Excherichia Coli, commonly called E-Coli, is a rod-shaped bacterium that can cause serious illness in humans. Common routes of transmission include unhygienic food preparation, and contamination due to manure in contaminated water.
Since natural bodies of water attract animals, espeically birds it is common to have some level of fecal matter (manure) in a natural body of water. When levels of manure reach higher levels the level of E-Coli found in the water can rise and the risk of illness increases.
The City of Storm Lake and the Iowa Department of Natural Resources do testing (in Storm Lake testing is generally done by the City of Storm Lake). Results of the testing can be found on DNR