Why does foam form in rivers

The reason for this is because of something called the Marangoni effect. You might have seen this demonstrated in middle school science class with a bowl of water sprinkled with pepper and a drop of soap.

The reason that happens is that the soap creates a spot with lower surface tension, and the water flows away from that spot.

For complicated physics reasons that I only half understand, this same effect stabilizes bubbles and makes foam possible. Did we say that yet? Yes, we did. Yeesh, Brendan. Search Query Show Search. About NHPR. Show Search Search Query.

Play Live Radio. Next Up:. During soil erosion events or from human activities, such as gravel washing. Is foam harmful?

Foam is usually harmless. In fact, only 1 percent of the foam you see on a waterbody is the actual foaming agent; the rest is air and water. However, excess foam is sometimes the result of too much phosphorus in the water. Although phosphorus in an important plant nutrient, it is not found abundantly in nature and too much of it is indicative of pollution from human activities.

Excessive phosphorous can result in nuisance algae blooms, fish kills due to low dissolved oxygen from decomposition processes, and irregularities with the water's taste and odor. How can I tell what kind of foam it is? Natural foam usually: appears as light tan or brown in color, but may be white; smells earthy, fishy or has fresh cut grass odor; can occur over large areas and accumulate in large amounts, especially on windward shores, in coves and eddies; and dissipates fairly quickly, except when agitated as in high wind conditions.

Unnatural foam from human activity usually: appears white in color; gives off a fragrant, perfumed or soapy odor; and usually occurs over small area, localized near source of discharge. It will often be found near the point of discharge. Organic rich foam trapped by a tree and natural debris on the East Branch of the Ausable River.

To minimize human-made foam , reduce the use of synthetic chemicals on outdoor surfaces and, where you do use them, follow label instructions carefully. Also, make sure your septic system is properly maintained. Most residents of the Ausable watershed rely on private septic systems. Wastewater leaving your house from the shower, toilet, sink, clothes washer, and dishwasher all enter your septic system, carrying chemicals, solids, grease, dirt, and pathogens. A properly designed and maintained septic system treats and disposes of this wastewater, preventing contaminants from entering our natural waterways.

Sign-up for our e-newsletter to get weekly updates on the latest stories from the Ausable River Association. We greatly appreciate our business partners for their support and commitment to the health of the Ausable River watershed. To find out how you can partner with the Ausable River Association, click here. Search form Search. Natural foam on the Ausable River.