National Park Service (NPS) officials issued a water advisory for Lake Powell just before the July 4 holiday weekend after toxins produced by certain algae were detected.

The alert urged boaters and visitors to use caution and avoid unnecessary exposure to the water, as the toxins present may be harmful to both humans and animals.

Why It Matters

Lake Powell is the second-largest reservoir in the United States, after Lake Mead. The lake is capable of storing more than 24 million acre-feet of water, according to the U.S. Bureau of Reclamation.

According to the Centers for Disease Control and Prevention (CDC), symptoms of illnesses caused by harmful algal blooms can include stomachaches, rashes, headaches, and coughing, while more serious symptoms include liver damage, seizures, and irregular heartbeats.

What To Know

The NPS stated that it detected the presence of cyanotoxins in the mouth of Antelope Canyon in Lake Powell at concentrations that are at the high end of safe exposure levels. These are produced by algal blooms.

Algal blooms can develop due to several contributing factors, the NPS explains. Warm, stagnant water provides ideal conditions for cyanobacteria to thrive, especially when nutrients like nitrogen and phosphorus, often introduced from external sources, are present.

Blue-green algae, the harmful variety, occur naturally in regional waters and are commonly found in Arizona and Utah. These organisms can quickly reproduce, leading to dense blooms and surface scums, particularly in the shallow, warmer parts of the lake, according to the NPS.

To minimize health risks from harmful algal blooms, the NPS advises avoiding contact with affected water. Refrain from swimming in areas where algal blooms are visible and avoid boating, jet-skiing, or water-skiing in scummy water, as these activities can release toxins into the air and increase the chance of inhalation, it said.

Fish caught in these areas should be cleaned using treated water, and all boats and fishing equipment should be thoroughly cleaned, drained, and dried after use. Children should be kept away from algae-covered shorelines, and pets or livestock should not be allowed to swim in or drink contaminated water, the agency advised.

What People Are Saying

The National Park Service said in its water advisory for Lake Powell: “Contact medical care (doctor or veterinarian) if, after exposure to the water, individuals or pets exhibit nausea, vomiting, digestive distress, breathing problems, seizure, or unexplained illness. Water quality staff are sampling and monitoring the situation.”

What Happens Next

The NPS stated that recreation remains open throughout Glen Canyon National Recreation Area, although other parts of Lake Powell, outside the mouth of Antelope Canyon, may also contain these toxins, and visitors should exercise caution.