Dangerous algae bloom reported northwest of Las Vegas; NPS monitoring coves around Nelson’s Landing

LAS VEGAS ( KLAS ) — State health officials have issued a Harmful Algal Bloom (HAB) warning for Weber Reservoir, the second warning issued since mid-July for a body of water in Nevada.

Weber Reservoir is about 350 miles northwest of Las Vegas. The highest alert — a HAB Danger warning — remains in place at Lahontan Reservoir , about 50 miles north of Weber Reservoir. That warning came on Aug. 19.

Going into Labor Day weekend, officials at Lake Mead National Recreation Area are monitoring coves around Nelson’s Landing at Lake Mohave after positive tests there. That report has not appeared on the Nevada Department of Health and Human Services dashboard, and is being handled by the National Park Service (NPS).

A Lake Mead spokesperson said NPS monitors the beaches at Lake Mead and Lake Mohave routinely, and the Nelson’s Landing report is the first “concerning case” observed this year. Lake Mead has no reports of HABs.

HABs form when blue-green algae multiply quickly and cause discoloration, scum and mats on the water. The blue-green algae are actually single-celled aquatic organisms called cyanobacteria. They are closely related to bacteria and can photosynthesize like algae. Some types of cyanobacteria produce toxins that can affect the nervous system or the liver.

The state reports there have been no illnesses — human or animal — associated with blooms this year.

The advisory for Weber Reservoir issued by the Office of State Epidemiology said, “Hazardous conditions are possible or present. People and pets should use caution when in contact with water and avoid areas of algae accumulation.”

“The greatest danger comes from ingesting the algal toxins,” a Lake Mead spokesperson said on Friday. “For this reason, dogs tend to be heavily affected if they may drink the water. Visitors should be extra cautious with animals or small children playing in or around algal patches.”

In addition to Lake Lahontan (HAB warning), Weber Reservoir (HAB danger) and Little Lake Washoe (HAB danger), seven other lakes/reservoirs are under HAB watches, including Eagle Valley Reservoir in Lincoln County, according to the state’s dashboard. The watch at Eagle Valley went into place on July 8. Those include: Chimney Reservoir in Humboldt County, Nevada Beach Pond in Douglas County, South Fork Reservoir and Wild Horse Reservoir in Elko County, Virginia Lake and Big Washoe Lake in Washoe County.

At Lake Mead and Lake Mohave, officials advise visitors to avoid swimming or wading in water where algae is so thick that visibility is less than 1-2 inches. If visitors spot unusually thick algae, they can call the park’s non-emergency dispatch phone number at (702) 293-8998 or send email to LAKE_Information@nps.gov.

If calling or emailing, it is best to relay the following information: location of algal patch, date, time, and any photos if possible.

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