Foamy rivers caused by decaying organic material in snow runoff

IOWA CITY -- White foam stacked several feet high below the Burlington Street dam on the Iowa River in Iowa City isn't caused by a shampoo spill.

It's a natural result of melting snow that carries decaying organic material, such as dead leaves or grass, said Doug Schnoebelen, a water quality specialist with University of Iowa IIHR – Hydroscience & Engineering.

"People see all the foam and think someone is doing something to the river, but it's pretty natural," Schnoebelen said Monday. "It's the highest I've seen in a while.”

With unofficial snow totals of about 40 inches in parts of Eastern Iowa, there's a lot of runoff going into Iowa's streams and rivers. The decaying debris reduces the surface tension of the water, allowing in more air and creating bubbles, Schnoebelen said.

Foam appears on other rivers, such as the Mississippi River, where Schnoebelen is director of the Lucille A. Carver Mississippi Riverside Environmental Research Station north of Muscatine. But the effect is more pronounced in areas with dams.

Organic compounds "act like a surfactant, like soap bubbles, and makes the water more slippery,” Schnoebelen said. “So when it goes over the dam, it gets more air.”

Peaks of foam visible on the Iowa River Monday will likely decrease as the week goes on, he said.