After an already dry year marked by unrelenting fires, the Bay Area might not be getting the rain relief it needs this winter.
“The three-month outlook for January, February and March has most of California above normal for temperature but below normal for precipitation, and that would also include Marin for below-normal chances for precipitation,” said meteorologist Matt Mehle of the National Weather Service.
The agency is forecasting an 85% chance of La Niña conditions to continue this winter, which tend toward wetter weather in the Pacific Northwest and drier conditions farther south. The Bay Area is somewhere in the middle, Mehle said, but the outlook is drier this year.
While the agency’s main weather gauge at the Marin County Civic Center in San Rafael is still out of service because of construction, an unofficial Kentfield gauge recorded 27.7 inches of rain between the start of the water year on Oct. 1, 2019, through Sept. 30, 2020, Mehle said. The prior year was about 58 inches. A 30-year average for that gauge was unavailable for that gauge, Mehle said.
“The moral of the story there is, last year was pretty dry,” Mehle said.
At Lake Lagunitas, the Marin Municipal Water District recorded 35.3 inches of rain during the water year. That is 67.6% of the average rainfall of 52.2 inches.
Amid the driest February on record for the Bay Area, the district recorded a hundredth of an inch of rain. That was the driest since 1953, when no rain was recorded.
The U.S. Drought Monitor at the University of Nebraska-Lincoln shows close to 85% of the state experiencing dry conditions, with 36%, including Marin, showing severe drought conditions. Last year at this time, 95% of the state was showing drought-free conditions.
California has yet to get the rainfall it needs to recover from the 2011-2017 drought, said Marin County fire Chief Jason Weber.
Another dry winter could further worsen future fire conditions following a record-setting year in which 4 million acres have burned already. This is more than double of the previous record of 1.67 million acres in 2018.
“The damage was done with that drought, and when we see that fire season or our dry season is 80 days longer than it was in the 70s, that has long-term and substantial chronic impacts on our fuels,” Weber said.
An example of this, Weber has said, was the unusual coastal fire, largely driven by dry fuels, in the Point Reyes National Seashore starting in August. The so-called Woodward fire burned close to 5,000 acres before being contained in September.
Moisture levels in live plants have reached a “critical threshold” of 60% in October on Mount Tamalpais, Weber said. For comparison, a 30% moisture level is considered a dead plant.
These drier fuels, combined with the protracted drought and high winds, create a “trifecta” of conditions that can lead to massive fires in October, Weber said.
In anticipation of another potentially dry winter, the Marin Municipal Water District has been frontloading purchases of imported water from Sonoma Water rather than drawing on its seven reservoirs.
“It allows us to stretch our local supply of water when we do that,” said Paul Sellier, the district’s operations director. “If all goes well and what we hope is a rainy season we can draw less on that Sonoma Water if it really starts raining.”
The district’s reservoirs were at 66% capacity as of the end of the water year on Sept. 30, which is 96% average capacity for that date. Last year at this time, the reservoirs were at 121% of average capacity.
The district purchased 4,962 acre-feet of water from Sonoma Water between January and Sept. 30. Last year over the same period, the district purchased 4,706 acre-feet. The district has been authorized by its board of directors to take as much as 9,900 acre-feet. Typically the district only purchases 5,300 acre-feet in a year, which Sellier said the district plans to take by January — six months earlier than it normally would import that amount.
However, Sellier said conservation by customers has a sizeable role to play in stretching the district’s water supply. Between 2013 and 2015, Sellier said, customers were able to reduce water use by 20%.
“Customers have shown their willingness to change their habits and work to provide that best solution,” Sellier said.
The county’s second-largest water district, North Marin Water District, reported its main reservoir at Stafford Lake is at 31% capacity as of Oct. 1, which is down from the average 42% capacity on that date. The district receives about 75% of its water supply from Sonoma Water. Sonoma Water’s two main reservoirs, Lake Sonoma and Lake Mendocino, were at 73% and 62% capacity respectively as of Oct. 7.
Earlier this week, there were hopeful forecasts of two rain systems moving into the Bay Area for the weekend, providing the first few inches of rain to the region and some badly needed relief to fire crews. However, those systems are expected to remain over the ocean, Mehle said.
“We don’t typically see our first most notable rainfall until the end of the month or into November,” he said.
Still, more humidity and cooler temperatures are expected to provide some relief, Mehle said. Dry weather is expected to follow into next week including some offshore northeast winds, he said.
