Lake Hopatcong Improving – But Harmful Algae advisory remains in effect

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On July 3rd the NJ Department of Environmental Protection (NJDEP) conducted a flyover of Lake Hopatcong and found improved conditions in the open areas of the lake, compared to the last visual results.

While Lake Hopatcong is showing visual improvements, physical testing performed on July 1st and 2nd still showed that cell counts for cyanobacteria causing the Algae remain above the New Jersey Health Advisory Guidance levels.

Therefore, the NJDEP advises continued closure of public swimming beaches and recommends the public avoid bodily contact with lake water. This means swimming and watersports such jet-skiing, water-skiing, paddle-boarding, canoeing or kayaking should be avoided.

NOTE: There is no suggested limitation on more passive boating that does not involve bodily contact with lake water.

The next planned sampling event will be on Friday, July 5. Additionally, on July 2nd the NJDEP released the following FAQ to help inform the public:


July 2, 2019

Do not have bodily contact with the water. Harmful Algal Blooms can make you sick if the water touches your skin. Do not swim, wade, splash or engage in any other activities that put you in direct bodily contact with the water in Lake Hopatcong.

This also includes kayaking, water-tubing and jet-skiing. Boating (e.g. deck boats, pontoon boats) is still safe, as long aspassengers do not have contact with the water.

Do not drink the water. Drinking water from the lake is prohibited and can make you sick. HABs can increase the likelihood of illness, especially for small children or immunocompromised persons. Some houses may draw water directly from Lake Hopatcong; do not drink this water. Do not let pets have contact with the water. Animals are also susceptible to sickness from drinking or having bodily contact with the water. Children and vulnerable populations are especially susceptible to sickness from a HAB.


Q: What is the problem at Lake Hopatcong?

A: Lake Hopatcong is experiencing a Harmful Algal Bloom, also known as a HAB. The rapid spread of the bloom may be the result of heavy rainfall carrying nutrient-laden runoff into the lake, followed by periods of very warm weather.

Q: Does this mean Lake Hopatcong is closed to the public?

A: No. The lake is open, but bathing beaches are closed to swimming. The DEP strongly advises the public against coming into bodily contact with the water.

Q: How long will this last?

A: It is unclear how long the Harmful Algal Bloom will last. The duration is influenced by the presence of nutrients in the water and weather conditions.

Q: Are there any concerns about use or ingestion of water from Lake Hopatcong?

A: Yes. At no time should water from Lake Hopatcong be used for drinking, bathing or showering, cooking, or formula preparation for infants. Drinking water from the lake is prohibited and can make you sick. HABs can increase the likelihood of illness, especially for small children or immunocompromised persons. Pets should also be kept from drinking water on the lake.

Q: How is the Harmful Algal Bloom impacting recreational activities on Lake Hopatcong? Can I swim in the water?

A: The DEP advises the public and pets to avoid all bodily contact with water from Lake Hopatcong.

Q: What happens if I come into contact with the water in Lake Hopatcong?

A: Exposure can cause a range of health effects including rashes, allergy-like reactions, flu-like symptoms, gastroenteritis, respiratory irritation and eye irritation. Exposure could be more severe for infants, the elderly or those with compromised immune systems. Seek medical treatment if you experience any of these ailments.

Q: What about boating and fishing?

A: Boating is allowed, but direct bodily contact with the water should be avoided. The DEP recommends avoiding other watersport activities such as jet-skiing, kayaking, wind-surfing, paddle-boarding and tubing. Do not consume any fish caught in Lake Hopatcong.

Q: Is there any risk from breathing the air around Lake Hopatcong?

A: Breathing the air near Lake Hopatcong is not expected to result in a health risk. The NJDEP advisory recommending that recreational activities be avoided at Lake Hopatcong is based on primary contact water exposure (e.g., swimming, wading, kayaking, paddle boarding) to cell concentrations that are above the NJ recreational advisory guidelines, as well as the potential for production of harmful algal bloom toxin levels above these guidelines. While very low levels of these toxins may be present in the air near a waterbody that has a harmful algal bloom, inhalation exposure is much lower than exposures from recreational activities such as swimming. The levels of toxins that have been measured in Lake Hopatcong during the harmful algal bloom are far below those that would create a risk from breathing the air near the lake.

Q: What if I have questions?

Visit the DEP Press Release:

Learn about Algal Blooms:

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