Staying Safe While Cyanobacteria and Harmful Algal Blooms (HABs) are Present
Below, please find a 2023 Cyanobacteria informational release, originally published April 28. This was prepared by the County of Lake Health Services and Water Resources Departments and Big Valley Band of Pomo Indians, and contains helpful general guidance on what to do when cyanobacteria blooms are present.
To find the most current available information on Clear Lake’s water quality and where cyanotoxin blooms are occurring, visit the Big Valley Band of Pomo Indians’ cyanotoxin monitoring webpage here: https://www.bvrancheria.com/clearlakecyanotoxins
For recent 10-day composite satellite imagery of suspected cyanobacteria blooms in Clear Lake, and other CA water bodies, please visit the San Francisco Estuary Institute Freshwater HAB Satellite Analysis Tool map at this link (please note, satellite imagery is not indicative of toxin levels, it is measuring the amount of phycocyanin pigment that cyanobacteria produces):
Aerial photos recently provided to County officials by Jennifer Strong are included here (please credit Ms. Strong, if these are re-published). Microscopy images, courtesy of Big Valley Band of Pomo Indians, are likewise included (taken from Lake Pillsbury samplings of June 20, 2022).
We sincerely hope the information, images and resources here are helpful, please stay safe!
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Guidance for Recreating Safely Prepared by the County of Lake Health Services and Water Resources Departments and Big Valley Band of Pomo Indians
Staying Safe While Cyanobacteria and Harmful Algal Blooms (HABs) are Present - Officials offer guidance on recreating safely around lakes, reservoirs, and streams
LAKE COUNTY, CA (April 28, 2023, ed. June 26, 2023) - As temperatures begin to rise, regional health and water resource officials are reminding residents and recreationists to be cautious if they are planning activities on local lakes and streams, now and throughout the summer. Cyanobacteria (also known as blue-green algae) are microscopic organisms that naturally occur in all freshwater and marine aquatic ecosystems. Usually, cyanobacteria concentrations are low, and not harmful to humans and animals. But when conditions are favorable (high nutrients and warm weather), these organisms can rapidly grow, forming visible colonies known as “Hazardous Algal blooms” or “HABs.”
The toxic chemicals often produced by HABs are referred to as “cyanotoxins”. Exposure to these toxins causes sickness and other severe health effects in people, pets, and livestock depending on the amount and type of exposure. Sensitive individuals, including young children, the elderly, and people with compromised immune systems are most at risk of adverse health effects attributable to cyanotoxins.
Individuals are most often exposed while swimming or participating in other recreational activities in and on the water. The most common routes of exposure are direct skin contact, accidental ingestion of contaminated water, or accidental inhalation of water droplets in the air (i.e., while water skiing). Symptoms of exposure to cyanotoxins include rashes, hives, diarrhea, vomiting, coughing, or wheezing. More severe symptoms may result from longer or greater amounts of exposure.
People are advised to keep pets and livestock out of water bodies where cyanotoxins may be present. Do not allow pets and livestock to drink from the water and do not allow them to lick their fur after swimming in water containing a possible cyanobacteria bloom. If you or your pet has contact with water you suspect may have cyanotoxins, rinse off with clean, fresh water as soon as possible. If your pet experiences symptoms that may be the result of exposure, contact your veterinarian immediately.
Similar to recent years of extreme drought conditions, self-supplied water systems that draw water directly from lakes and creeks using a private intake, may become unsafe for Lake County residents when greater levels of toxins become present due to limited challenged treatment capability. Public water systems employ multifaceted treatment processes, and are typically able to provide tap water that is safe to drink, despite the presence of cyanobacteria in their source water. For households using self-supplied water systems or a well in close proximity to Clear Lake, and who have not previously participated, testing for contaminants such as cyanotoxins, nitrates, coliform bacteria, and herbicides is available through Big Valley EPA’s Cal-WATCH program detailed here: https://trackingcalifornia.org/calwatch/calwatch-project
If you are concerned you have symptoms resulting from exposure to cyanotoxins, immediately contact your health care provider or call County of Lake Health Services at (707) 263-1090. If you see or think you see, an algal bloom, please contact Water Resources at (707) 263-2344 or Environmental Health at (707) 263-1164. Anyone can report or receive additional information at the California Hazardous Algal Blooms Portal here: https://mywaterquality.ca.gov/habs/.
Cyanobacteria or 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 and toxin levels that are in the lake at a specific time. During warm seasons, water quality testing is conducted every two weeks by Big Valley Rancheria EPA at locations throughout Clear Lake, along local creeks, and at other significant water bodies. Those who plan to recreate in or on Lake County waters should look for informational signs posted throughout the county and are advised to avoid contact with water that:
- looks like spilled, green or blue-green paint;
- has surface scums, mats, or films;
- has a blue or green crust at the shoreline;
- is discolored or has green-colored streaks; or
- has greenish globs suspended in the water below the surface.
The Big Valley Band of Pomo Indians who maintain these water monitoring sites around the lake, has not yet seen caution levels of cyanotoxins this season. Additional signs are posted when cyanotoxins reach Caution, Warning, or Danger levels. These signs are brightly colored and affixed below the permanent informational signs in order to provide the public specific guidance on which activities are safe to continue. Signage is still available, if you would like to post a sign at your beach or ramp, please contact Water Resources at (707) 263-2344.
To find the most current information on Clear Lake’s water quality and if a cyanotoxin bloom is occurring, visit the Big Valley Band of Pomo Indians’ cyanotoxin monitoring webpage here: https://www.bvrancheria.com/clearlakecyanotoxins
For recent 10-day composite satellite imagery of suspected cyanobacteria blooms in Clear Lake, and other CA water bodies, please visit the San Francisco Estuary Institute Freshwater HAB Satellite Analysis Tool map at this link (please note, satellite imagery is not indicative of toxin levels, it is measuring the amount of phycocyanin pigment that cyanobacteria produces):
For additional information about cyanobacteria and harmful algal blooms, please visit the following websites.
Centers for Disease Control and Prevention (CDC):
Environmental Protection Agency (EPA):
County of Lake Health Services Department Cyanobacteria Webpage: