Carolyn Voter wants to create a better picture of how water moves through the world around us.
Voter, who joined the University of Wisconsin-Madison Department of Civil and Environmental Engineering in fall 2026 as an assistant professor, is a water resources engineer who studies how water interacts with built and natural environments.
That focus surfaces in Voter’s ground- and stormwater research. They can be closely connected: How a city manages stormwater can influence how rapidly water infiltrates local groundwater tables, with meaningful consequences.
For example, while several factors have contributed to recent flooding in Milwaukee, Wisconsin, one important aspect is that heavy rains can overwhelm the city’s combined sewer system. Voter says combined sewer systems, which are common in older cities like Milwaukee and along the East Coast, merge stormwater and wastewater systems into one.
When it rains, all of that water flows into the system’s wastewater treatment facilities. Heavy rainfall can force the system to discharge untreated water. This has led to situations where the city of Milwaukee advised residents to reduce water usage to relieve strain on the system.
A similar issue runs in the opposite direction: groundwater intrusion into the sewer system.
“Any sanitary sewer – combined or separate – is leaky at the best of times,” Voter says. “If the groundwater rises such that the pipes are submerged, you can get infiltration into the pipes, and that has a similar fate as stormwater in combined sewer systems, which gets conveyed into the wastewater treatment plant and has to get treated. Depending on how bad the leaks are, that can sometimes be a substantial portion of flow going into the wastewater treatment system.”
Voter has been researching how to identify or predict which locations in a sewer system are most likely to experience groundwater infiltration so operators can better manage the problem.
Because this occurs underground, it’s difficult to see the process as it happens. There are powerful modeling tools for both stormwater and groundwater. Voter says the U.S. Geological Survey’s MODFLOW excels at groundwater modeling, and the U.S. Environmental Protection Agency’s Storm Water Management Model excels at pipe flow. But there isn’t a tool that combines those capabilities in the way they’re needed to model groundwater intrusion into sewer systems.
So she’s creating it.
“One of my group’s current projects is coupling the gold standards in these areas so that we can get a better look at these interactions and understand where, how and under what conditions they happen,” Voter says.
The problem is a growing concern anywhere with rising groundwater levels, she says. Coastal communities face an added complication: Sea level rise can push saltwater into the groundwater, which can further strain or damage underground infrastructure.
Voter also researches groundwater cycles over long periods and how groundwater withdrawals affect surface water ecosystems, particularly in streams and lakes. And she studies green infrastructure, such as bioswales or rain gardens, and how communities can use them to meet both hydrological and social goals for stormwater management. Bioswales use vegetation to control stormwater runoff. In urban environments, they can provide benefits beyond stormwater management, and Voter says that can influence where planners place them.
She’s also studying how they can serve as long-term infrastructure pieces.
“These have only really become popular in the last 10 to 20 years, so they’re fairly new as a strategy,” Voter says. “Because they’re so new, we don’t have a lot of great information on how they evolve over time, but they must be evolving because they are living systems. Some of our recent work has been looking at some of the oldest installations to understand what makes them successful or not over the long term, when it comes to meeting hydrological, ecological, social and community goals.”
Voter worked as assistant professor at the University of Delaware from 2022-26, but her research as a faculty member builds on work she began as a civil and environmental engineering PhD student at UW-Madison. With her advisor, Civil and Environmental Engineering Professor Steven Loheide, and Daniel Wright, the Arno Lenz Memorial Associate Professor of Water Resources Engineering, Voter studied how to optimize the implementation of green infrastructure and how it can mitigate runoff from extreme rainfall events.
Next, she was a postdoctoral researcher through the Aquatic Sciences Center at UW-Madison. She also worked with the Wisconsin Department of Natural Resources through a Wisconsin Water Resources-Science Policy Fellowship to study how groundwater withdrawals affected lake levels in Wisconsin’s Central Sands region.
“All told, I think I was here for nine years, and my work at the time really set the stage for what I am doing now,” Voter says. “I loved my time here. It’s a fantastic place to study water. We’re on the Great Lakes and bordered by the Mississippi River, and have so many wonderful lakes and rivers across the state. I heard people say it when I was a postdoc, but I really appreciate it now: Wisconsin is unique in how well people connect and collaborate around water issues. I’m so excited to return to this community, and to get to work on some of these important water challenges in the state and beyond.”
Photo of Carolyn Voter by Joel Hallberg