A current National Park Service harmful algae alert says a bloom was confirmed in recent water samples from Nelson’s Landing and Cottonwood Cove on Lake Mohave. The park recommends limiting body contact with the water when algae is present.
The alert changes the plan most for swimming, wading, paddling close to visible scum, and trips with children or pets. Travelers who need to move recreation away from affected water can use Deep Arrival’s Bullhead City activity guide to build a dry backup near the southern lake area.
- Named areas: The active alert identifies Nelson’s Landing and Cottonwood Cove on Lake Mohave.
- Finding: Harmful algae was confirmed in recent water samples, according to the National Park Service.
- Water decision: Limit body contact wherever algae is present and avoid visible mats, scum or discolored water.
- Higher risk: Children can accidentally swallow water, while pets can become seriously ill or die after exposure.
- Status check: Call the park at 702 293 8990 and review current alerts before restoring water activities.
Two Lake Mohave Recreation Areas Are Named
Nelson’s Landing is on the Nevada side of Lake Mohave south of Boulder City. Cottonwood Cove is farther south, also on the Nevada side, and includes a marina and recreation facilities. The notice is location specific. It does not say every mile of Lake Mohave or Lake Mead has the same visible conditions.
The park alert also does not publish a sample date or a fixed expiration date. It was active when checked Sept. 4 and describes the samples only as recent. Travelers should not invent a countdown from an unknown collection date. The current park alert, signs at the water and visible conditions are the useful status checks.
Algae can move with wind, collect in coves, die off or disappear. The National Park Service says its monitoring is intermittent and asks visitors to report suspected blooms. That means a clear looking shoreline in one place does not cancel the named alert, while a bloom seen elsewhere should still prompt avoidance and a report.
Visible Algae Is the Immediate Stop Signal
The park advises avoiding water with algae visible on the surface. Harmful blooms can resemble bright green scum, paint, foam, grass clippings or floating mats. Color alone does not confirm toxicity, but visitors cannot determine safety by sight. The practical rule is to stay out when suspicious algae or discolored water appears.
Nevada’s harmful algal bloom guidance gives the same cautious direction. The state says to avoid swimming in suspect water and not to boat, water ski or use a jet ski on scummy water because spray can put toxins into the air.
A boat launch or marina remaining open is not proof that every water activity is appropriate. The NPS alert recommends limiting body contact when algae is present rather than announcing a full closure. Boaters can confirm local operations separately, but should keep people, pets and equipment away from visible accumulations and reduce spray near a bloom.
Do not drive to another cove and assume it is safe without checking. Wind can move surface material, and conditions can differ from one shoreline to another. Inspect the exact access point before unloading a paddleboard, kayak or swimming gear.
Children and Pets Need the Most Conservative Plan
The National Park Service says harmful algae can produce toxins that cause illness. Possible symptoms after exposure include nausea, vomiting, digestive problems, breathing problems, seizures or unexplained illness. Children face added risk because they may swallow water while playing. Anyone who becomes ill after exposure should seek medical attention.
Dogs and other animals can become seriously ill or die after ingesting water with harmful algae toxins. Keep pets leashed and completely away from suspicious water and shoreline scum. If an animal enters affected water, Nevada guidance says to rinse it immediately with clean fresh water while wearing gloves and contact a veterinarian if symptoms appear.
Do not let a pet drink from Lake Mohave simply because the water looks clearer away from shore. Nevada notes that harmful material may not always be visible. Carry enough drinking water for people and animals, and never use recreational water for drinking or food preparation.
Fishing and Boating Require Different Checks
The park guidance says to rinse fish with clean water at a fish cleaning station before eating them. Clean fish carefully and discard the guts, following current state and park directions. Avoid handling a catch in visible scum and wash hands with clean water before eating or preparing food.
For a launch day, separate facility status from water health. Confirm that the ramp or marina is operating, then inspect for algae and review the park alert. A launch can be accessible while swimming, splashing or high spray activity near a bloom remains a poor choice.
Travelers using an RV base can compare nearby options in Deep Arrival’s Laughlin campground guide or Bullhead City campground guide. A flexible base makes it easier to switch to a land activity without forcing contact with questionable water.
If a suspected bloom appears, the National Park Service asks for a wide photo showing the beach and landscape, a close photo, the location name and GPS coordinates when available. Report it without entering the water or touching the material. The park lists [email protected] for reports.
No Fixed End Date Makes Rechecking Essential
The alert does not name a reopening time because there is no blanket closure to lift. It remains a live advisory tied to current algae presence and water conditions. Call Lake Mead National Recreation Area at 702 293 8990 for updates, then check again at the exact shoreline.
Harmful blooms are most common at the recreation area from August through December, though they can occur at other times. Warm, calm and sunny conditions can help algae concentrate in coves. A cooler morning or a windy afternoon can change where material appears without proving the risk has ended.
Restore swimming or close contact only after current official guidance and the conditions at the access point support it. If the online alert, a posted sign and the water itself do not agree, use the most cautious signal. A dry hike, viewpoint or town activity is a better fallback than trying to judge toxicity at the shore.
| If you… | What to do |
|---|---|
| Planned to swim at Nelson’s Landing or Cottonwood Cove | Check the active park alert and avoid contact wherever algae is present. |
| See scum, mats or discolored water | Keep people and pets out, avoid spray and report the suspected bloom. |
| Have children or pets | Use a dry activity and carry clean drinking water rather than testing the shoreline. |
| Plan to launch a boat | Confirm facility status separately, then avoid visible algae and high spray nearby. |
| Need a current status answer | Call the park at 702 293 8990 and inspect official signs on arrival. |
The exact area is the first gate. Nelson’s Landing and Cottonwood Cove are the two locations named in the current alert.
Visible algae is the contact gate. Stay out when scum, mats or discoloration appears, even if a facility is open.
Children and pets raise the caution level. Choose a dry backup because accidental swallowing can make exposure more serious.
A live park update is the return gate. There is no fixed expiration date in the current alert.
Where was harmful algae found at Lake Mohave?
The active National Park Service alert names Nelson’s Landing and Cottonwood Cove, where harmful algae was confirmed in recent water samples.
Is all of Lake Mohave closed?
No blanket lake closure is stated. The park recommends limiting body contact at the named areas when algae is present and avoiding any visible bloom.
Can a dog swim near a harmful algae bloom?
No. Keep pets away from suspicious water and shoreline scum because animals can become seriously ill or die after ingesting toxins.
When will the Lake Mohave algae alert end?
The current alert provides no expiration date. Call the park at 702 293 8990 and review the live notice before restoring water activities.
