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College of Charleston dashboard shows groundwater is rising faster after heavy rain, raising local infrastructure concerns
Summary
A College of Charleston graduate student demonstrated a public dashboard built from 14 city wells showing groundwater rises closely track heavy rainfall and that wetter starting conditions shorten groundwater lag times, findings city staff say could inform where to site buried and above-ground infrastructure.
A graduate student from the College of Charleston on Thursday demonstrated a new public dashboard that displays groundwater elevations from the city's network of monitoring wells and shows groundwater is responding more quickly to heavy rainfall in parts of Charleston.
"For a 1 foot increase in groundwater levels, we're seeing the lag time decreased by about 9.8 hours," said Matthew Swanson, a graduate student who built the code and visualizations for the project. Swanson said his model's explanatory power increased after incorporating lag times across multiple wells and that antecedent groundwater conditions matter in predicting how quickly groundwater will respond to precipitation.
The dashboard currently includes 14 well locations around the city and provides hourly pressure and temperature data, well photos and site coordinates, Swanson said. He said data were available for 11 wells at the time of the demonstration; the White Point Gardens (Johns Island) well and one Rosemont well lacked recent data but are being recovered. The site will be updated seasonally and the team planned a new upload the week after the presentation.
"We started to collect this data, and the first glance at the data, it looked like it does [affect flooding], that the groundwater gets very close to the surface and even comes above the surface, which can cause health issues if we've got standing water," Robert said during the meeting; he framed the monitoring as important to understanding subsidence, heaving and other infrastructure risks.
Swanson described field methods: divers (pressure sensors) suspended on steel cables that corroded in high-salinity sites and were temporarily replaced with fishing line, manual depth measurements using a simple plopper, and scripts he wrote in Python and R to process and correct pressure data into groundwater elevation. He said salinity is increasing at many peninsula and James Island sites and that capillary intrusion and rising saline levels can accelerate degradation of buried infrastructure.
Committee members asked about adding precipitation gauges beyond the airport and whether continuous sensors could track contaminants. Swanson said contaminant testing (nitrate, phosphate, heavy metals) is possible but usually requires denser site networks and targeted sampling because contaminants migrate slowly and testing is costly.
The city said it will host the dashboard on the Office of Resilience and Sustainability website and asked residents and developers to suggest private sites for additional wells if funding becomes available. The committee did not vote on funding or policy changes during the meeting.
Next steps: the College and city staff plan seasonal dashboard updates, recovery of the missing Rosemont/White Point sensors, and discussion of expanding precipitation monitoring to improve model accuracy.
