Officials advise to stay out of San Luis Reservoir water due to algae bloom

The California Department of Water Resources is advising people to stay out of the water at the San Luis Reservoir in Merced County, arguing it is not safe for skin contact.

The advisory is because of recent blue-green algae bloom. The algae is also known as cyanobacteria.


Exposure to the algae can cause eye irritation, allergic skin rash, mouth ulcers, vomiting, diarrhea and cold- and flu-like symptoms.

The department advises that pets are especially susceptible because they tend to drink the water.

Boating is still allowed, but the department is urging against swimming and other water-contact activities.

Basalt Boat Launch and Dinosaur Point Boat Launch has danger signs posted, but O’Neill Forebay does not have any advisories.

The department said bloom conditions can change rapidly. Wind and waves may move the algae into different parts of the reservoir, accumulating into mats and scum, as well as form foam at the surface and along the shoreline.

It’s colors include blue, green, white and brown.

The department published 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 algae 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. Limit or avoid eating fish. If fish are consumed, remove the guts and liver and rinse filets in clean drinking water. 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 local county public health department.
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