Runoff from recent heavy rains is expected to push Thurmond Lake this weekend to its highest level in a decade, according to the Army Corps of Engineers.

The 70,000-acre lake began filling rapidly after 3 to 4 inches of rain fell across much of the basin, corps spokesman Billy Birdwell said. Some areas recorded as much as 6 inches of rain.

The lake's full pool is 330 feet above sea level. By late Thursday afternoon, it was at 331.5 feet and is expected to crest above 334 feet by late Saturday.

"Right now the inflows into the lake are just tremendous," Mr. Birdwell said.

"Yesterday the local inflows from all the tributaries were about 65,000 cubic feet per second."

Similarly heavy inflows to the Savannah River below Thurmond Dam are keeping the river higher than usual, he said, and the corps is releasing only about 1,000 cubic feet per second from the lake into the river.

"By holding that water back, we are helping to prevent localized flooding farther down the river," he said. "As soon as the downstream flows start to subside, we'll be raising our discharges so that downstream flows will remain at about 20,000 cubic feet per second."

The last time the lake's pool exceeded 334 was on Feb. 2, 1998, when it crested at 334.36, according to corps records. The lake reached 333 several times in fall of 2004.

Although a full reservoir is welcome news for lake-area residents who have been plagued by drought and low water levels in recent years, the rising waters also present some challenges.

"People who have docks may want to come up here and check on them," said Nelson Brooks, a lakefront homeowner in Lincoln County. "When the lake comes way up, the dock cables get a lot of slack in them, and if it's windy, it can damage the catwalks."

Mr. Birdwell said both the lake and river will likely remain higher than usual for about two weeks.