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Stay Healthy While Recreating in Lakes & Streams

LAKEPORT, CA – With warm weather in the forecast and recreational water sports gearing up, health and water resource officials across the state are reminding the public to be mindful of cyanobacteria (also known as blue-green algae).  These are microscopic organisms that naturally occur in all freshwater and marine aquatic ecosystems.  Usually, cyanotoxin concentrations are low, and not harmful to animals and humans.  Sometimes, when conditions are favorable (high nutrients and warm weather), these organisms can grow rapidly, forming visible colonies or “blooms.”  Cyanobacteria, and even some algae, produce toxins that reach hazardous levels when blooms occur.  These are called cyanotoxins and are classified as Harmful Algal Blooms (HABs).  Blue-green algae is not to be confused with green algae, which is beneficial, non-toxic, and always present in Clear Lake. Water testing is the best way to identify the type of algae that is in the lake at a specific time. During the warm seasons and since 2014, water quality and cyanotoxin testing is conducted about every two weeks at over 20 locations throughout Clear Lake, provided by the Big Valley Band of Pomo Indians and the Elem Indian Colony. To find out if a bloom is occurring and toxins are present, visit the Clear Lake Cyanotoxin Monitoring website at:  This website will have the most current cyanotoxin lab results for the monitoring locations on the shoreline and interior of Clear Lake.  “We are pleased to provide this service to the community; the lake is of utmost importance to our Tribe,” says Big Valley Band of Indians Tribal Chairman Anthony Jack.  “Having current information on toxin levels at recreational and traditional use areas increases our knowledge about the lake and its needs.”

Newly placed since last summer, you will see permanent informational signs throughout the county and cities, at all public parks and public access points that coincide with the water testing locations.  Please see the map showing water testing locations.  No testing locations have reached Caution levels yet this season, and all results showed non-detectable cyanotoxin levels at the last sampling on June 25, 2019. You will see additional signs if cyanotoxins reach Caution, Warning, or Danger levels. The signs will be brightly colored and will be affixed below the permanent informational signs in order to provide the public specific guidance on which activities are safe to continue. The permanent signs are the culmination of a collaborative communication effort between multiple partners: The County of Lake, Big Valley Band of Pomo Indians, Elem Indian Colony, the City of Lakeport, and the City of Clearlake. The signs include a QR code, which can be scanned by a smart phone and will take you the Big Valley Rancheria Clear Lake Cyanotoxin Monitoring website. If you would like to post a sign at your beach or ramp, please contact Water Resources at (707) 263-2344.

If you see, or think you see, a cyanobacteria bloom, please contact Water Resources at (707) 263-2344, Environmental Health at (707) 263-1164, or Public Health at (707) 263-1090.

Algae Map 070919
Algae Text 070919

An example map image from Big Valley Clear Lake Cyanotoxin webpage that shows the most recent testing results and associated sample locations. During summer months, the Tribes sample every two weeks and certified lab results will be shown with this map on their webpage.                                                  

Algae Sign

This picture shows a permanent sign installed at Lakeside County Park.

The Statewide Guidance on Cyanobacteria and Harmful Algal Blooms recommends the following for waters impacted by harmful cyanobacteria:
•    Keep pets and other animals out of the HAB-affected water. Do not allow them to drink the water or eat algal material (scum) on shore.  If they do get in the water, do not let them drink the water, swim through algal material, scums or mats, or lick their fur after going in.  Rinse pets in clean water to remove algal material and potential toxins from fur.
•    Do not drink, cook or wash dishes with untreated surface water from HAB-affected areas under any circumstances; common water purification techniques such as camping filters, tablets and boiling do not remove toxins.
•    People should not eat mussels or other bivalves collected from HAB-affected areas.  Limit or avoid eating fish from these areas; if fish are consumed, remove the guts and liver, and rinse filets in clean drinking water.
•    Get medical treatment immediately if you think that you, your pet, or livestock has gotten sick after going in the water.  Be sure to alert the medical professional to the possible contact with blue-green algae.  Also, make sure to contact Lake County Public Health (707-263-1090) to inform Public Health of potential illness so they can take action as needed.

Remember to always practice healthy water habits:
•    Heed all instructions on posted advisory signs
•    Avoid body contact with water that looks discolored, like spilled paint, or has a green/blue surface scum, mats, or film, or is emitting a foul odor, or if Caution, Warning, or Danger signs are posted.
•    Keep an eye on children and dogs, ensuring that they do not approach areas with water has the above appearance or foul odor, or if Caution, Warning, or Danger signs are posted.  
•    Do not drink untreated lake or river water.  Common water purification techniques such as camping filters, tablets and boiling do not remove cyanotoxins.
•    Do not cook or wash dishes with lake or river water.
•    Wash yourself, your family, and your pets with clean water after lake or river play.
•    Consume fish only after the guts and liver have been removed and rinse fillets.

For current cyanotoxin lab results, please visit the Big Valley Band of Pomo Indians’ cyanotoxin monitoring website: 

For more information, please visit:
County of Lake Cyanobacteria brochure:

County of Lake Cyanobacteria brochure (in Spanish):

California Harmful Algal Blooms Portal:

Physician Reference Sheet:

Domestic Animals and HABs:

County of Lake Cyanobacteria Webpage:


California Cyanobacteria and Harmful Algal Bloom (CCHAB) Network:
California Surface Water Ambient Monitoring Program Freshwater HAB webpage:  
Centers for Disease Control and Prevention (CDC):

U.S. Environmental Protection Agency: CyanoHAB website

Water Faucet
Urgent Health Advisory

Effective immediately, people on private water systems whose tap water comes from their own private intake into the lake, in the Oaks Arm and Lower Arm of Clear Lake should not drink the water.

More info