SIOUX FALLS, S.D. (AP) - Runoff into the Missouri River basin continues to be extraordinarily low and likely will be only 71 percent of normal for the year, the U.S. Army Corps of Engineers says.

Runoff into Lake Sakakawea was 12 percent of normal in August. Lake Oahe set a record low elevation of 1,570.2 feet above seat level and is expected to be 28 feet below normal elevation at the end of September.

"Reservoir storage fell by 1.5 million acre feet in August," said Larry Cieslik, chief of the corps' water management office in Omaha, Neb.

Because of the low reservoirs, power plants on the river are expected to produce nearly 40 percent less hydropower this year, the corps said. The Western Area Power Administration, which markets the power produced by the dams, had to buy electricity last month to meet its obligations to utilities.

Runoff in August was 46 percent of normal. The amount of water stored in the six reservoirs at the end of August was the lowest on record, the corps said.