WaterDams play an important role in water pollution control

The Peninsular Dam, near Ypsilanti, Michigan // Source: commons.wikimedia.org

Sometimes, little things can add up to a lot. This is the message of a research studyon small dams, streams, and pollution by Steve Powers, a postdoctoral researcher in the University of Notre Dame’s Environmental Change Initiative(ND-ECI).

“Small dams, reservoirs and ponds trap water pollution, which provides an important benefit to water resources,” Powers said. “This is especially relevant in agricultural lands of the Midwest U.S., where there are lots of small, but aging, dams.”

A University of Notre Dame release reportsthat although small individually, the sum total of the small reservoirs and ponds have a global surface area comparable to that of all large reservoirs added together.

Powers and his fellow researchers showed in detail how a small, aging dam, which was more than 100 years old and located in agricultural Wisconsin, trapped water pollutants associated with fertilizer and manure runoff. They also showed an increase in downstream transport of nutrient pollution after the dam was removed, which occurred because of concerns about the dam’s safety.

“Many small dams are threatened by long-term structural decline and are also filling with sediment,” Powers said. “If we don’t better incorporate how small dams affect the movement of water and wastes through the environment, their benefit to downstream water quality could be lost. Meanwhile, legacy sediment and pollution currently trapped behind dams could release as dams lose their water storage capacity, fall apart or are removed deliberately.”

Powers notes that there is a crucial need to gain a better understanding of what small dams mean for our water quality before they crumble and disappear.

“I am continuing to work on the subject at a broader regional scale by looking at hundreds of stream and river monitoring stations throughout the Midwestern U.S. to detect signals of dams,” he said. “One current goal is to try and figure out which regions are most vulnerable to water quality changes caused by accumulation of sediment and phosphorus behind dams.”

The release notes that Powers is conducting his research as part of the ND-ECI’s Land Use Project. The ND-ECI conducts policy-oriented research designed to help policymakers manage environmental changes.

— Read more in S. M. powers et al., “Retention and transport of nutrients in a mature agricultural impoundment,” Journal of Geophysical Research-Biogeosciences118, no. 1 (March 2013): 91–103 (DOI: 10.1029/2012JG002148)