Blue-Green Algae (Cyanobacteria)

Algal Blooms at Riverfront Regional Park

Although we do not monitor the lakes at Riverfront Regional Park near Windsor, visual inspection by a water expert indicates the presence of potentially harmful algal blooms in Lake Wilson. Lake Wilson is a designated non-swimming area as are the other two lakes in Riverfront Regional Parkway. Although swimming is prohibited, many people and their pets visit the shores of the lake and some people fish there. Sonoma County Department of Health Services will be posting warning signs at the three non-swimming lakes to warn the public of the potential risk of cyanobacterial harmful algal blooms.  Although, these lakes are non-swimming, it is important for the public to use caution and follow safe practices, which include not allowing dogs to swim or drink the water and to refrain from eating fish caught in these lakes. Please see "Healthy water habits for recreational river use" on this page.

Please note, currently there are no restrictions along the Russian River.

Algae, including blue-green algae (aka cyanobacteria), is a normal inhabitant of many water environments. Certain conditions, such as high temperatures and elevated nutrient concentrations allow algae to grow more rapidly than usual creating mats or blooms. Most algae is harmless; however, some species of blue-green algae can produce toxins which create health effects for humans and animals. 

DHS works collaboratively with the North Coast Regional Water Quality Control Board (NCRWQCB). Beginning the week after Memorial Day, river condition information, such as data on water temperature and flows as well as visual monitoring (algal mats, stagnation, etc.) is collected and reviewed weekly. When conditions are favorable for the growth of blue-green algae (aka cyanobacteria), laboratory sampling for cyanobacteria toxins will begin. Once initiated, water sample testing will be performed at 10 public beaches along the Russian River. If toxins are detected at a level above the thresholds established by the 2016 California Cyanobacteria Harmful Algal Bloom Network Guidance, DHS will issue public notifications and post signs at the beaches.  Typically, blooms happen later in the summer season. At all times we recommend practicing the healthy habits listed below and keeping your pet away from shallow pools and algae as well as giving them a bath after a day at the river.

Healthy water habits for recreational river use:

  • Do not drink river water. Do not cook or wash dishes with river water.
  • Wash yourself and your family, including any pets, with clean water after river play.
  • Keep dogs away from algae in the river and on the shoreline. Dogs like to eat things and are known to preferentially seek out blue-green algae – they may find something that is otherwise hidden. Be aware of this in deciding how you supervise your dog. Allow your dog to enjoy the open water and keep them away from patches of algae.
  • Bring your life jacket, but leave the alcohol at home. The side effects of alcohol - impaired judgment, reduced balance, poor coordination - can be magnified by the boating environment.
  • If you have concerns regarding your family or pet's health, contact your healthcare provider or veterinarian.

Test Results from Previous Year

State Trigger Levels

CautionAny detected1 μg/L0.8 μg/L
Warning20 μg/L4 μg/L6 μg/L
Danger90 μg/L17 μg/L20 μg/L

Source: State Water Resources Control Board

All levels are in μg/L.

Related Links

Are Harmful Algal Blooms Affecting Our Waters?
Source: State Water Resources Control Board

Algal Blooms
Source: California Department of Public Health.

California Cyanobacteria and Harmful Algal Bloom (CCHAB) Network
Source: California Water Quality Monitoring Council

Harmful Algal Bloom (HAB)-Associated Illness
Source: Centers for Disease Control and Prevention

Contact Information

Public Health Division
County of Sonoma
Business Hours
Monday – Friday
7:30 AM – 4:30 PM
Office Location
625 5th Street
Santa Rosa, CA 95404
38.44178, -122.7158781

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