News Flash

Recreation & Parks

Posted on: August 1, 2022

Potentially Toxic Algae at Local Lakes and Rivers

Blue green algae in lake

Update: August 1, 2022

On July 31, boat rentals and classes on Lake Ralphine at Howarth Park were suspended following observance of potentially toxic blue green algae throughout portions of the lake. These operations will likely remained closed as a precaution for the next several days.

Original Post: July 20, 2022

On July 19 and 20, the State Water Resources Control Board and North Coast Regional Water Quality Control Board issued advisories for residents to be aware of potentially toxic algal mats and blooms found in the water at the Russian River and Spring Lake in Santa Rosa, which is operated by the County of Sonoma. The County is posting “Toxic Algae Alert” signage at recreational areas based on statewide guidance. The algal warnings at Spring Lake apply to the lake only, where swimming and wading are prohibited. The water in the swimming lagoon at Spring Lake Regional Park, which is separate from the lake itself, is treated and is safe to swim in, according to Sonoma County Regional Parks. 

At the City of Santa Rosa's Lake Ralphine at Howarth Park, inspections on July 21 showed no potentially toxic algae visible in the water near the boathouse and boat dock; however, algal blooms and mats are common during summer months when temperatures are warm and can come and go, being moved by wind in-and-out of areas within the lake. Cautionary signage is posted at Lake Ralphine according to statewide guidance. Additionally, when algal blooms are observed, Santa Rosa Recreation & Parks suspends boat rentals and boating classes on the lake as a precaution. Swimming and wading are prohibited at Lake Ralphine.

Follow Precautions

Children and dogs are particularly susceptible to serious health impacts of toxic algae. If algal mats or blooms are observed, children, dogs, and adults are advised to avoid touching or inadvertently ingesting the material. Dogs that have been exposed to the material should be washed immediately. The Water Boards recommend that people practice these healthy water habits while enjoying the outdoors this summer at local lakes, ponds, rivers, or streams:

  • Heed all instructions on posted advisories if present 
  • Avoid algae and scum in the water and on the shore 
  • Keep an eye on children and pets 
  • If you think a harmful algal bloom or toxic algal mats are present, do not let pets and other animals go into or drink the water or eat scum/algal mats on the shore 
  • Don’t drink the water or use it for cooking 
  • Wash yourself, your family and your pets with clean water after water play 
  • If you catch fish, throw away guts and clean fillets with tap water or bottled water before cooking 
  • Avoid eating shellfish if you think a harmful algal bloom is present 

More Information


California Harmful Algal Blooms Portal 
Sonoma County Environmental Health & Safety: Blue-Green Algae (Cyanobacteria)
California Department of Public Health Resource Page

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