The Army Corps of Engineers has begun the gradual process of reducing flows in the Savanah River about 15 percent, to an average of 3,100 cubic feet per second.

"We started the reductions yesterday because it will take seven to 10 days to gradually move down to the new levels," corps spokesman Billy Birdwell said Tuesday.

The reductions -- bringing the lowest flows since a federal drought management plan was created in 1989 -- are designed to slow the decline of water levels at Thurmond Lake and other upstate reservoirs while balancing those interests with the needs of downstream users, such as drinking water plants in Augusta and North Augusta, large industries and wastewater-treatment facilities.

"It's probably nothing anyone will notice downstream, but it will be noted in the long run upstream," Mr. Birdwell said. "It will buy us extra time should the drought continue as we predict it may."

The lower flows will be in effect through January, rather than through February as originally planned, he said, because of concern over potential impact on the endangered shortnose sturgeon, which lives in the river and spawns in February.

"There is still some discussion about February," he said. "We haven't made a final decision yet."

The flow reduction was applauded by lake-area residents such as Barb Shelley, a facilitator with the Friends of the Savannah River Basin group, which has helped educate residents about the drought and its impact on water management in the upstate reservoirs.

"This is good news and establishes a precedent to going below the current mandated minimum flow of 3,600 cubic feet per second," she said. "However, we are not happy about the reduction only through January, with a possible extension through February, rather than definitely through the end of February."

The city of Augusta, which pulls drinking water from the Augusta Canal and from the river, is not expected to be affected, although there could be environmental consequences for the shoals, which run parallel to the canal.

"We know the city of Augusta will continue to pull what they need through the Augusta Canal, and they've warned us of impacts on the shoals, but we've determined those impacts are not significant enough to avoid this action," Mr. Birdwell said.

Plant Vogtle's twin nuclear reactors 20 miles below Augusta, which consume about 43 million gallons of water daily, will not be affected by the lower flows, said Georgia Power spokeswoman Amoi Jeter .

Farther downstream, the impact on fragile coastal estuaries and the 29,000-acre Savannah National Wildlife Refuge will be monitored. Concerns were raised that lower river flows could let saltwater move farther upstream and affect freshwater areas.

Mr. Birdwell said the corps is prepared to re-evaluate the plan if negative effects are documented downstream.

Currently, Thurmond's pool is 313.99 feet above sea level, more than 16 feet below its full pool of 330 feet above sea level. Forecasts indicate that the lake will continue to drop, despite the movement of more water from Hartwell into Thurmond to enable Thurmond to maintain minimum flows to the river.

Reach Rob Pavey at (706) 868-1222, ext. 119, or rob.pavey@augustachronicle.com.