Title: Are Your Ponds Serving their Water Quality Function?
- John S. Gulliver, professor emeritus, Civil, Environmental and Geo- Engineering, resident fellow at the Institute on the Environment, and St. Anthony Falls Laboratory, University of Minnesota.
- Poornima Natarajan, Research Associate, St. Anthony Falls Laboratory, University of Minnesota.
Stormwater ponds and wetlands across a wide variety of characteristics (e.g., watershed history, age, size, depth, aquatic vegetation) are used to treat stormwater to remove a significant portion of sediment and associated pollutants in runoff (e.g., phosphorus, nitrogen, hydrocarbons, and metals) prior to the runoff being released downstream. An important contemporary management issue is that some stormwater ponds appear to be less effective than expected or originally intended in phosphorus retention, a key function of these stormwater best management practices (BMPs) in urban environments. There is recent evidence that many old stormwater ponds are releasing phosphorus from bottom sediments at high rates and likely exporting phosphorus to downstream surface water bodies. The potential for phosphorus re-release from accumulated sediments in ponds and factors related to climate, watershed, pond characteristics that regulate phosphorus release or burial are important in controlling phosphorus dynamics in ponds. Retention of phosphorus is critical because phosphate, a dissolved form of phosphorus, sustains algal and cyanobacteria growth and causes a wide range of water quality impairments in the ponds and downstream waters including algal blooms, excess floating plants, taste, and odor problems.
After a short description of our research work since 2016, this presentation will describe two items of interest to watershed managers:
- A Pond Assessment Tool, developed to identify and evaluate ponds at risk for poor phosphorus water quality and export of phosphorus to receiving water bodies. It results from data analysis of 230 water bodies and detailed water quality and sediment analysis of 20 ponds, which formed the basis of the Pond Assessment Tool tool with statistical analysis of field data and regression models for predicting pond TP, pond anoxia, and sediment release.
- Recommendations for stormwater pond maintenance and wetland management based on project results and data synthesis of construction and maintenance costs and runoff storage/settling alternatives.
Date and Time: Thursday, June 1, 2023, 12 - 1pm CDT
Hosted by the City Engineers Association of Minnesota.
Online: Zoom Link