The lowest average flows in the Savannah River might get even lower.
Tests could begin this winter to gauge the environmental impact of dipping below the 3,600-cubic-feet-per-second flow that is considered the minimum needed to protect water quality.
"It's being looked at," said Army Corps of Engineers hydrologist Stan Simpson, who briefed a Joint Savannah River Committee on drought issues Thursday.
On an annual average, 9,000 cubic feet of water per second flow from Thurmond Lake into the river that supplies Augusta and North Augusta with drinking water, wastewater dilution and industrial process water.
During drought, flows can be reduced to 3,600 feet per second -- a low flow that has been part of the corps' drought plan since the 1980s.
Though that minimum provides adequate water downstream, it can also cause Thurmond Lake to empty faster during droughts, when inflows to the reservoir are less than minimum outflows.
In 2003, hoping to slow the lake's decline, the corps proposed reducing minimum flows to 3,000 cubic feet per second but dropped the idea after objections were raised over the plan's effect on fragile estuaries at the mouth of the Savannah.
Georgia's Environmental Protection Division and the South Carolina Department of Health and Environmental Control are now interested in modeling the effect of lower flows.
"We told them, 'Tell us what you want and we'll model it,' " Mr. Simpson said, noting that both state agencies use the minimum flow as a basis to issue permits that govern water withdrawals and sewage outflows.
The tests would be conducted between November and February and could include reducing minimum flows in 500-cubic-feet-per-second increments.
Recurring drought and increasing development have strained the Savannah River's water supplies, which are also vital for hydropower and recreation on lakes Thurmond, Russell and Hartwell.
This year, inflows to the reservoirs are already tapering off, even though the minimum outflows of 3,600 feet per second must be adhered to, Mr. Simpson said.
Adequate inflows were recorded earlier in the year, but in May they fell to 2,600 feet per second.
Last year, inflows reached as low as 300 to 400 cubic feet per second some months, while releases into the river remained at 3,600. On Christmas Day, Thurmond Lake fell to the year's lowest level: 316.18 feet above sea level, or 13.82 feet below full pool. On Thursday, the lake was at 320.88.
The Joint Savannah River Committee, which met Thursday in Aiken, was formed by South Carolina Gov. Mark Sanford and Georgia Gov. Sonny Perdue to allow officials to meet periodically to explore water use issues involving the Savannah River, which is shared by both states.
Reach Rob Pavey at (706) 868-1222, ext. 119, or firstname.lastname@example.org.
A flow of 3,600 cubic feet per second in the Savannah River is considered the minimum needed to provide adequate drinking water and sewage dilution. This year's Thurmond Lake inflows (in cubic feet per second):