The algal bloom in the middle of San Francisco Bay in August. The San Francisco Board of Supervisors passed a resolution on Feb. 14 instructing the San Francisco Public Utilities Commission to reduce the number of nutrients it releases into the bay, to help prevent future algal blooms.
The Board of Supervisors this week urged San Francisco’s water-management agency to rethink how it supplies and disposes of The City’s water after an unprecedented red tide overtook San Francisco Bay last summer, killing untold numbers of fish and aquatic life.
City leaders passed a resolution Tuesday instructing the San Francisco Public Utilities Commission to reduce the number of nutrients it releases into the bay and scale back its reliance on the Tuolumne River by ramping up wastewater recycling.
“I thought we had seen it all, between orange skies and fires, sea level rise and the pandemic, but we haven’t,” said District 3 Supervisor Aaron Peskin at a hearing in October. “This summer, we saw something (new) in the 58 years I have lived on the shores of San Francisco Bay — I never recall a red tide that consumed much of the entire bay.”
The algal bloom, though unrelated to The City’s drinking-water supply, brought renewed attention to the health of the bay and its tributaries at a moment when California is seesawing between drought and deluge and entering its second century of water wars, this time with climate change flooding, parching and challenging all water systems.
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“San Francisco plays an outsized role, through water management, in the health of San Francisco Bay,” said Jon Rosenfield, science director at San Francisco Baykeeper. “It has a disproportionate impact both because of its withdrawal of water from the Tuolumne River, which is substantial — and on the other end of the pipe, so to speak, they play a disproportionate role in the nutrient problem to the bay.”
The summer bloom of Heterosigma akashiwo took off due to a confluence of environmental factors, including calm winds and sunny skies, but the rampant nitrogen and phosphorus pollution from sewage systems was a major cause, experts found.
“Nutrients were definitely a contributing factor to the blossoming of that algae bloom,” said Eileen White, executive officer at the San Francisco Bay Regional Water Board. But “to think that we can have massive fish kills in San Francisco Bay every summer — that’s not acceptable.”
San Francisco Bay is one of the most nutrient-rich estuaries in the world. Every day, it receives more than 400 million gallons of treated wastewater from 37 different agencies, carrying some 50,000 pounds of nitrogen and 4,000 pounds of phosphorus into bay waters. High nitrogen levels degrade water quality, making it unhealthy to swim and fish, but it can also sap the water of oxygen, killing wildlife.
And while San Francisco discharges just 12% of the total wastewater that enters the bay, it’s responsible for 20% of the nutrient load. “San Francisco is one of the largest contributors of nutrients,” said Peskin. “Therefore (that) gives us an outsized responsibility to be part of the solution.”
But thus far, solutions like water recycling, which could supply part of San Francisco’s future water supply and clean up the nutrients being dumped into bay waters, are lagging. The SFPUC currently recycles less than 1% of its discharges and provides no treated wastewater for direct or indirect potable reuse, the resolution noted. It also does not have a facility to remove nitrogen from its treated wastewater.
That could soon be changing. This spring, The City will debut a new wastewater recycling plant on The City’s west side that will provide up to 4 million gallons of recycled water per day to irrigate major parks and golf courses. The agency is also exploring new projects for purified drinking water, noted Joseph Sweiss, a spokesperson for the SFPUC.
“Recycling water is a win-win for the environment,” said Peter Drekmeier, policy director at the Tuolumne River Trust. “It will reduce nutrient pollution into the bay that contributes to toxic algae blooms while diversifying the SFPUC’s water supply.”
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Still, implementing full-scale recycling for potable water could be time intensive and costly, a recent SFPUC report found. The agency estimated the initial costs for such projects could inch close to a billion dollars at a moment when utility bills are already out of reach for many residents.
Still, White anticipates that the recent tranche of federal and state investments in climate and infrastructure will help kickstart more projects throughout the region. “People are sharpening their pencils,” she said.
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Battle over the Tuolumne River
But solving nutrient pollution in the bay is just one part of the problem. As the state swings between extreme dry and wet periods, scientists predict that hotter and drier conditions could reduce California’s water supply by up to 10% by 2040.
It’s why this week’s resolution directed the SFPUC to wean itself off its dependence on the Tuolumne River, as the Sierra snowpack, though robust this year thanks to this winter’s parade of storms, has been on the retreat.
“The Tuolumne is the worst performing river in the Central Valley,” said Rosenfield, regarding flow and salmon population. “It is worse than the Feather, worse than the American, worse than the Stanislaus, worse than the Merced. It stands out.”
That’s due in large part to San Francisco’s management of the river, noted Rosenfield, who called the SFPUC a “water hog.” In recent years, as much as 92% of the Tuolumne River’s flow has been diverted or held behind reservoirs, depleting ecosystems and causing salmon populations to plummet. In the 1980s, the river was alive with over 40,000 Chinook salmon. By 2020, the population had dwindled to less than 200.
But the SFPUC, charged with supplying reliable drinking water to San Franciscans and customers around the Bay Area, has been fighting the state’s effort to restore the ecology of the Bay-Delta system, known as the Bay Delta Plan, which requires 40% unimpaired flows from rivers including Tuolumne. The agency has been tied up in years-long litigation over how much water it can give up to fish and ecosystems downstream of its reservoirs.
On average, current unimpaired flows in rivers like the Tuolumne range from 21% to 40% but can run as low as 6% in dry years. “If we don’t get higher flows soon, we’re probably gonna lose The Central Valley salmon population,” said Drekmeier.
Though it remains unclear whether this week’s resolution will compel the agency to clean up its act, many are hopeful that this decision is a step forward for the bay and the river we all drink from.
“It elevates the issue,” said Drekmeier, adding that the San Francisco Board of Supervisors ultimately approves the SFPUC’s budget. They “can have a lot of influence in steering the purse strings.”