Florence's Rains Are Kicking Hydroelectric Dams Into Overdrive

(Bloomberg) -- Florence’s driving rains are forcing hydroelectric dam operators to run generators at full tilt and open flood gates that haven’t been used in more than 20 years.

The Tennessee Valley Authority -- which operates dams in Tennessee, Georgia and other states -- began increasing output last week to make room in reservoirs. Duke Energy Corp. has been doing the same in North and South Carolina.

Florence's Rains Are Kicking Hydroelectric Dams Into Overdrive

TVA, a corporate agency of the federal government, went beyond cranking up generators and opened spill gates at the Cherokee Dam on the Holston River near Knoxville, Tennessee, that haven’t been used for flood control since 1994, spokesman Travis Brickey said.

“We went to full turbine capacity at most facilities early last week,” Brickey said in an interview. “As the week progressed, we started more aggressive releases.”

Florence's Rains Are Kicking Hydroelectric Dams Into Overdrive

Rain in North Carolina and southwest Virginia feeds the Tennessee River watershed where reservoirs were already at seasonal high levels before the storm. While forecasts called for around 15 inches (38 centimeters) from Florence in some parts of North Carolina, only about 6 inches have actually fallen, Brickey said.

Florence, which made landfall Friday as a Category 1 hurricane, continues to drench the mid-Atlantic. Flood warnings are in place from North Carolina to Virginia, according to the U.S. Weather Prediction Center in College Park, Maryland.

Rivers in North Carolina are still rising. The Cape Fear River in Fayetteville was almost 17 feet above flood stage Monday and forecast to rise another 10 feet by Tuesday. Flash flood watches have been posted from West Virginia to New England.

TVA plans to stop spilling water at hydro dams Monday. Duke said it will assess flood damage at hydro dams after the storm passes.

“We are still operating all our available hydro generating units to move water through our river systems,” Kim Crawford, a Duke spokeswoman, said in an email. “This includes gate operations on some dams as well as running the generating units to increase storage capacity in our largest reservoirs.”

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