The wet weather of the past two years has been a stark contrast to the drought conditions that California has become accustomed to. Floods, landslides, and overflowing streets were a winter staple as storms from atmospheric rivers–so named for their shape and the amount of moisture they carry–dumped buckets of rain on the Golden State.
Now that we’ve moved out of the rainy season into the drier, warmer summer months, we can begin to take stock of the effects of the wet years. These include filled groundwater supplies and lush hills, along with worse allergies and more fuel for wildfires, to say nothing of the considerable toll taken on road infrastructure. Here’s a look at some of the ways that the statewide effects of the rain might show up for Oakland residents.
A historic increase in groundwater levels
Precipitation levels in California are historically unpredictable. The state typically sees large swings between drought years and wet years. But this year was surprisingly average, according to Jeanine Jones, the interstate water resources manager for the California Department of Water Resources.
“We were actually abnormally average,” said Jones. “Snowmelt runoff, depending on which river basin you’re looking at, is really fluctuating pretty close to historical averages, which is unusual for us.”
The last two years of rainier weather may have felt noteworthy for Bay Area residents, but Jones said the more remarkable phenomenon was the colder winter of 2022-23, which led to increased snow.
For the first time since 2019, storage levels for the state’s precious groundwater got a boost. According to the Department of Water Resources, “nearly 85 percent of Californians depend on groundwater for some portion of their water supply, and in dry years when surface water supplies are lacking, communities turn to groundwater to fulfill the needs of households, agriculture, and businesses.”
Due to warmer winter temperatures this year, we are now seeing the effects of last year’s increase in snowpack. A report released by the department this spring found that California was able to increase its groundwater storage by 8.7 million acre-feet. While this is a historic increase, groundwater storage is still in an overall deficit from years of overpumping.
It can be nearly impossible to project California’s precipitation levels and water supply. As weather scientists are now predicting a swing into a La Niña weather pattern for the fall—which are often associated with drier weather conditions for Central and Southern California—it’s far too early to say what that will mean for upcoming precipitation levels, Jones cautions.
“We really can’t predict the future in terms of supply,” said Jones.
Taller grasses
As we head into California’s ever-lengthening wildfire season, we may notice an uptick in fuel sources.
Research has shown a correlation between atmospheric rivers and a more volatile wildfire season. According to a study conducted by the Southwest Climate Adaptation Science Center for the United States Geological Survey, “Atmospheric rivers are projected to increase in frequency and intensity as a result of climate change. … Atmospheric rivers can increase the area burned by fires in the year following an event, particularly in the most arid parts of the interior Southwest.”
California falls under the USGS’s categorization of “Southwest.” The research conducted by the government agency found that the increased moisture brought by atmospheric rivers enriches soils and spurs vegetation growth. However, once the increased vegetation dries out in California’s lengthening warmer months, wildfires are left with more ground fuels to feed on.
“The grasses in particular are much taller than years past,” said Len Nielson, prescribed fire staff chief for the California Department of Forestry and Fire Protection, or CAL FIRE.
Nielson and his team work to address excess vegetation before a wildfire can burn through. They primarily do this through prescribed burning, a technique that allows them to fire-treat an area in a safe and contained manner. This treatment lowers the vulnerability of that area to high-intensity fire later down the line.
While he’s noticed an increase in some fuel sources such as grasses, Nielson said that others have remained fairly consistent.
In the East Bay Regional Park District, denser grasses have made things harder for its fire department, which is responsible for vegetation management.
The park district employs goats, among other maintenance techniques, to help manage grasses. However, Kari Heale, assistant fire chief for the park district, said that the goats have struggled of late to graze quickly enough, thanks to the sheer density of the grasses.
Additionally, the rain has eroded some of the park’s roads, making certain vegetation management areas difficult to access. While the park district is actively working to clear vegetation—including large swaths of eucalyptus trees that died in prior drought years—Heale hopes the public understands the difficulties of addressing the issue.
“Be patient–we are aware of the challenges and we are doing what we can to mitigate the property to make our neighbors as safe as possible,” said Heale.
On a state level, except for a few instances of vegetation-management crews struggling to access locations at high elevation due to increased snow, Nielson sees minimal effects from the atmospheric rivers over the years. His team has managed to treat around 80,000 acres so far this fiscal year. Although they’ve managed to meet many of their goals, both Nielson and Heale agree that it is hard to predict how this fire season will ultimately shake out.
“It’s just too early to tell,” said Nielson.
More sniffles
As the weather has warmed up, many Bay Area residents have noticed an uptick in their allergy symptoms. Research suggests that, as climate change worsens, this may become more and more of an issue for seasonal allergy and asthma sufferers.
Dr. Jyothi Tirumalasetty is a medical researcher and clinician at the Stanford Health Care Allergy, Asthma, and Immunodeficiency Clinic and has been studying the effects of changes in the climate on allergy symptoms.
“We’re seeing earlier, stronger, and longer pollen seasons,” said Tirumalasetty.
Scientists have noticed that, as the climate warms, the allergy season tends to arrive earlier. On top of this, California’s increase in vegetation due to rain has further exacerbated the issue.
Rain usually suppresses pollen, according to Tirumalasetty. But after long periods of suppression coupled with increased growth, the subsequent warmer, drier days can result in higher pollen counts than normal.
As a result, people who tend to be minimally affected by seasonal allergies may feel that their symptoms are worse this year. These can be managed, but Tirumalesetty emphasized the impact that these worsening seasons can have on allergy sufferers.
“It really is difficult for them,” said Tirumalesetty. “Not only do they have the burden of their disease, which can keep them from functioning, doing work [and lead to] missed school days, decreased performance in sports, and also not being able to sleep because you are so congested, you are breathing through your mouth, and your sleep quality is poor. It can really affect quality of life.”
