Beaver dams: A free conservation practice for water quality enhancement?

January 20, 2021 8:51 AM

A recently-funded study is kicking into high gear this spring, intent on investigating the water quality and quantity impacts of certain woody structures that are all-too-familiar to Iowa landowners—beaver dams. Beaver (Castor canadensis) activity (i.e., damming of streamflow) holds significant potential to impact water quality, specifically in-stream nutrient processing, through reduction of streamflow velocity and increase of water residence time within pools, trapping of sediment and organic material, raising of riparian groundwater tables, and restoration of channel-floodplain connectivity. Thus, dams may represent a “no-cost in-stream conservation practice” that provide compound benefits beyond water quality and quantity, such as enhanced aquatic and terrestrial wildlife habitat and increased riparian vegetation diversity.


What makes this endeavor unique and timely? Although numerous studies on the hydrologic and aquatic wildlife habitat (e.g., salmonid) impacts of dams have occurred globally, far fewer studies have focused exclusively on dam impacts to in-stream nutrient processing and watershed-scale nutrient loading. In addition, studies that investigate dam impacts to water quality and quantity in the agricultural Midwest, where watersheds frequently exhibit elevated nutrient loads, flashy hydrology, and stream channel incision, are exceptionally rare.

Beaver dam in summer, central Iowa

Photo 1: Everett Johnson (ISU Animal Ecology Senior) stands on the downstream side of an active beaver dam. Note the differences in stream channel width, water surface elevation, and water velocities upstream and downstream of the structure. Photo credit: Billy Beck, ISU Extension Forestry

The overall goals of the project are to identify and quantify key nutrient (e.g., N, P) removal processes associated with beaver dams in central Iowa, and estimate the potential impact of dams on watershed-scale nutrient loading within the agricultural Midwest. The study has been funded through the Iowa Nutrient Research Center (INRC), and long-term, this project aims to provide the Iowa Nutrient Reduction Strategy (INRS) Science Team with data that clarify the influence of the stream channel and processes associated with in-stream nutrient loss on watershed-scale nutrient loads.


An ISU Environmental Science graduate student has recently joined the team, and is tasked with leading the multi-disciplinary study which entails elements of forestry, hydrology, biogeochemistry, and fluvial geomorphology (i.e., how water shapes the Earth). In addition, undergraduate “spin-off” research projects seek to simultaneously investigate beaver impacts to riparian vegetation and aquatic habitat.


Have a dam, series of dams, or history of beaver activity on your central-Iowa property? If so, please contact Billy Beck (515-294-8837, to discuss potential for water quality monitoring associated with the structures. For additional information on this study, as well as other impactful INRC-funded efforts, check out the Projects Page and Water Quality Research Map located within the INRC website.