Hartwell’s releases flow through Lake Russell into Thurmond Lake, which is also releasing larger volumes of water into an already swollen Savannah River.
“We made a controlled release for safety at Hartwell,” corps spokesman Billy Birdwell said.
The dam’s floodgates were opened about 2 a.m. Tuesday and will remain open until water levels recede.
“That area received three-plus inches of rain the other night, and the lake was already well into flood control,” Birdwell said.
The lake’s normal full pool of 660 feet above sea level had risen to 664.88 before the gates were opened. As of 10 a.m. Tuesday, the lake had fallen only slightly – to 664.83 feet above sea level.
Reservoirs upstream from Hartwell also filled rapidly, prompting Duke Power and Georgia Power Co. to release more water from their lakes.
The use of Hartwell’s gates to draw down the reservoir is part of the corps’ mission of flood risk reduction, formerly known as flood control.
“It’s all part of our water control manual, so it’s just what we do,” Birdwell said.
The corps will open floodgates at all three dams later this week as part of a scheduled test of the floodgate components.
During Thurmond Dam’s test, scheduled from 1:30 to 4 p.m. Thursday, spillway gates will be opened from one to two feet to give safety experts the opportunity to evaluate the gates’ readiness. The last such test was more than six years ago.
Though visually dramatic, the tests will have only a minimal impact on reservoir levels.
Although the lakes have been well below full pool in recent years because of long droughts, the corps occasionally has needed to open the gates for emergency water releases.
On Feb. 7, 1998, for example, heavy rains pushed Thurmond Lake up to 335.57 feet above sea level – more than five feet above full pool – prompting an emergency opening of all 23 spillway gates.
The resulting flow downstream surged to 35,000 cubic feet per second, more than eight times the volume released during periods of drought. The use of the gates to release water, however, lowered the pool to below 330 feet above sea level within a week.