The California Department of Water Resources (DWR) is deploying a range of monitoring, treatment and infrastructure measures to protect the State Water Project (SWP) from the rapidly growing threat posed by invasive golden mussels.

Golden mussels can colonize pipes, pumps and other water infrastructure, creating biofouling that can restrict flows, damage equipment and increase maintenance requirements. DWR’s response includes expanded environmental DNA (eDNA) testing and inspections throughout the SWP to detect infestations early.

At affected facilities, DWR is using low-dose copper treatments as its primary mitigation strategy while increasing manual cleaning, pipeline flushing, power washing and hand-scraping. Field divisions are also replacing equipment when necessary to limit operational disruptions.

DWR is investing in additional protection for critical facilities, including pumping and hydropower plants, fish protection facilities and hatcheries. The agency is installing ultraviolet treatment systems designed to kill golden mussel larvae, known as veligers, before they settle inside cooling, fire protection and service water pipelines.

The agency is also evaluating chemical treatments, antifouling coatings and operational changes to limit biofouling. DWR is pursuing emergency registration of potassium chloride, or potash, as another treatment option. According to the agency, the chemical can control adult golden mussels at treatment concentrations considered safe for fish and wildlife.

Longer term, DWR plans to research golden mussel biology and treatment methods while incorporating invasive species mitigation into future SWP facility design and planning. The agency is coordinating its efforts with the California Department of Fish and Wildlife, California State Parks, federal agencies, water managers and researchers.

DWR also is expanding watercraft inspections and decontamination at infested SWP reservoirs and urging boaters to follow the Clean, Drain, Dry protocol to help prevent the mussels from spreading to additional water bodies.