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Golden Mussel, California’s Newest Delta Invader, Is Likely Here To Stay – And Spread
WESTERN WATER NOTEBOOK: Aquatic hitchhiker adds to burden of invasive mussels challenging water agencies across the West

Image shows golden mussels clustered on a buoy, found during a survey in November 2024 at O'Neill Forebay at the foot of San Luis Reservoir in Merced County. The mussels were also discovered for the first time in North America last fall in the Sacramento-San Joaquin Delta and O'Neill Forebay. A new aquatic invader, the golden mussel, has penetrated California’s ecologically fragile Sacramento-San Joaquin Delta, the West Coast’s largest tidal estuary and the hub of the state’s vast water export system. While state officials say they’re working to keep this latest invasive species in check, they concede it may be a nearly impossible task: The golden mussel is in the Golden State to stay – and it is likely to spread.

Announcement

Registration Now Open for Popular Bay-Delta Tour in May; Water Summit Set for Oct. 1
Seats Filling Quickly for Water 101 Workshop and Central Valley Tour in April

Register today for the return of our Bay-Delta Tour May 7-9 as we venture into the most critical and controversial water region in California. Get a firsthand look at the state’s vital water hub and hear directly from experts on key issues affecting the Sacramento-San Joaquin Delta and San Francisco Bay.

The 720,000-acre network of islands and channels supports the state’s two large water systems – the State Water Project and the federal Central Valley Project – and together with the San Francisco Bay is an important ecological resource. You’ll learn firsthand how the drought is affecting water quality and supply that serves local farms, cities and habitat. Much of the water also heads south via canals and aqueducts to provide drinking water for more than 27 million Californians and irrigation to about 3 million acres of farmland that helps feed the nation.

Water News You Need to Know

Aquafornia news The Mercury News (San Jose, Calif.)

Thursday Top of the Scroll: California’s largest reservoir has risen 22 feet, as more rain drenches the state

After an unusually dry January where most of Northern California went without rain for 27 days in a row, the storms have come fast and furious, dramatically improving the state’s water-supply outlook. So much rain fell in the first week of February that California’s largest reservoir, Shasta Lake, near Redding, rose 22 feet. Shasta Lake is 34 miles long. The watershed at the state’s second-largest, Lake Oroville, in Butte County, has received 24 inches of rain in the past two weeks — five times the historical average — sending the reservoir level up 23 feet from Feb. 1 to Feb. 7. And now a new atmospheric river storm is forecast to soak the Bay Area and the rest of the state Thursday and Friday.

Other weather and water supply news:

Aquafornia news San Francisco Chronicle

Storm hitting California may bring ‘damaging’ debris flows. These maps shows areas most at risk

Heavy rain is expected to sweep across Southern California on Thursday, raising the risk of flash flooding and mudflows in and around recent wildfire burn areas. Small mudflows were previously observed around the Palisades burn scar from last week’s storm, but Thursday’s storm will present a more pronounced risk. Thursday could be the wettest day in Los Angeles since February 2024, according to National Weather Service forecasts, with 2 to 3 inches of rain expected.

Other debris flow risk news:

Aquafornia news KJZZ (Phoenix, Ariz.)

Arizona senators ask Bureau of Reclamation to resume funding Colorado River projects

Sens. Mark Kelly and Ruben Gallego are asking the Bureau of Reclamation to ensure projects for Colorado River preservation will still get their funding. The Bureau of Reclamation has already signed off on money for projects across Arizona — including an $86 million agreement to build a recycled water plant in Tucson in exchange for the city taking less Colorado River water over the next 10 years. But in a letter to the agency this week, the lawmakers say their constituents are reporting funding for some of that work has been paused amid the Trump administration’s efforts to freeze federal funding.

Other Colorado River news:

Aquafornia news The Press Democrat (Santa Rosa, Calif.)

Historic pact reached on future Eel River water flows into Russian River

Officials from three counties and the Round Valley Indian Tribes have reached a historic agreement that paves the way for continued diversions from the Eel River to bolster flows in the Russian River. The agreement represents a critical development for anyone whose water comes from the Russian River. The complex accord resulted from years of negotiations to preserve supplemental flows in the Russian River, the water lifeline for residents, ranchers and wildlife in Sonoma and Mendocino counties. The agreement also supports the restoration and fish recovery in the Eel River, which was crucial to securing support from environmental interests, tribes and Humboldt County residents.

Related articles:

Online Water Encyclopedia

Wetlands

Sacramento National Wildlife RefugeWetlands are among the world’s most important and hardest-working ecosystems, rivaling rainforests and coral reefs in productivity. 

They produce high oxygen levels, filter water pollutants, sequester carbon, reduce flooding and erosion and recharge groundwater.

Bay-Delta Tour participants viewing the Bay Model

Bay Model

Operated by the U.S. Army Corps of Engineers, the Bay Model is a giant hydraulic replica of San Francisco Bay and the Sacramento-San Joaquin Delta. It is housed in a converted World II-era warehouse in Sausalito near San Francisco.

Hundreds of gallons of water are pumped through the three-dimensional, 1.5-acre model to simulate a tidal ebb and flow lasting 14 minutes.

Aquapedia background Colorado River Basin Map

Salton Sea

As part of the historic Colorado River Delta, the Salton Sea regularly filled and dried for thousands of years due to its elevation of 237 feet below sea level.

The most recent version of the Salton Sea was formed in 1905 when the Colorado River broke through a series of dikes and flooded the seabed for two years, creating California’s largest inland body of water. The Salton Sea, which is saltier than the Pacific Ocean, includes 130 miles of shoreline and is larger than Lake Tahoe

Lake Oroville shows the effects of drought in 2014.

Drought

Drought—an extended period of limited or no precipitation—is a fact of life in California and the West, with water resources following boom-and-bust patterns. During California’s 2012–2016 drought, much of the state experienced severe drought conditions: significantly less precipitation and snowpack, reduced streamflow and higher temperatures. Those same conditions reappeared early in 2021 prompting Gov. Gavin Newsom in May to declare drought emergencies in watersheds across 41 counties in California.