Stormwater Pond Maintenance and Wetland Management for Phosphorus Retention

Status:  Complete
Report Date:  07/26/2023


Local governments manage stormwater in wetlands and both natural and constructed stormwater ponds. The ponds reduce flood risk in communities and retain pollutants from fertilizer, animal waste and other products that are found in stormwater runoff. One of these pollutants—phosphorus—sinks to the bottom of the pond and remains in the pond sediment. As ponds age, however, the vegetation, water depth and other pond characteristics may change. As a result, phosphorus may be released from the sediment and potentially enter streams and lakes. A new tool can help local governments better manage these ponds to retain phosphorus. Leveraging previous research, investigators sampled and monitored several ponds over two years. In addition to sediment testing in the laboratory, they analyzed both the collected data and data from the past 15 years from approximately 230 ponds in the Twin Cities metro area. The identification of pond characteristics that correlated with high phosphorus levels led to the creation of a pond assessment tool. Local managers can use the tool to understand which ponds may be at highest risk of releasing phosphorus and where managers should focus remediation efforts or use other management practices to ensure the ponds are performing as designed.

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