San Luis Reservoir Algal Bloom at Danger Level Public Urged To Avoid Water Contact


SACRAMENTO (June 30,2017)– The Department of Water Resources (DWR) said today that people should stay out of the water at San Luis Reservoir in Merced County until further notice and avoid eating fish from the reservoir due to the presence blue-green algae (cyanobacteria).

The blue-green algae advisory level at the reservoir today was increased from “warning” to “danger.” The advisory does not apply to O’Neill Forebay.

The recommendation is based on the potential health risks from the algae. Water sampled on June 26 at the Basalt Boat Launch site at San Luis Reservoir contained 25.8 micrograms per liter of microcystins, a level that prompts danger signs to be posted at the reservoir.

Bloom conditions can change rapidly, and wind and waves may move or concentrate the bloom into different regions of the reservoir. Warning signs have been posted at the Basalt Boat Launch, which is at the southeast corner of the reservoir.

The algae bloom can appear as blue-green, white or brown foam, scum or mats that can float on the water’s surface and accumulate along the shoreline and boat ramp area.

Recreational exposure to toxic blue-green algae 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. T

he Statewide Guidance on Cyanobacteria and Harmful Algal Blooms recommends the following for waters impacted by 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 or jet or water skiing in water containing algae blooms or 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 these areas. Limit or avoid eating fish from these areas; if fish are consumed, remove the guts and liver, and rinse filets in clean drinking water.

• Get medical treatment immediately if you think that you, your pet or livestock might 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 - California CyanoHAB Network:

CA Office of Environmental Health Hazard Assessment:

Information on Microcystin

US Environmental Protection Agency: CyanoHAB website US

Environmental Protection Agency: Anatoxin-a report