Golden Mussels: A Looming Crisis for California’s Farms and Water Supply
California farmers have a serious problem that could disrupt the supply chain to grocery stores where we buy our food. A tiny invader called the golden mussel (Limnoperna fortunei), originally from East and Southeast Asia, has invaded the Sacramento-San Joaquin Delta and is spreading fast. First spotted in October 2024, this invasive mussel threatens the water systems that irrigate the fields that grow and sustain California’s $50 billion agricultural industry. If left unchecked, it could clog pumps, pipes, and reservoirs, disrupt water deliveries, putting a dent in farm production and raising prices on the food we buy for our families. Let’s dive into where these mussels are, how they’re spreading, why they’re worse than other invasive species, and what we can do to protect our food supply.
Where Are Golden Mussels Now?
The trouble started in October 2024 when golden mussels were found at Rough and Ready Island and Turner Cut near the Port of Stockton in the Delta. By mid-2025, they had spread to about 30 locations across the central and southern Delta, a critical hub for the State Water Project (SWP) and Federal Central Valley Project (CVP). These systems deliver water to 27 million Californians and irrigate 750,000 acres of farmland. The mussels also showed up in O’Neill Forebay, a key SWP reservoir in Merced County, in October 2024. And in May 2025, inspectors found live mussels on a boat at Folsom Lake’s Beals Point, which had recently been in the Delta. That boat incident is a red flag—mussels are already hitching rides to new waters.
Golden mussels have been detected across the Delta and in California's major water distribution systems.
How Are They Spreading?
Golden mussels are prolific and sneaky. A single mussel can release up to a million microscopic larvae, called veliger, which float in water for up to a month before latching onto hard surfaces like pipes, pumps, or canal walls. The Delta’s warm waters (41–95°F), low calcium levels (1–50 mg/L), and slightly brackish conditions are perfect for them. Its tidal currents act like a highway, carrying larvae far and wide. Since their arrival, they’ve already spread 50–100 miles across the Delta. Based on studies from South America, where golden mussels spread 10–20 miles a year in the Paraná River, they could reach the Delta’s northern and western edges—like Suisun Bay or the Sacramento River—in the next one to two years If we don’t stop them, the entire Delta could be overrun by 2030, threatening the pumps that send water to California farms.
Inspections of recreational watercraft for invasive species are an important part of slowing the spread across California's water infrastructure.
But it’s not just the Delta. These mussels can move through the SWP and CVP’s vast network of canals and reservoirs. O’Neill Forebay is already infested, and larvae could travel to adjacent San Luis Reservoir in one to two years, potentially clogging water deliveries to Central Valley farms. Lake Oroville, the SWP’s largest reservoir, is at risk too. If mussels reach its small-diameter pipes, like those at the Feather River Fish Hatchery, they could disrupt water quality and fish populations by late 2026. And boats are a huge concern. That Folsom Lake boat shows how easily mussels can spread to other reservoirs if boaters don’t clean their gear properly.
What’s at Stake for Farmers and Consumers?
California farms grow over a third of the vegetables and over three-quarters of the fruits and nuts produced in the United States, according to the California Department of Food and Agriculture (CDFA). The SWP, CVP, along with local irrigation and water districts, are lifelines for California agriculture, and golden mussels could choke them. The Banks Pumping Plant (SWP) and Jones Pumping Plant (CVP) in the southern Delta are at risk of clogged intake screens, which could ultimately reduce water flow to farms in the next year. San Luis Reservoir is a critical piece of the state’s water supply infrastructure not only for farms, but for Silicon Valley’s high-tech industry and important wildlife refuges on the Pacific Flyway. San Luis Reservoir is directly connected to O’Neill Forebay and could see infestations by 2026–2027, disrupting water supplies to the Central Valley and Southern California.
Lake Oroville’s potential infestation could also raise water treatment costs and harm fisheries, indirectly affecting farmers and urban water users who rely on consistent water quality and share many of the same water sources. If these systems slow or shut down for repairs, many crops—whether tomatoes, grapes, leafy greens, or even alfalfa for milk production—could suffer, and so could your pocketbook.
Boats could unknowingly spread mussels to upstream reservoirs like Lake Berryessa or Lake Tahoe. Lake Berryessa, already under boat restrictions, could be infested by early 2026 if inspections fail. Lake Tahoe’s low calcium levels make it vulnerable, with potential infestations by 2026 or 2027. Every boat that isn’t cleaned, drained, and dried is a risk to our water systems.
Why Are Golden Mussels Worse Than Other Invaders?
Golden mussels are a bigger threat than other invasive species like Asian clams, mitten crabs, or quagga/zebra mussels in more recent years. Asian clams, around since the 1980s, compete with endangered Delta smelt for food in the Delta, but don’t clog pipes like golden mussels do. Mitten crabs burrow and disrupt ecosystems but have less of an impact on infrastructure. Quagga and zebra mussels, found in places like Lake Mead since 2007, need higher calcium levels (>12 mg/L) and can’t thrive in brackish water like golden mussels, which easily handle low calcium and salty water conditions. This makes golden mussels a threat to more of California’s water bodies, from the Delta to foothill reservoirs. They also filter-feed heavily, causing toxic algae blooms that degrade water quality, harm fish, and complicate irrigation.
Lessons from Around the World
Golden mussels have wreaked havoc elsewhere. In South America, they’ve clogged hydroelectric plants and irrigation systems in the Paraná River basin since the 1990s, costing Brazil $50 million a year in maintenance and agricultural losses. In Asia, Hong Kong and Japan spend tens of millions annually to clean water intakes and treat algae-infested water, with treatment costs up 15–20%. If golden mussels take hold here, California’s SWP, CVP and other water projects could face added repair and maintenance costs in the hundreds of millions of dollars, passing along more costs to farmers in the form of higher water rates.
What’s Being Done, and How Can You Help?
Thankfully, California’s fighting back. The California Department of Fish and Wildlife (CDFW) and Department of Water Resources (DWR) are leading the Golden Mussel Response Framework. They’re running boat inspections at Lake Oroville, Folsom Lake, and other reservoirs, requiring 30-day quarantines or hot-water decontamination for infested boats. They’re also using environmental DNA to detect mussels early and have allocated $1 million in grants to help boating facilities stay mussel-free.
Let’s Protect Our Water, Farms, and Food Supply
Golden mussels are a serious threat to the water systems that keep California agriculture thriving. They could clog pumps and canals, raise costs, and hurt crop yields in just a few years. With high grocery prices still hurting families, we don’t need more pressure on the system that grows the food we all depend on.
Sources: California Department of Fish and Wildlife, California Department of Water Resources, Water Education Foundation, CalMatters, Recordnet.com, International Water Management Institute
