Be Aware: Stay Safe Around Denver’s Waterways, While Outdoors

Denver Department of Public Health & Environment offers tips for a safe and healthy summer ~

DENVER – The hot weather may have you craving a dip into one of Denver’s lakes or waterways or spending time in the outdoors unprotected from biting bugs. The Denver Department of Public Health & Environment (DDPHE) wants to be sure all Denverites stay safe and healthy while enjoying summer activities.Recreationists should keep in mind the dangers of potentially toxic blue-green algae and E. coli before they or their pets dip a toe or paw into our natural bodies of water.

Be Aware of Blue-Green AlgaeBlue-green algae has been detected in waterways in and around Denver. The cyanobacteria can cause neurological problems and liver failure in dogs, cats, livestock, wildlife, birds, and fish and humans. Water containing the toxic algal blooms look like pea-green paint or slime on the surface. It typically develops when the weather has been warm (over 75 degrees) and sunny. DDPHE this week posted caution signs about blue-green algae along Bear Creek within the city. Signs warn visitors not to let their pets in the water or drink it.DDPHE environmental analysts say Bear Creek water from Bear Valley Park through Bear Creek Park and likely onto the South Platte confluence contains blue-green algae. However, at the time of testing on Monday, July 18, toxins were not at levels that are a risk to public health. The blue-green algae source is Bear Creek Reservoir (approximately 2.5 miles upstream of Denver) which discharges to the creek, flows a couple miles through Lakewood and eventually into Denver. Denver residents should be aware that conditions could quickly change with consistently hot temperatures and continued release of blue-green algae-laden waters from the reservoir in the days ahead.

  • If your dog gets into a harmful bloom, rinse your pet off immediately with fresh, clean water. And, if you’ve been in contact with the bloom, immediately wash with soap and water.
  • If your pet has been poisoned by the algae, it’ll show symptoms anywhere from 15 minutes to several days, including diarrhea or vomiting, weakness or staggering, drooling, difficulty breathing and convulsions or seizures. Take your pet immediately to an emergency veterinarian.

The city is still working to resolve a blue-green algae bloom at Duck Lake in City Park, initially identified June 24. Denver Parks & Recreation (DPR) is using herbicide and aerating the lake and will remove posted “caution” signs when the bloom and potential for toxins is mitigated.Protect Yourself from E. coliRecreationists should also pay attention to elevated levels of E. coli in rivers that run through the city, including the South Platte, Cherry Creek, Bear Creek and Westerly Creek.The quality of this water is poor for those who want to recreate in it. The increase in E. coli is common during the summer and fall months. You can see the most recent E. coli testing results here.DDPHE does not recommend wading or playing in city lakes and streams since they receive runoff from streets, yards, parks and discharge from industry and wastewater treatment plants that can make you sick. But if you choose to immerse yourself in this water, here are tips to keep you safer:

  • Do not enter the water if you have cuts or open sores on your body.
  • Do not enter the water if it has an odd color or looks as if it’s experiencing a severe algae bloom (sometimes resembles green paint).
  • Wait 72 hours after a storm to enter the water. Street runoff is one of the largest pollution sources in Denver’s lakes and streams. Waiting allows bacteria levels to return to safer levels.
  • Wash your hands before eating.
  • Avoid swallowing the water, or areas where water is not flowing, areas with trash, oil slicks, scum, or water near flowing storm drains.

Fight the Bight – Mosquito SafetyWater is the source for another hazard in Denver and elsewhere, mosquitos.Humans can contract West Nile virus through a bite from an infected mosquito. As of now, the Colorado Department of Public Health & Environment has not reported a single human case of the deadly virus this year in the state.There were 175 cases in Colorado last year, representing the largest number of cases in 18 years.You can best protect yourself from mosquito bites through prevention and eliminating stagnant water where mosquitoes breed:Prevention Tips:

  • Limit activity outdoors at dusk and dawn.
  • Wear protective clothing like pants and long sleeves when outdoors.
  • Wear mosquito repellant containing DEET, picaridin, IR3535, or lemon eucalyptus oil.

Eliminate Mosquito Breeding Sites:

  • Remove standing water from around your home. Wheelbarrows, birdbaths, tires, gutters, containers/buckets, large divots in turf, and other places where standing water can accumulate are good places for mosquitos to breed.
  • Don’t overwater your yard so it pools on lawns and sidewalks.
  • Fix leaking irrigation systems.
  • If you do have pooling on sidewalks, street gutters, disturb it regularly with brooms.
  • Properly maintain fountains and swimming pools to ensure circulation or drain and cover if not in use.

Mosquito-Proof Your Home:

  • Install screens on windows and doors.
  • Incorporate xeriscape, with smaller turf lawns, in your yard to further reduce the number of mosquitos.

Mosquitoes generally remain active throughout the summer until September or until colder nights set in with temperatures in the 40s.It can be tempting. Hot weather can entice you to indulge in risky activities like soaking in tainted waters or spending the early mornings or evenings outside without protecting yourself from mosquitos. DDPHE hopes you’ll make smart choices this summer to safeguard yourself and your neighbors.

The Denver Department of Public Health & Environment (DDPHE), Denver’s nationally accredited public health agency, empowers Denver’s communities to live better, longer. The divisions of DDPHE are: Administration, Animal Protection, Community & Behavioral Health, Environmental Quality, Office of the Medical Examiner, and Public Health Investigations. In partnership with Public Health Institute at Denver Health, DDPHE provides quality public health services to the City and County of Denver. For more information about DDPHE, visit or follow us @DDPHE

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