Thurmond Lake has fallen almost a foot since Thursday, but it could be several weeks before the Savannah River returns to normal flows near Augusta.
Thurmond, the farthest downstream of the three reservoirs, is being drawn down first to free up space to store floodwaters now detained upstream in lakes Russell and Hartwell, said Billy Birdwell, a spokesman for the Army Corps of Engineers.
“We try to draw the lakes down in the order of downstream to upstream to reduce the risk of flooding,” he said. “We do Thurmond first, and that way we have a place for the water in Russell and Hartwell to go.”
The network of dams and lakes is designed to store floodwaters that can be moved gradually from lake to lake, and eventually into the lower river, to prevent the catastrophic floods that once plagued Augusta.
Thurmond’s pool Monday was 331.3 feet above sea level, almost a foot lower than the 332.25 recorded Thursday. Normal full pool is 330.
River flows near Augusta also tapered off somewhat over the weekend, mainly because of reduced inflows from Stevens Creek and other entry points below Thurmond Dam.
According to the U.S. Geologic Survey, the river’s flow at Augusta was 48,000 cubic feet per second on Saturday. Monday’s velocity was about 41,000 cubic feet per second.
The river’s pool elevation at Augusta had dropped slightly by Monday afternoon after peaking at 117.5 feet above sea level – the National Weather Service benchmark for flood stage – on Saturday.
Monday’s pool was at 117 feet above sea level.
Birdwell said water from the upper two lakes will be moved downstream as soon as there is room to do so.
Russell’s pool Monday was 479 feet above sea level, or four feet above full pool. Lake Hartwell’s elevation Monday was 664.6, or 4.6 feet into its flood storage zone.
“Once we get Thurmond down to 330, then we start moving water down from Russell, so it will continue to go downstream at the same rate, and then we do the same thing at Hartwell,” Birdwell said. “So you can expect the river to be high for several weeks, at least.”