NPS Water Recreation Advisory
Anytime that you do recreational activities (swimming, water skiing, making sand castles, etc.) on the beaches or in the waters of Lake Powell you are strongly encouraged to follow basic hygiene practices:
NPS Be On The Watch For Signs of Harmful Algal BloomsWith warm summer water temperatures and plentiful nutrients from monsoonal storms there is a possibility that conditions leading to Harmful Algal Blooms (HABs) may develop. HABs occur when normally occurring cyanobacteria in the water multiply quickly to form visible colonies or blooms. These blooms sometimes produce potent cyanotoxins that pose serious health risks to humans and animals. Stay out of the water and avoid any contact with water or scums if you see pale-green or pea-green scum on or in the water and suspect a waterbody is experiencing a harmful algal bloom. Report potential harmful algal blooms by emailing glca_information@nps.gov with photos and gps coordinates. How to stay safe during HABs
July 2025 HAB questions and answersHarmful Algal Blooms (HABs) can form from blue-green algae that occurs naturally in waters across Arizona and Utah. At low levels, the algae is normally not a threat to human health. However, the algae can sometimes multiply rapidly to form blooms and scums on or below the water surface. Water that is warm, calm, and shallow is perfect for rapid algae growth into blooms. These blooms can concentrate cyanobacteria which produce toxins that affect human health. Nutrients which enter the park and lake from outside sources, such as nitrogen and phosphorus, encourage growth of algae and bacteria. It is difficult to prevent HABs when warm, calm, shallow water conditions occur in nature. Prevention can come in the form of reducing or controlling outside sources of nutrients, such as from stormwater runoff, agricultural runoff, stock yards, or water treatment discharges. At Lake Powell, prevention comes with the assistance of nature. Summer monsoons in the area provide thunderstorms and canyon water flows which help to mix lake water and flush canyons, dispersing harmful algae and bacteria into lower levels, often helping to prevent HABs. No additional restrictions are currently in effect. Glen Canyon National Recreation Area remains fully open for recreation, including for water activities on Lake Powell. Activities involving boats, kayaks, and other approved water devices are still ok. Other activities, such as fishing and swimming, are also ok across Lake Powell and its canyons, with an added caution to look at the water’s surface before you decide to swim, fish or allow your dog in the water. If you see a thin light green film or scum on the water’s surface, or just below the surface, it is best to choose a different water location on the lake to enjoy. This simple practice helps ensure you can enjoy the nature and grandeur of Lake Powell while remaining healthy. For those who wish to hike or ride and explore the land areas of the park, there is plenty of open space to enjoy scenery and wildlife. Our water quality monitoring methods include collecting water samples from algal blooms and using test strips to measure the level of cyanotoxins present. This approach confirmed the toxin microcystin is present in water samples taken from the algal bloom on the water's surface in Antelope Canyon. Drawing a water sample directly from an algal mass floating on the water surface showed a result of >10 ppb (i.e., the measure limit built into the test strips). Using the same water sample, but mixing before testing, the test result was ~7.5 ppb. In regard to swimming, the US EPA recommends a threshold of 8ppb in regard to a determination of concerns to human health. Since our data shows the level of the toxin microsystin is near or above the recommended threshold, Glen Canyon National Recreation Area advises visitors to use caution when recreating at locations in Lake Powell where Harmful Algal Blooms (HABs) occur. Recreational Water Illnesses
Stomach and Intestinal IllnessGastrointestinal illnesses affect a person's stomach and intestines, and can cause diarrhea, nausea, or vomiting. The following gastrointestinal illnesses have been associated with recreational water activities. Cryptosporidium (Crypto)Crypto is one of the most common causes of water recreation diarrhea illness in the United States. The germ is found in people's stool. It's highly resistant to chlorine disinfection and can survive in a pool for as long as ten days. Swallowing contaminated water is how people are often infected. To help stop the spread of Crypto, people with diarrhea shouldn't go swimming. GiardiaGiardia is another common cause of diarrhea found in infected people's stool and beaver are a common carrier. It can take about 45 minutes for this germ to be killed by chlorine disinfection in pools. You shouldn't swim if you have diarrhea and you should always avoid swallowing water while swimming. ShigellaShigella causes severe diarrhea, which is often bloody. It can be spread if an infected person with diarrhea swims or plays in areas such as beaches or inadequately disinfected pools. Having hand washing stations with soap near swimming areas helps keep the water from becoming contaminated. E. coliPeople can get an E. coli infection by swallowing lake water while swimming. Symptoms are similar to Shigella and include severe diarrhea and bloody stool. This infection can be life-threatening and cause permanent damage to the kidneys. Swimming at contaminated beaches are potential sources of infection. NorovirusNoroviruses are very contagious and can spread through an infected person's stool or vomit. The illness often begins suddenly and usually includes nausea, vomiting, diarrhea, and stomach cramps. Chlorine disinfection helps kill this virus in pools, but lakes and beaches can be contaminated. Avoid swallowing water while swimming to help prevent infection. Skin IrritationsSkin rashes, boils, allergic reactions to chemicals, and skin damage from the sun can occur when enjoying water recreation activities. Hot Tub Rash - Pseudomonas dermatitis / FolliculitisHot Tub Rash or dermatitis is an infection that causes an itchy bumpy rash on the skin. The rash usually occurs within days of swimming in poorly maintained hot tubs or spas, but can also be spread by swimming in a contaminated pool or lake. Properly maintaining hot tubs and pools helps eliminate the germ that causes this rash. Swimmer's Itch - Cercarial dermatitisSwimmer's itch is a rash caused by an allergic reaction to parasites that typically infect some birds and mammals. The parasites come from infected snails which live in lakes, ponds, and oceans. People are not suitable hosts for the parasite's life cycle, so after burrowing into a swimmer's skin, the parasite soon dies. Reduce your risk by not swimming in area's known to have a swimmer's itch problem or where snails are commonly found, and showering or towel drying immediately after leaving the water. Swimmer's Ear - Otitis externaSwimmer's ear is an infection of the outer ear canal and can affect anyone, but is most common in children. Symptoms usually start a few days after swimming and include ear pain, itchiness, redness, swelling, and pus draining from the infected ear. It can be treated with antibiotic ear drops. Swimmer's ear is caused when water stays in the ear canal for long periods of time, allowing germs to grow and infect the skin. When swimming, try to keep ears dry. Cyanobacteria – Harmful Algal BloomsCyanobacteria, or blue-green algae, are found in lakes, rivers, ponds, and seawater. Sometimes cyanobacteria is toxic and people can experience skin, eye, or ear irritation with contact. If toxic cyanobacteria is swallowed, it can cause stomach cramps, vomiting, diarrhea, sore throat, fever, headache, muscle and joint pain, or nerve and liver damage. Avoid swimming in or having contact with algal blooms. Don't let pets drink or swim in waters with algal blooms. Chemical SensitivitySome people can experience allergic reactions, such as skin redness and itching, to chemicals used in pools. The reactions commonly occur within an hour or two of being in the water. It's also possible that improper use of chemicals or a chemical release at a pool could expose people to skin or respiratory irritants. Respiratory IllnessSome water recreation illnesses can affect a person's breathing causing cold or flu-like symptoms, shortness of breath, cough, or a serious infection in the windpipe or lungs. LegionellosisLegionnaire disease is a serious infection that creates life threatening pneumonia. Another less serious form of the infection is Pontiac fever, which has the same early symptoms of Legionnaire disease (body pain and weakness, headache, fever, chills, and cough) but isn't associated with pneumonia or death. The germ that causes the disease can be found in streams, ponds or in man-made structures such as fountains or spas. People are typically infected by breathing in contaminated water vapor or steam. Proper maintenance of pools and spas helps eliminate this germ. Lake Powell Water Quality
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Last updated: May 20, 2026