As fall begins, tourists planning to enjoy Missouri waterways and the sights of colorful fall foliage should take precautions due to reports of water contamination.
An analysis by the Environment America Research & Policy Center of water quality data collected in 2024 and 2025 found that 85% of Missouri’s recreational waterways had potentially unsafe levels of fecal contamination on at least one day of testing. At 70% of locations, potentially unsafe levels were recorded on at least one in four days of testing.
The locations with the most persistent risks were Truman Lake in Benton County, Sycamore Creek in Newton County and Grand Glaize Greek in St. Louis County. In Columbia, Finger Lakes State Park had unsafe levels on one of its 30 test days.
During the recreational season, the Missouri Department of Natural Resources samples the water at all designated swimming beaches in the Missouri state park system on a weekly basis. Individuals interested in checking the status of the waterways before arriving at the parks can use the department’s public beach map to determine E. coli levels.
According to MU Extension Water Quality Specialist Dan Downing, common sources of E. coli include humans, waterfowl, deer and other wildlife. Failing, leaking, or non-existent septic systems and leaking sewer pipes can contribute to fecal coliform found in ambient water. Common methods of treatment to kill coliform include chlorination, ozonation and ultraviolet light exposure.
Excess E. coli contamination can in part be prevented by ensuring septic and sewer systems are well maintained and adequate to fit the needs of those using them.
Downing notes that many types of water contamination are naturally occurring.
“The naturally occurring pollutants that we see, sometimes people don’t even think of them as polluting. For example, soil erosion carries with it anything that’s attached to it and organic matter like leaves and sticks,” Downing said. “That could bring anything from chemicals that we put out for beneficial uses that end up where we don’t want them, to bacteria and microorganisms.”
In late summer, a common sign of water pollution is large algae blooms in ponds and small waterways, which Downing said is typically due to elevated levels of phosphorus. Phosphorus can originate in leaching from septic systems, livestock manure and chemicals applied to plants.
While many forms of algae are harmless, if unsightly, some can be harmful. Blue-green algae, also known as cyanobacteria, can release toxins that are hazardous to pets and humans. Downing says a key form of prevention is limiting the supply of phosphorus these algae need to grow.
For individuals who are looking to limit their own impacts on water quality and the environment, Downing shared advice for safe usage. This included doing soil testing to ensure that there is not over-application of chemicals like nitrogen, phosphorus and potassium.
“Don’t overly overdo it, because anything that doesn’t get taken by the plant has a potential of moving off-site and into lakes or streams,” he said. “If we overuse chemicals, or do not use the right chemical to get the job done, we run the risk of those things ending up in our water supply.”
It can also be helpful to maintain ground cover, like grasses, so that loose soil is less likely to make it into waterways.
“If we do our best to minimize inputs, then hopefully in the long run that pays off and we preserve water supplies to keep things on the good side,” Downing said.
