Recreating in Denver's Lakes and Streams

DDPHE samples streams and most public lakes in Denver at least once a year. Results from samples collected at the following locations are compared to criteria issued by the State of Colorado to determine if it's safe to be in contact with waters in Denver’s streams and lakes. The most recent results are posted weekly on our Water Quality Map / Dashboard (see below).

  • The South Platte-Cherry Creek confluence (sampled weekly, May-October and twice a month the rest of the year);
  • Bear Creek at the picnic shelter in Bear Creek Park (sampled weekly May through October);
  • Westerly Creek near the playground in great Lawn Park (sampled once a month from May to October);
  • Sloans, Berkeley, and Rocky Mountain Lakes (sampled monthly from May to October);
  • A number of other sites on the South Platte River and Cherry Creek are sampled monthly and sites on Bear Creek are sampled once a quarter year-round. 

Historic data from DDPHE’s stream sampling efforts can be found on the Denver Open Data Catalog (search for water quality data). Information about water quality in streams throughout the metro Denver area can be found in the South Platte Urban Waters Partnership’s Water Quality Assessment Tool

Notice:  Regardless of recent sampling results and posted advisories, people should always use caution when recreating in urban surface waters.

Recreate Safely in Denver's Lakes and Streams

Denver’s lakes and streams receive runoff from city streets, yards, parks, and discharges from industry and wastewater treatment plants. Sometimes pollution in the runoff and discharges, which includes bacteria such as E. coli, can make residents sick.

DDPHE does not recommend swimming, wading, or playing in city streams or lakes. Swimmers are encouraged to use the Denver Parks and Recreation swimming facilities throughout the city. Kayakers may also become ill from ingesting surface water. If you choose to enter one of the city’s streams of lakes, here are some safety tips: 

  • Runoff from City streets is one of the largest sources of pollution in Denver’s lakes and streams. Waiting at least 72 hours (3 days) after it has stopped raining provides time for bacteria levels to return to safe levels.
  • Try not to swallow the water, and if you’ve been in the water ALWAYS wash your hands before eating.

Things to Avoid

  • Waters near flowing storm drains - This water may contain bacteria or other pollutants that can make you sick.
  • Areas where the water is not flowing - The lack of flow allows bacteria to accumulate to levels that can make you sick.
  • Areas with trash and other signs of pollution such as oil slicks or scum - These signs may indicate the presence of disease-causing microorganisms.
  • Significant algae blooms that resemble green paint - These areas may have toxin levels that can cause skin irritation or physical problems for both humans and pets. 

Check out this infographic on how you and your dog can stay safe when recreating in Denver's streams and lakes:

Stay Safe Gfx 6-7.png
View an accessible PDF version of the above infographic(PDF, 711KB)
(en español(PDF, 413KB))

Although fishing is allowed in Denver's streams and lakes, we recommend catch and release fishing only.

E. coli in Denver

Public Notices

From time to time, events will occur that require advisories be posted on city lakes or streams. Long-term public advisories include:

Fish Consumption

Do not consume largemouth bass from Berkeley and Rocky Mountain Lakes due to elevated levels of mercury in fish tissue. Eating fish contaminated with mercury, a pollutant which interferes with the brain and nervous system, can cause serious health problems, especially for pregnant women and small children. First posted March 2006. Re-assessed in 2015 – advisory was maintained. Consuming fish from other streams and lakes is not recommended.

Bluegreen Algae

Sloan’s Lake typically has high levels of bluegreen algae during summer months as dry, hot weather makes bluegreen algae blooms more likely. People and animals are cautioned to avoid contact with the water around the algae slicks, particularly near the marina, boat ramp, boat dock, and the shallow perimeter between the boat ramp and boat docks. These areas typically have higher concentrations of algae. Find more information on the causes and risks of exposure to bluegreen algae in the section below.

Invasive Species

New Zealand Mudsnails have been found in the South Platte River. The New Zealand Mudsnail is an invasive species which competes with native fish populations. People fishing in the South Platte River are advised to clean their waders prior to moving to a different location on the South Platte River or to another stream. Visit the Colorado Division of Wildlife's webpage for more information on the New Zealand Mudsnails and how to properly clean waders to prevent spread.

Bluegreen Algae

Waterbody covered in bluegreen algae Bluegreen algae is a type of bacteria (cyanobacteria) that grows in still waters, mostly in lakes, ponds and wetlands. It can also be found in the backwaters of streams during dry periods when flows are low. Bluegreen algae thrives when the water is warm and enriched with nutrients (phosphorous and nitrogen), which are plentiful in urban waters. When environmental conditions are right, algae can grow quickly. Blooms become visible when they accumulate on the water surface and form algae slicks, often appearing as green paint.

Bluegreen algae can produce several toxins that can make people, pets and other animals sick. People can experience skin rashes and lesions when skin contacts the algae. Ingesting water can cause vomiting, diarrhea or liver failure in extreme cases. Animals that ingest the water can also experience these symptoms. 

If you or a pet come in contact with bluegreen algae, the algae should be washed off the skin or animal's coat thoroughly. If symptoms are being experienced, contact your physician or veterinarian immediately. 

Please contact the Environmental Quality Division with questions or concerns on bluegreen algae. The Environmental Quality Division can be reached by calling 311 (or 720-913-1311 from a mobile phone)