See inside Duke Energy dam that opened its gates to Mountain Island Lake during Helene
When Duke Energy opened four floodgates at Cowans Ford Dam last fall, it made headlines. On that September day, water surged into Mountain Island Lake, flooding the lake and nearby neighborhoods.
It created more headaches for many people already affected by Hurricane Helene, but officials say few understand how the dam and the Catawaba-Wateree system operates.
This week, Duke Energy invited The Charlotte Observer and other media outlets to tour the hydroelectric system, showcasing enormous energy generating units and the floodgates that protect dam integrity between Mountain Island Lake and Lake Norman.
The Catawaba-Wateree system, which includes 11 lakes, is not designed for flood mitigation but rather energy generation, said Bryan Walsh, a Duke Energy engineer who oversees the system.
The system is responsible for nearly a quarter Duke Energy’s generating capacity in the Carolinas, and Mountain Island Lake and Lake Norman provide drinking water for over 10% of North Carolina residents.
“There’s a lot of work that we have to do to be able to control the water system, control the levels of the lakes and move water so that we are available for drinking water supply,” Walsh said. “We’re available for power generation, we’re available for recreation, and we also are safely maintaining the river system.”
Managing water at Cowans Ford Dam
Cowans Ford Dam stands between Lake Norman and Mountain Island Lake, serving as an energy generating site and a barrier between the two lakes that are dramatically different sizes.
After the remnants of Hurricane Helene hit the Carolinas, Duke Energy drew the ire of Mountain Island Lake residents who say the company could have mitigated the flooding in their neighborhoods.
Duke’s decision not to drastically draw down water levels in Lake Norman and Mountain Island Lake ahead of Helene took into consideration forecasts and drinking water needs, Walsh said. Since September, the utility has maintained it acted appropriately during the storm, and the Federal Energy Regulatory Commission accepted this explanation.
Lake Norman holds about 38% of the water in the Catawba-Wateree system, Walsh said, while Mountain Island Lake holds only 3%. As water makes its way from Lake James, which is west of Morganton, North Carolina, to Lake Wateree in South Carolina, it impacts each lake differently, Walsh said. One foot of water at Lake Norman corresponds to 10 feet at Mountain Island Lake.
If water levels are drawn down and a storm’s path shifts, there could be a serious drinking water shortage, Walsh said. Forecasts are not always perfectly accurate, he said. The only way water is able to reenter the system is through rainfall.
When it comes to public safety, protecting dam safety is a critical element, Walsh said. Duke Energy can’t allow water to flow over floodgates at Cowans Ford because it risks sending trash and debris through the system and could even damage the gates. When water reaches above full-pond level of 100 feet, the gates must open.
“We don’t take the decision to open gates lightly, but it’s a very important decision when you do it, and you got to be perfect when you do it,” Walsh said. “Whether they have to be manually operated or automatically operated, they’re tested, and we also have culpability back to FERC on that.”
Built for energy generation
While some river systems are built specifically for flood control, the primary purpose of the Catawba-Wateree Hydro Project is energy generation.
The Catawba is the first river to be planned and built in the United States specifically for electricity generation, Walsh said. It provides electricity throughout the Carolinas, and cool water for nuclear and fossil generation.
Energy is created as water flows through four enormous turbines. The turbines spin, turning generators and sending energy to transformers. Each of the four turbines is capable of generating 80 megawatts of electricity, said Aaron Dale, director of regulated renewables operations.
At full capacity, the four turbines can move a combined 18 million gallons of water per minute.
How does Duke keep residents informed?
Duke Energy is expanding ways to make sure residents can stay informed about lake levels and current conditions, Walsh said.
The Lake View app, available for Android and Apple users, shows current, maximum and minimum lake levels and is updated continuously. Residents can also call Duke’s lake level phone line at 800-829-5253, or visit duke-energy.com/lakes for information about water levels.
“Having local emergency management officials that know that they can trust our forecast, know that they’ll be able to have a constant line of communication and make calls for public safety is really important,” Walsh said. “We have really tried to do a better job of communicating real time with our customers and residents.”
This story was originally published March 26, 2025 at 12:57 PM.
