Impacts of ecological diversity on bioretention cell performance during establishment in the midwest

A bioretention cell is a recessed area of vegetation designed to accept and treat stormwater runoff through infiltration into layers of plant roots and growing medium. The bioretention cell is just one example of a Stormwater Best Management Practice (BMP) which can be used in conjunction with or as an alternative to traditional stormwater practices. Bioretention cells facilitate water treatment through natural hydraulic processes. However, design limitations arise from the lack of understanding of the influence that ecological factors have on the function and longevity of bioretention cells. To understand the region-specific function of bioretention cells, a lysimeter study is being conducted at Kansas State University on using vegetation and soil microfauna native to the Midwestern United States. Specifically, the effect of earthworms and native Kansas grasses have on runoff treatment and hydraulic function will be examined. To compliment this study, the Comprehensive Bioretention Cell (BRC) model will be used to estimate impacts of earthworm activity and plant growth on infiltration rate. The BRC Model predicts how a bioretention cell will function under a single storm event. The BRC model does not inherently reflect the role that ecological succession has on cell performance, so soil input parameters will be based on the rates of macropore formation by earthworms and vegetation and the resulting macropore densities. Expected outcomes are that through interaction with plant roots and soil microfauna, stormwater volumes, peak flow rates, and pollutant concentrations will decrease. Observed field measurements will be used to validate the BRC model.