Foam in Waterways

Where is the foam from?

It is common for organic matter naturally found in our waterways to decompose, releasing fatty molecules (lipids) that produce the foam we see on the surface of the water. This happens every year, usually during the spring runoff season, but it can also occur during periods of high precipitation and high temperatures in summer and fall months. The foam is most apparent at locations where the water is naturally agitated by flowing over rocks or discharging from pipes. The foam produced may be more than a foot deep!

This report of foam is most likely due to the recent localized rainstorms transporting fresh organic material into the waterway and subsequent high daily temperatures accelerating the natural process of organic decay, producing more visible foam than is typically seen this time of year.

Natural Foam vs. Illicit Discharge

Naturally forming foam appears as white to off-white and will have an earthy or fishy smell when rubbed between your fingers and will rapidly dissipate within 24 hours.  Foam that has a chemical or perfume-like smell and/or doesn’t rapidly dissipate could be the result of an illicit discharge. In these instances, the water will be sampled and the upstream inputs will be examined. For more information on this natural phenomenon, please contact your local municipality or the CSU Extension.

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