Castaic Lake algal bloom prompts danger advisory

Press release

News release 

The state Department of Water Resources is urging people to avoid physical contact with water at Castaic Lake until further notice due to the presence of blue-green algae. People should also avoid eating fish or shellfish from the lake, according to the DWR advisory. 

This week’s lab results show an increase in toxin levels. A danger advisory was put in place Tuesday, and remains in effect for the entire Castaic Lake, except Castaic Lagoon, until further notice. It is advised for people and pets to stay out of the water and avoid contact with algal scum in the water or on shore. Boating is allowed, but water-contact recreation and sporting activities are not considered safe due to potential adverse health effects.  

For latest conditions and danger advisory information, go to

Advisories are based on the potential health risks from algae. Exposure to toxic blue-green algae, also known as cyanobacteria, 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 afterward. People are advised to keep pets away from the water. 

Bloom conditions can change rapidly, and wind and waves may move or concentrate the bloom into different regions of the reservoir. The algal bloom can accumulate into mats, and scum, form foam at the surface and along the shoreline, and range in color from blue, green, white, or brown. 

State guidelines on cyanobacteria and harmful algal blooms recommend the following precautions be taken in waters impacted by blue-green algae: 

• Take care that pets and livestock do not drink the water, swim through algal blooms, scum, or mats, or lick their fur after going in the water. Rinse pets in clean water to remove algae from fur. 

• Avoid wading, swimming, or jet or water skiing in water containing algal blooms, scum, 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. 

• Do not eat mussels or other bivalves collected from these areas. No fish should be consumed under a danger advisory. 

• Get medical treatment immediately if you think that you, a family member, friend, pet, or livestock might have been poisoned by blue-green algae toxins. Be sure to alert medical professionals to the possible contact with blue-green algae. Also, make sure to contact the county Public Health Department. 

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