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Water Quality Program

Welcome to the home of DDPHE's Water Quality Program!

DDPHE has been monitoring the quality of water in Denver’s lakes and streams for more than 45 years. Over that time, the program has grown to include many other important details of water quality. You can learn more about what we do by exploring the topics below.

Water Quality in Lakes and Streams

Denver’s goal is to have fishable and swimmable waters in all our lakes and streams by 2020. Denver’s Departments of Public Health and Environment, Public Works, and Parks and Recreation are all working hard to ensure the City meets that goal. Here are a few things the City is doing to improve water quality in its streams and lakes:

  • The City has developed a program to improve storm water facilities in 10 priority areas with the intent of protecting water quality in the river. To date, the program has successfully reduced the amount of bacteria entering the South Platte River from most of the basins. It is still too soon to tell how those reductions have affected water quality in the South Platte River.
  • The City has identified areas where more facilities are needed to ensure storm water runoff is adequately treated to remove sediment, trash, and other pollutants. City staff are using this information to develop a plan to add water quality treatment facilities in those areas.

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 you sick.

DEH does not recommend swimming, wading, or playing in City streams or lakes. Swimmers are encouraged to use the swimming facilities provided by the Denver Parks and Recreation Department 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 tips to help keep you safe:

  • Wait 72 hours after a storm
    • 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.
  • Avoid waters near flowing storm drains
    • Water coming out of storm drains may contain bacteria or other pollutants that can make you sick.
  • Avoid areas where the water is not flowing
    • The lack of flow allows bacteria to accumulate to levels that can make you sick.
  • Avoid areas with trash and other signs of pollution such as oil slicks or scum
    • These signs may indicate the presence of disease causing microorganisms.

Denver Water Quality employee sampling water at Sloan's LakeDDPHE samples most of the streams and many of the lakes in Denver at least once a year. Sampling results 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. DEH posts information on the latest water quality results for the following sites on the map below and on our Facebook page. The map includes photographs of many of the sampling locations.

  • 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);
  • Sloans Lake (sampled every other week, May-October);
  • Westerly Creek near the playground in great Lawn Park (sampled once or twice a month from May to October);
  • 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.  

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

The Denver Department of Public Health and Environment’s Environmental Quality Division monitors the streams and lakes within the City and County boundaries. Streams are monitored year-round while lakes are typically sampled once per year during the summer. Results from monitoring are summarized in annual reports.

The most recent versions of our reports are available by clicking on the links below. For additional information or to get copies of older reports, please contact the City and County of Denver by calling 3-1-1 and requesting the Division of Environmental Quality.

From time to time events will occur that require advisories be posted on City lakes or streams.  Information about those advisories can be found here.


  • There are no reports of spills at this time.

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. 

Fish Kills

  • There are no advisories at this time. 
  • There are no other advisories at this time.

Bluegreen algae is a type of algae-like bacteria that generally grows in lakes, ponds and streams when the water is warm and enriched with nutrients like phosphorous or nitrogen. When environmental conditions are right, the algae can grow quickly. The blooms are often reported by area residents and visitors, as they are quite visible when they float to the surface and form algae slicks, also known as “blue-green algae bloom.”

Bluegreen alga can produce several toxins that can make people, pets and other animals sick. People can experience skin rashes and lesions when skin comes in contact the algae. Ingesting water can cause vomiting, diarrhea, or liver failure in extreme cases. Animals that ingest the water can experience skin irritation or lesions, vomiting, and nervous and digestive system disorders.

Sloan’s Lake is currently experiencing high levels of algae. People and animals are cautioned to avoid contact with the water around the algae slicks, particularly near the marina and boat ramp and dock, which has among the highest concentrations of algae.

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

For questions, call 311 (720-913-1311). 

How Can I Improve Water Quality?

Keeping Denver's lakes and streams clean requires everyone’s help. Runoff carries with it oil, chemicals, pesticides, fertilizers, pet waste, debris and sediment directly into the storm sewer, stream, or lake without treatment.

You can help by taking a few precautions and changing habits in small but noticeable ways. Every individual action adds up, and every individual can make a difference.

Volunteer Opportunities

Here are a couple of places were you can find out about opportunities to help Denver keeps its lakes and streams clean:

  • Denver’s Department of Parks and Recreation keeps a list of volunteer opportunities on their web page
  • DDPHE's Water Quality Program occasionally posts volunteer opportunities on our Facebook Page.

Here are some things you can do to help keep our streams and lakes clean:

  • Take a pledge to protect Denver's leak, steams and rivers.
  • Throw away your trash in a trash receptacle, not on the ground or in the gutter.
  • Pick up after your pet and place the waste in a trash receptacle.
  • Apply fertilizer and pesticides in accordance with manufacturer's recommendations.
  • Don't apply fertilizer and pesticides before a storm.
  • make sure your vehicle is properly maintained to minimize leaks and drips
  • Wash your vehicle at a car wash, not in the driveway or street..
  • Dispose of household and hazardous chemicals (such as paint, pesticides or vehicle oil) properly. For information on disposal, visit Denver's Household Hazardous Waste Collection Program or call to schedule a pick up at 1-800-HHW-PKUP (800-449-7587).
  • Dispose of unwanted medicine and prescriptions at a medication take back event. To find the next take back event near you or to find medication disposal locations, visit Colorado AwareRX
  • Volunteer to adopt a trail or park near a steam or lake, or participate in an event like RiverSweep. To adopt visit Denver Parks and Recreation volunteer site, or volunteer at one of The Greenway Foundation's and Groundwork Denver's river clean up events.
  • Report any of the following unusual conditions in Denver's lakes and streams by calling 311:
    • A change in color of the water
    • An unusual or foul odor
    • Suds when there has not been recent precipitation
    • Any unusual-looking substance discharging from a storm outlet
    • Illegal dumping activity
    • Unusual discharges from construction sites or industrial sites
    • Large number of dead or dying fish or crayfish

Other Topics

Trash is the most visible pollutant found in our streams. In a typical year, the Urban Drainage and Flood Control District collects around 100 tons of trash from the streams in Denver.

In 2012, the City’s Environmental Health and Parks and Recreation Departments partnered with The Greenway Foundation and several other organizations to address trash in the City’s streams. The goal of the partnership is to collect information about the types and extent of trash in Denver’s streams and to understand people’s knowledge and attitudes towards littering.

Efforts to understand the types and extent of trash began with trash inventory and clean up events on the South Platte River in 2012. The inventories consisted of collecting and categorizing trash at several locations along the banks of the South Platte River and bagging it for proper disposal. The most common types of trash collected were cigarette butts and packaging, food packaging, plastic bags, Styrofoam, and paper and cardboard. See a Summary of the results. A follow up survey was conducted on Cherry Creek in 2014. The results of the survey were similar to the results from the South Platte River.

The project team also conducted telephone surveys to gauge the public’s understanding of trash in streams and attitudes towards littering. The surveys identified a number of areas where knowledge and attitudes towards littering could be improved.

Information from the study was used to develop an information and education plan which is intended to change people’s attitudes and behaviors towards littering.

Over the past decade, DEH staff have observed dead and dying birds in the City’s lakes. The observations occur in the hottest months of the year, typically between late June and September. Two possible causes for the dead and dying birds have been identified: Avian Botulism and West Nile Virus.

Avian botulism affects waterfowl and shorebirds that ingest a toxin which is commonly found in sediments at the bottom of lakes. Birds suspected of having avian botulism often have trouble holding their necks and heads up and may also appear to struggle to swim across the water. Unfortunately, death by drowning is often the end result. 

City staff routinely monitor for potential signs of avian botulism during warmer weather and respond by removing bird carcasses and working with rescue organizations to help sick birds as quickly as possible. Sick birds stand a good chance of surviving when promptly treated by local bird rehabilitators such as Wild B.I.R.D. or the Denver Zoo.

West Nile virus is a potentially serious disease which is transmitted by mosquitoes. Mosquitoes become infected after biting an infected bird and then may pass the virus on to other birds, humans, or animals. Mosquitoes carry the highest amounts of virus in the early fall, but the risk of disease decreases as the weather becomes colder and mosquitoes die off. To most people, the symptoms are similar to those of avian botulism. Please contact Denver Department of Public Health and Environemtn by calling 3-1-1 if you see multiple sick or dead birds in your neighborhood.

Click here to learn about DDPHE's Mosquito Control Program.

Fish kills are occasionally observed in Denver’s streams and lakes. A fish kill is a localized die-off of fish populations. There are many causes of fish kills, but oxygen depletion is the most common cause. Oxygen depletion may be due to factors such as drought, algae blooms, overpopulation, a sustained increase in water temperature, or extended periods of ice cover on shallow lakes.

If we are aware of a recent fish kill, we will post information on recent fish kills in Denver streams or lakes in the Public Advisories section of our web page.

If you observe dead fish in any of Denver’s streams or lakes, please report them by calling 3-1-1. 

In 2014, the City’s Department of Parks and Recreation began work on an ambitious plan to improve the Parks along Denver’s river corridor. Since then, improvements at the confluence of Weir Gulch and the South Platte River, Johnson Habitat Park, and stretch of river between Overland Pond and Pasquinel's Landing were completed. Work to improve Pasquinel's Landing, Grant Frontier Park, and Confluence Park also started. Plans for all the parks include features that will improve water quality in the South Platte River. DDPHE is working with the Parks design team on a number of issues related to the park improvement projects including environmental site assessments, ensuring design features improve habitat and water quality, and incorporation of education and outreach efforts related to water quality and recreation in urban waters.  

The City’s Department of Parks and Recreation has plans for improvements at many other parks along streams and lakes in Denver. For more details, visit Parks and Recreation’s Master Planning web page. More information on the River visioning process, including planning documents can be found on The Greenway Foundation’s Website.

Graywater is gently used water that comes from laundry machines, bathtubs, showers and bathroom sinks. For more information, visit 

Water Quality Map

How to use this map:

Icons are located at water sampling areas. A red icon indicates that the site is not safe for recreation. Clicking on the icon will open up a window with a photo of the area, a description of the site, and information related to the most recent sampling results.


Connect with Water Quality


Notice any unusual conditions in our lakes and streams? Call 3-1-1 or  Denver 311 online.

Comments/Questions? Email us at

Department of Public Health and Environment News & Information