SOUTH LAKE TAHOE, Calif. – The Lahontan Regional Water Quality Control Board is urging visitors to Silverwood Lake in San Bernardino County to stay out of the water at Cleghorn Beach. Tests in localized areas of the lake confirm the presence of harmful algal blooms. Signage has been posted for the “CAUTION and DANGER” level advisory to warn of the elevated risk.

 A Danger advisory has been issued specifically for Cleghorn Beach and a Caution advisory for the remainder of the lake. Visitors are encouraged to follow the below guidance until further notice. 

Caution – Lakewide

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• You can swim in this water, but stay away from algae and scum.
• Do not let pets and other animals go into or drink the water, or eat scum on the shore.
• Keep children away from algae in the water and on the shore.
• Do not drink the water or use it for cooking.
• For fish caught here, throw away guts and clean fillets with tap water or bottled water before cooking.
• Do not eat shellfish from this water.

Danger – Cleghorn Beach only

• Stay out of the water until further notice, including watercraft.
• Do not let pets and other animals drink or go into the water, or go near the scum.
• Stay away from scum, and cloudy or discolored water.
• Do not eat fish or shellfish from this water.
• Do not use this water for drinking or cooking. Boiling or filtering will not make the water safe.

Silverwood Lake is routinely monitored by the Department of Water Resources to keep the public advised on harmful algal bloom levels. The lake was tested Sept. 26 and lab results show harmful algal bloom toxins present at dangerous levels. The lake will be retested and the advisory may be adjusted once those results are in.

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Note that cyanobacteria, a group of organisms that form harmful algal blooms, can produce potent toxins. Health risks are associated with HABs as they produce dermatoxins that can cause itching skin and rashes, as well as gastrointestinal distress, headaches, agitation and weakness, or abnormal breathing if HAB material is swallowed while swimming. Dogs and children are most susceptible to exposure because of their smaller body size, increased potential to swallow water while swimming, and tendency to stay in the water longer. If you suspect exposure, wash your children and dogs immediately. Due to the size and toxicity of the bloom, it may proliferate and alter its potential to produce toxins. 

The bloom in the lake appears suspended on the water’s surface. Bloom conditions can change rapidly, as the winds and waves move or concentrate the bloom into different regions of the lake. In some areas, the bloom may concentrate and form a film or scum on the water surface. The color of the water may also appear discolored as bright or dark green and brown. 

The Department of Water Resources has posted advisory signs to notify recreational users of the bloom. The Water Board will provide regular updates to inform the community when postings are removed on the California HAB Reports Web Map.

The Water Board recommends that people practice healthy water habits while enjoying the outdoors this summer at your local lake, river or stream: 

• Heed all instructions on posted advisories if present 
• Avoid algae and scum in the water and on the shore 
• Keep an eye on children and pets 
• If you think a harmful algal bloom or toxic algal mats are present, do not let pets and other animals go into or drink the water or eat scum/algal mats on the shore 
• Don’t drink the water or use it for cooking 
• Wash yourself, your family and your pets with clean water after water play 
• If you catch fish, throw away guts and clean fillets with tap water or bottled water    before cooking 
• Avoid eating shellfish if you think a harmful algal bloom is present 

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 cyanobacteria. Also, make sure to contact the local county public health department. 

To report a bloom, do one of the following:

• Fill out the Bloom Report form on the HABs Portal
• Email: CyanoHAB.reports@waterboards.ca.gov
• Call the HABs hotline: 1-844-729-6466 (toll free)
• Contact your County Public Health Office