(Updates with eighth lock likely to close, Gulf grain export prices rising)
By Karl Plume
April 18 (Reuters) - Eight Mississippi River locks between Muscatine, Iowa, and Clarksville, Missouri, were expected to close beginning on Friday as the rain-swollen waterway rises above flood stage, the U.S. Army Corps of Engineers said on Thursday.
Corn and soybean prices at Gulf of Mexico export terminals jumped by at least 10 cents a bushel as the closures of Locks 16 through 24 will shut the river to commercial navigation from central Iowa to northern Missouri, dramatically cutting available supplies for exporters.
The flooding is a dramatic departure from just three months ago, when the river dropped to near record lows and nearly closed to commercial navigation entirely.
The river was forecast to crest on Monday at Lock 16 in Muscatine at a river gauge reading of 21.9 feet, nearly 6 feet above flood stage and 3.7 feet below the record crest, according to the latest National Weather Service (NWS) river forecast.
"Based on current forecasts, we're looking at most of them closing on Friday," said Rob Germann, operations manager for the Army Corps' Mississippi River project, Rock Island district, which operates Locks 11 through 22.
"Depending on how the rain continues this week, will determine how that crest drains out," he said.
At Lock and Dam 24 in Clarksville, the river was forecast to crest at 35.6 feet on Sunday, more than 10 feet above flood stage and 2.1 feet short of its record crest at that location.
That lock will be closed after the river rises to 32.5 feet, said Army Corps' St. Louis District spokesman Michael Petersen, a mark that may be topped late Friday, according to the NWS.
About 60 percent of U.S. grain exports are shipped via the Mississippi River and its tributaries from farms in the Midwest to export terminals at the Gulf of Mexico. The closures, which could stretch into next week, reduce the area from which exporters can draw barge-delivered grain to just the Illinois River, lower Ohio River and the Mississippi from St. Louis and south. (Reporting by Karl Plume in Chicago; Editing by Gerald E. McCormick, Bob Burgdorfer and Dan Grebler)