Waubay Lake Flood Study Identifies Risks to Highway 12, Day County Homes
Northeast Radio SD News – Day County, SD - Engineers with the U.S. Army Corps of Engineers Omaha District joined Northeast Radio SD host Steve Jurrens on Friday, Oct. 30, 2026, to outline the findings of a recently completed technical flood risk study examining rising water levels at Waubay Lake in Day County.
Unlike the ongoing flood control feasibility study in Watertown and Codington County, the Day County initiative was conducted as a Section 22 technical support effort funded 100 percent by the federal government. The report, completed in September, provides local leaders with hydrological data, long-term elevation projections, and conceptual drainage alternatives rather than immediate construction plans.
Closed Basin Challenges and Rising Water Levels
Waubay Lake operates as a closed basin lake with no natural outflow until water reaches an elevation of approximately 1,811 to 1,812 feet. Because evaporation is currently the only natural way water leaves the basin, runoff from major rain events continues to raise the lake’s elevation over time.
"It doesn't have a natural outflow until elevation about 1,811, 1,812 is where the natural outflow would be, which is long feet away," said Tony Krause, a civil and hydraulic engineer and 20-year water resources specialist with the Corps of Engineers Omaha District. "And so every time it rains, the water, gravity pulls it down into the lake. And other than evaporation, there isn't a way for it to get out. So every time it rains, it'll continue to rise and continue to rise."
Infrastructure Risks Along U.S. Highway 12
Project manager Kristle Beaudet, a civil and geotechnical engineer with the Corps' Omaha District specializing in dam safety and flood risk management, said the September report identifies critical infrastructure and property around the lake that could be inundated if water levels keep rising.
Key areas evaluated in the study include:
· U.S. Highway 12: Potential flood impacts along the corridor cutting across between Webster and Waubay.
· Railroad Infrastructure: Risks to rail lines operating near the lake basin.
· County Roads and Commutes: Potential road closures that would force detours and increase travel times for area residents and agricultural producers.
· Shoreline Structures: Homes and private properties situated along the lake.
"Dealing with a closed basin, there aren't that many in the U.S., so this is a complex problem and the community needed the technical expertise of the Army Corps to assist them," Beaudet said. "Using those capabilities, we can help better define the problem that the community is facing with their flood situation, potential flooding in the future. And so identifying the problem and identifying those risks are very crucial before you can start forming a solution."
Conceptual Mitigation Options and Downstream Protections
At a screening level, the Corps evaluated conceptual ways to manage or arrest the lake's rise, including pumping water out of the basin or building a constructed outlet structure. Engineers also examined how much water would need to be diverted and what times of year releases could occur without creating downstream flooding for other communities.
Beaudet emphasized that the September report provides conceptual paths only and does not authorize or fund any construction. Moving toward a constructed project would require a formal feasibility phase, compliance with the National Environmental Policy Act, and extensive coordination with downstream and state partners. While the technical study was 100 percent federally funded, large-scale Corps flood risk construction projects typically operate on a 65 percent federal cost share.
Day County Forms Water Mitigation Team
After the Corps presented preliminary findings during the study, Day County leaders established a local water mitigation team to address the long-term threat and began reaching out to state officials for support.
Because Army Corps authorities are community-led, any future phase—whether emergency planning support or a formal construction feasibility study—depends on how local leadership chooses to proceed. In the meantime, Krause encouraged Day County homeowners to stay informed about flood insurance, family preparedness plans, and property-level risk management.
"While that isn't something that you're facing tomorrow, it's something your community and your family and your home will probably have to manage at some point," Krause said. "So getting risk aware and starting to understand what you can do at a homeowner level is probably one of the biggest things I would put out there for your listeners."
