Other Water Quality Information

Trash and Litter

image of trash in Westerly Creek Trash is the most visible pollutant found in streams. In a typical year, the Mile High Flood Control District collects approximately 100 tons of trash from the streams in Denver. Studies conducted by DDPHE and The Greenway Foundation in 2012 found that the most common types of trash collected in the South Platte River were cigarette butts and packaging, food packaging, plastic bags, Styrofoam, paper and cardboard. 

Dead or Dying Birds

Over the past two decades, DDPHE 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

Avian botulism affects waterfowl and shorebirds that ingest a toxin which is commonly found in sediment 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. Leaving infected carcasses in and around the waterbody increases the spread of the disease. It's very important that all carcasses, birds and others, be removed.

For more information, visit USGS – Avian Botulism

West Nile Virus

West Nile virus is a disease 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 late August and September until the weather cools and mosquitoes die off. To most, West Nile virus symptoms in birds appear to be similar to those of avian botulism.

For more information, go to CDC’s West Nile Virus web page.

Please contact DDPHE by calling 311 if you see multiple sick or dead birds in your neighborhood.

Fish Kills

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. Oxygen depletion may be caused by drought, algae blooms, overpopulation, a sustained increase in water temperature, or extended periods of ice cover on shallow lakes. Other possible causes can include high or low pH values or viruses which are often specific to a particular fish species.

If you observe dead fish in any of Denver’s streams or lakes, please report them by calling 311.

Suds in Denver's Streams

It is fairly normal to see suds in an urban stream after a storm. The amount of suds may be significant if it has been a long time since it last rained (or there was snow melt).  Two common sources of suds are:

  • Surfactants washing off roadways that were deposited by vehicle emissions (exhaust); and
  • Naturally occurring surfactants from organic matter building up in gutters and along streams edges.

The amount of suds may increase in intensity depending on how long the dry period prior to the rain event (or snow melt) was. 


Roadways: Gasoline contains detergent additives intended to keep the engine components clean and running smoothly. The detergents are also called surfactants. As gas is burned, the surfactants are deposited as a waste product on streets and are then washed into nearby waterways during storm events. The result is suds, particularly downstream of drop structures and riffles where the surfactants get worked up. The problem tends to be worse after long dry spells and in areas with lots of impermeable surfaces (such as parking lots and roads).

Natural:  There are also natural surfactants in organic matter. As leaves and other organic matter break down, its primary components build up in gutters and along stream edges. The longer the dry period, the more natural surfactant material builds up. During storm events this material is washed into area waterways and makes suds. 

Other sources:  Other sources of suds include detergents from car washing (residential, commercial, or car sales lots), power washing of streets, lots, buildings, and sidewalks, business operations (i.e., restaurants and others with alleys), and window cleaning. Illicit sanitary wastewater connections from businesses and residences into the storm sewers. Storm sewers discharge directly to streams. 

If you see suds when there hasn’t been any rain or if the suds smell like a perfumed detergent, please call 311.

Mosquito Control

Denver’s Mosquito Management Program uses an approach designed to reduce public health concerns and provide information and education to residents and businesses to help them keep mosquito populations at a safe level.

Learn more about DDPHE's Mosquito Control Program.