By Hailey Murphy, S.C. Sea Grant Consortium.
Undergraduate research assistant Jack Cuneo and graduate research assistant Ibrahim Busari, Clemson University, collecting sediment core samples using a universal sediment corer, and on-site water quality measurements using proDSS YSI water quality meter in a residential stormwater pond in Charleston, South Carolina, in January of 2024. Photo credit: Erica Hussey/S.C. Sea Grant Consortium.
Are South Carolina’s coastal stormwater ponds aging out of peak performance as a water quality control measure?
For over 30 years, South Carolinians have increasingly relied on an abundance of stormwater ponds to mitigate the effects of flooding; provide water quality control by containing runoff, excess nutrients, and sediments; and add aesthetic and recreational amenities for residents and visitors.
Recently, pond owners have experienced increased challenges with algal blooms. Harmful algal blooms may cause health issues for residents and pets, lead to fish kills, and affect property values.
Blooms occur due to the buildup of runoff and nutrients, such as phosphorus and nitrogen from sources such as fertilizers and car exhaust, that encourage the rapid growth of algae and phytoplankton. We know these nutrients accumulate in our stormwater ponds, but how does phosphorus behave within these ponds over time? Understanding how phosphorus is distributed through the water column and stored in benthic sediment at the bottom of the pond in newer versus older ponds, and in different seasons, may help explain the rise of harmful algal blooms and inform stormwater pond management solutions.
This is the focus of a Consortium-funded research project entitled “On Borrowed Time: Age as a Predictor of Phosphorus Mobility in Coastal Stormwater Ponds and Implications for Management,” led by Principal Investigator Debabrata Sahoo, Ph.D., P.E., P.H., Associate Professor in the South Carolina Water Resources Center and College of Agricultural Sciences at Clemson University.
Graduate research assistant Morolake Fatunmbi, Clemson University, wearing protective gloves carries stormwater pond sediment and water samples. Photo credit: Erica Hussey/S.C. Sea Grant Consortium.
Co-Principal Investigators include:
- Erik Smith, Ph.D., Manager, North Inlet – Winyah Bay National Estuarine Research Reserve; Research Associate Professor, Baruch Institute for Marine & Coastal Sciences, University of South Carolina.
- Amy Scaroni, Ph.D., Assistant Professor, Clemson Baruch Institute of Coastal Ecology and Forest Science.
- Guinn Wallover, Water Quality and Environmental Program Specialist, Mount Pleasant Waterworks.
This project is supported by partnerships with North Inlet – Winyah Bay NERR, Baruch Institute for Marine & Coastal Sciences at the University of South Carolina, Mount Pleasant Waterworks, and Clemson’s Baruch Institute of Coastal Ecology and Forest Science.
Throughout the project timeline (2022–2024), researchers aimed to assess the influence of the age of residential stormwater ponds on internal sediment phosphorus dynamics, determining whether benthic pond sediment acts as a source or sink (storage) for phosphorus in the water column. The team hypothesizes that over time, pond sediment is less able to absorb and store phosphorus and instead begins to release phosphorus back into the water column. This could be caused by increased runoff containing phosphorus and fewer replenishing sediment deposits from the watershed entering the pond.
So far, the project team has identified residential ponds in coastal urban areas across the eight coastal counties suitable for the study; collected winter and summer water quality and benthic sediment samples from the ponds; conducted laboratory extractions and EPC0 (Equilibrium Phosphorus Concentration) data analysis; and have completed comparative statistical analyses.
The study area spans South Carolina’s 8 coastal counties. From north to south: Horry, Georgetown, Berkeley, Charleston, Dorchester, Colleton, Beaufort, and Jasper.
Next, the team aims to deliver their findings to stakeholders through written publications, including the Land Grant press, their project report, and other scholarly articles; digital publications such as the Consortium’s website; and present at the S.C. Water Resources Conference, the S.C. Association of Stormwater Managers, and other regional stormwater pond management conferences, and incorporate the results into an Extension workshop to inform stormwater pond management recommendations for pond owners, pond managers, engineers, and stormwater managers.
Graduate assistants (Ibrahim Busari, Jack Cuneo, Morgan Chaudry, and Morolake Fatunmbi) collecting stormwater pond sediment core samples using a universal sediment corer and on-site water quality measurements using proDSS YSI water quality meter. Photo credit: Erica Hussey/S.C. Sea Grant Consortium.
For more information, check out the Consortium’s stormwater pond programming across the state. You may also contact Debabrata Sahoo, Ph.D., P.E, P.H., Associate Professor in the South Carolina Water Resources Center and College of Agricultural Sciences at Clemson University.