our water supply, for sure,” said Keller, adding that all this water came to Santa Clara Valley without any majorly damaging flooding.

In Marin County, all seven reservoirs were full as of Jan. 10. That last time this happened was February 2019.

“It’s super good news, we’re in good shape for shorter-term, which means the next couple years, as our local storage provides around 75% of our water supply,” Adriane Mertens, a spokesperson for Marin Water, said. “Additionally, the Russian River, where the rest of our water comes from, has also recovered. We’re looking good for now. That doesn’t stop our long-term planning effort. We’re going through a districtwide strategic water supply assessment to prepare for future droughts.”

Leave a Reply

Your email address will not be published.