Within 10 days, drought-parched Thurmond Lake is expected to fall to its lowest level since 2002, triggering Level 3 of the Corps of Engineers' drought-management plan for only the second time since it was adopted in 1989.

Under the plan's strategy additional water would be moved from Lake Hartwell to keep Thurmond full enough to maintain the minimum flows into the Savannah River needed by downstream users.

"It may not happen in the next seven days, but probably within a week-and-a-half," said Stan Simpson, the corps' Savannah District water control manager.

The reservoir's pool level, and the drought plan's Level 3 benchmark, are important because they dictate how much water is released into the Savannah River for drinking, industrial processes and wastewater dilution for Augusta, Columbia County, North Augusta and a number of industries.

Although the corps is obligated to maintain a minimum flow of 3,600 cubic feet per second into the Savannah River, that would require the release of more water from Lake Hartwell.

Thurmond Lake's pool is 316.56 feet above sea level, or 13.44 feet below the full pool of 330. Once it falls to 316 feet, the corps implements Level 3 of its drought management plan, which calls for increased public warnings about low water hazards and restricts releases to the river to 3,600 cubic feet per second.

On this date a year ago, the lake was more than six feet higher than it is this year. The low point in 2007 occurred on Christmas Day, when the lake fell to 316.18 feet.

Because the lake has been low much of the year, the corps is voluntarily releasing less water to slow the reservoir's decline, Mr. Simpson said.

The lake last fell below the 316 mark on Sept. 6, 2002, he said.

"We had barely fallen below it, and it only lasts about a week," he said. "It was just when the previous drought had started to recover. It got as low as 315.3."

Before 2002, the lake hadn't fallen below 316 feet since Feb. 21, 1989, when the pool level dwindled to 312.91 feet above sea level.

Mr. Simpson said it will probably not fall as low this time because the drought plan requires that the levels of Thurmond and Lake Hartwell upstream be balanced on the basis of its remaining storage pool.

That means more water will be released from Hartwell to keep Thurmond from falling below the point where it can no longer maintain its minimum flows into the Savannah River.

Because of that policy, Hartwell could fall as much as five feet for every three-fourths of a foot that Thurmond declines, he said.

"Right now there is very little rain in sight and if we don't get a change in the weather it is going to be setting new records later this year," Mr. Simpson said.

Fifteen of the corps' 33 public boat launch sites are closed.

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