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Concerning Cyanotoxin Levels Detected at Nine Clear Lake Sites

Lake County, CA (June 25, 2020) – Many Lake County residents and visitors have recently enjoyed the extraordinary complement of outdoor recreation opportunities that Clear Lake has to offer.  As is the case with all large, biologically rich natural bodies of water, Clear Lake, is dynamic in water quality.  Understanding what signs to look for when recreating can help ensure residents and visitors safely enjoy our County’s defining feature

Water monitoring data is one factor that helps all of us make healthy water-based recreation choices, and lake water monitoring is regularly conducted by the Big Valley Band of Pomo Indians and Elem Indian Colony at approximately 30 Clear Lake sites.  This is a valuable service for all who use our lake.

During the most recent round of sampling, conducted Tuesday, June 23, preliminary testing demonstrated concern for Warning levels of Cyanotoxin at 9 sites (also see orange and yellow indicators on the map, below):
• Elem Indian Colony shoreline (ELEM01, Oaks Arm)
• Austin Park (AP01, Lower Arm)
• Keeling Park (KP01, Upper Arm)
• Sulphur Bank Mercury Mine shoreline (SBMMEL01, Oaks Arm)
• Buckingham (BP, Lower Arm)
• Jago Bay (JB, Lower Arm)
• CL-4 (Oaks arm, center of arm)
• Lily Cove (LC01, Lower Arm)
• Lucerne (LUC01, Upper Arm)

Lab testing results will be available by early next week, and results will be made publicly available.

As previously announced by the Water Resources department, we are noticing extensive patchy algal blooms in various places around the lake:
“Due to the very warm weather and the extended light periods this time of year, the shallow waters of Clear Lake are a perfect environment to encourage growth of aquatic plants, planktonic algae (floating green algae) and cyanobacteria (blue-green algae)… Unlike the young and vibrantly blue reservoirs in CA (such as Pillsbury, Folsom, Barryessa, and Shasta) Clear Lake is never able to draw down it's nutrient & algae-rich water (due to the restrictive Grigsby Riffle rock formation at the Cache Creek outflow), so every year the algae and phosphorus accumulate in the lake, settle into the sediments, and are ready to be used for next summer’s algae blooms!  This is an ongoing cycle.” 

While much of the aquatic plant growth visible in the lake right now is harmless, cyanobacteria, when present in sufficient abundance, can produce cyanotoxins, which pose health hazards to humans, livestock, and pets.

Public Health urges boaters and recreational users to avoid direct contact with or use of waters containing cyanobacteria in Lake County.  The recommendation is based on the potential health risks from cyanobacteria, which is currently blooming at varying levels in the locations noted above. 

Cyanobacteria can pose health risks, particularly to children and pets. We urge people to choose safe activities when visiting natural bodies of water, particularly where blooms are visible.  It is strongly recommended that people and their pets avoid contact with water and avoid swallowing lake water in an algae bloom area.

Lake County Water Resources Department’s Facebook post regarding the current algal bloom, is available here:

Further resources are available at the following webpages:

CDC guidance regarding harmful algal blooms can be found here:

For current cyanotoxin lab results, please visit the Big Valley Band of Pomo Indians cyanotoxin monitoring website and Clear Lake Water Quality Facebook page:

Gary Pace, MD, MPH

Cyano Map 062520

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Mt Konocti Park Meeting

Wednesday, October 20, Lake County Parks & Recreation will host a community meeting to solicit public input for potential improvements and increased recreational opportunities at Mount Konocti County Park.

Meeting info