DWR’s Three-Pronged Strategy to Protect the State Water Project from Golden Mussels

Golden mussels pose a serious and fast-growing threat to California's water infrastructure. As the operator of the State Water Project (SWP), DWR is deploying a comprehensive strategy to mitigate the impact of golden mussel infestation and prevent further colonization. DWR is attacking the problem through several immediate response measures, concentrated investments to strengthen infrastructure, and long-term research and partnerships to improve the state's ability to manage golden mussels.

Immediate Actions: Protecting State Water Project Operations Today

• Vigilant scheduling of inspections, monitoring, and early detection throughout the SWP, including expanded eDNA analysis for golden mussels.

• Implementing low-dose and sustainable copper treatments as the primary mitigation strategy at facilities.

• Increasing maintenance, including manual cleaning, flushing pipelines, power washing, and hand-scraping mussels from vulnerable infrastructure. Some of DWR's field divisions are installing replacement equipment as needed to limit interruptions in operations.

• Preventing further spread through exit watercraft inspections at mussel-infested SWP reservoirs, decontamination programs, and public outreach encouraging boaters to Clean, Drain, Dry.

Midterm Actions: Building Stronger Protection for Critical Infrastructure

• Applying mitigation measures at priority SWP facilities, including pumping plants, hydropower plants, fish protection facilities, and hatcheries.

• Installation of ultraviolet treatment systems to kill larval (veliger) golden mussels before they settle inside critical cooling, fire protection, and service water pipelines.

• Evaluating and deploying additional mitigation tools, including chemical treatments, antifouling coatings, and operational improvements to reduce biofouling.

DWR is pursuing emergency registration of potassium chloride (potash) as an additional treatment option. It is effective at controlling adult golden mussels and is safe for fish and wildlife at treatment concentrations.

Long-Term Strategy: Preparing California for Long-Term Management

• Advancing scientific research to improve treatment methods and better understand golden mussel biology, reproduction, and physiological requirements.

• Developing engineering solutions and incorporating invasive species mitigation into future SWP planning, operations, and facility design to improve long-term resilience.

• Refining monitoring methods and sharing research findings to improve response efforts throughout California and across North America.

Working Together

Golden mussels are a challenge that requires a sustained and coordinated response. DWR works with the California Department of Fish and Wildlife, California State Parks, federal agencies, local water managers, researchers, and the Golden Mussel Task Force under California's Golden Mussel Response Framework. By combining science, engineering, prevention, and collaboration, these partners are working to slow the spread of golden mussels, protect California's water infrastructure, and maintain reliable water deliveries for the millions of Californians and hundreds of thousands of acres of farmland that depend on the SWP.

For more information and additional resources, go to the DWR Invasive Mussel Mitigation webpage. If you observe golden mussels in California, immediately report your sighting to the CDFW Invasive Species Program at [email protected] or (866) 440-9530.