North Iowa Outdoors: Study Says Beaver Dams Impact Water Quality and Quantity

Researchers at Iowa State University are studying beavers and the dams they build to determine what impact they may be having on the state’s fragile system of watersheds. The study’s name is the question they hope to answer, “Beavers: Superheroes for Water Quality?” Billy Beck, an ISU professor of natural resource ecology and management, says it’s still early in the three-year study, but they’re already starting to see some fascinating results.

Beck, who’s also an ISU Extension and Outreach forestry specialist, says beavers were hunted to near-extinction in Iowa more than a century ago but have since rebounded. Some farmers and landowners may be annoyed by the nocturnal rodents because of the flooding caused by their dams.

Beavers rarely just build one dam, it’s usually a whole string of dams, so Beck says they’re carefully testing the water in multiple areas.

Early findings indicate that nitrate levels are being reduced by beaver dam chains at the rate of one-to-two parts per million.

The study, supported by the Iowa Nutrient Research Center, is looking at beaver dams in north-central Iowa, including along Prairie Creek near Fort Dodge and along Caton Branch, near Woodward. Beck says there’s been much more study in the Pacific Northwest of beavers and their impacts, especially on fish populations, but little is known about them in the agricultural landscape of Iowa.