ANNOUNCEMENT: DWR issues Labor Day Weekend algal bloom update for State Water Project lakes and reservoirs

From the Department of Water Resources:


Sacramento – The Department of Water Resources (DWR) today issued a Labor Day weekend update on the algal bloom status of State Water Project (SWP) bodies of water. The update is based on laboratory results of water sampled this week in these lakes.

  • Pyramid Lake: CAUTION”
    Boaters and other recreational users may swim in the main body of the lake and at the designated swim beaches as long as they avoid visible blooms and scum. Blue-green algae can pose health risks, particularly to children and pets. Do not drink this water or use it for cooking, and do not eat shellfish taken from the lake. For fish caught here, throw away the guts and clean fillets with tap or bottled water before cooking.
  • San Luis Reservoir: “DANGER”
    Water sampled at the Basalt boat launch area on August 28 contained the algal toxin microcystin above the “danger” advisory level. Do not swim in San Luis Reservoir, and keep pets away from the water. Boating is permitted, but jet-skiing and waterskiing are not recommended. Do not eat fish or shellfish taken from the reservoir, and do not use this water for drinking or cooking. Boiling or filtering will not make the water safe. No toxins were detected in nearby O’Neill Forebay.
  • Lake Oroville, Thermalito Forebay, Thermalito Afterbay, Castaic Lake and Lagoon, Silverwood Lake, and Lake Perris: “NO ADVISORY”.

Visitors to all lakes are urged to choose safe water activities while recreating. They should avoid ingesting lake water even in the absence of an algal bloom advisory, and pets should be kept away from water covered by an advisory.

Toxic blue-green algae exposure can cause eye irritation, allergic skin rash, mouth ulcers, vomiting, diarrhea, and cold- and flu-like symptoms. Pets can be especially susceptible because they tend to drink while in the water and lick their fur afterwards.

Bloom conditions can change rapidly, and wind and waves may move or concentrate the bloom into different regions of the lakes. Algal blooms can appear as blue-green, white or brown foam, scum, or mats that can float on the water’s surface and accumulate along shorelines and boat ramp areas.

The Statewide Guidance on Cyanobacteria and Harmful Algal Blooms recommends the following for waters with blue-green algae:

  • Take care that pets and livestock do not drink the water, swim through algae, scums, or mats or lick their fur after going in the water.  Rinse pets in clean water to remove algae from fur.
  • Avoid wading, swimming, and jet or water skiing in water containing algae blooms, scums, or mats.
  • Do not drink, cook, or wash dishes with untreated surface water from these 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 affected waters.  Limit or avoid eating fish taken from these waters; if fish are consumed, remove the guts and liver, and rinse filets in clean drinking water.
  • Get medical treatment immediately if you think you, your pet or livestock have been poisoned by blue-green algae toxins. Be sure to alert the medical professional to the possible contact with blue-green algae. Also, make sure to contact the local county public health department.

For more information, please visit:

California Department of Public Health:

State Water Resources Control Board – Interactive Map Showing Lakes’ Status:

CA Office of Environmental Health Hazard Assessment: Information on Microcystin:

US Environmental Protection Agency: CyanoHAB website:

Click here to view all posted announcements.

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