Wetlands targeted for water quality improvement are strategically located and designed to remove nitrate from tile-drainage water from cropland areas.
Performance of installed wetlands is dependent on the wetland-to-watershed ratio, meaning how large is the wetland compared to the watershed area above the wetland. The larger the wetland, the greater the percentage of nitrate-N and P removal. From reported values from multiple wetlands in Iowa, the nitrate concentration reduction averages 52%. Wetlands also provide improved aesthetics and Iowa game and waterfowl habitat.