Poornima Natarajan1, Ben Janke1, John Gulliver1, Jacques Finlay1,2
1St. Anthony Falls Laboratory; 2Department of Ecology, Evolution, and Behavior; University of Minnesota
Logo for the LRRB
Logo for the Clean Water Land & Legacy Amendment
Logo for the Minnesota Stormwater Research Council
Motivation
Minnesota has thousands of stormwater detention ponds used to manage runoff volumes and treat stormwater by removing pollutants such as phosphorus before water enters downstream lakes and streams.
Many ponds are aging, filling in with sediment and organic matter, and being overgrown by vegetation within and around the ponds.
Photos of ponds covered in algae and overgrown vegetation
Many of these ponds have poor water quality: high phosphorus concentrations, with low dissolved oxygen conditions that promote release of phosphorus previously buried in the sediment.
Graph of Pond Water Mean Total Phosphorus (mg/L): Roughly 40% of Twin Cities Metro Area ponds with sampling data (n~200) have pond water TP levels exceeding avery stormwater runoff concentrations.*
*Finlay et al. (2024) wrc.umn.edu/leveraging-stormwater-resources
How do we develop a tool for stormwater managers and practitioners to easily and rapidly assess a large number of ponds for risk of poor phosphorus retention?
Acknowledgements
We gratefully acknowledge the cities and organizations contributing data to this project: cities of Bloomington, Chanhassen, Eagan, Eden Prairie, Edina, Minneapolis, Minnetonka, Roseville, Shoreview, Shorewood, St. Cloud, and St. Paul; Minneapolis Parks and Recreation Board; Capitol Region Watershed District Riley-Purgatory-Bluff Creek Watershed District, Ramsey-Washington Metro Watershed District, WSB Engineering, South Washington Watershed district, Washington Conservation District, and the Three Rivers Park District
Funding provided by the Minnesota Stormwater Research Council (www.wrc.umn.edu/msrc) and the Minnesota Local Road Research Board (lrrb.org).
Graphic showing Many Processes Affect Phosphorus in Ponds including, watershed inputs, floating plants, sediment characteristics, tree canopy, emergent plants, algae, pond outputs, and internal processes.
Graphs of key drivers of pond phosphorus and dissolved oxygen from recent studies showing Phosphorus is higher in ponds with lower dissolved oxygen, greater free-floating plant cover leads to lower dissolved oxygen, older ponds contain higher phosphorus in their sediment, and high mobile phosphorus mass in sediments relates to high sediment phosphate release rates.
Logo of St. Anthony Falls Laboratory, UMN
Table of Development of a Spreadsheet Tool showing Tool 1-A: Screening Tool using Risk Indicators and Predictive Tools using Multivariate Regression Models, Tool 1-B: Prediction of Pond Phosphorus Concentration, Tool 2: Prediction of Pond Dissolved in Oxygen, Tool 3: Prediction of Sediment Phosphate Release Rate
Download the Report, Tool, and a tutorial at https://wrc.umn.edu/projects/pond-tool