ST. LOUIS (AP) — Fifteen senators from eight Mississippi River states are urging the Army Corps of Engineers to take steps to keep barges moving on the Mississippi.

Sens. Roy Blunt, a Missouri Republican, and Tom Harkin, an Iowa Democrat, penned the letter to Army Assistant Secretary Jo-Ellen Darcy Friday with 13 co-signers.

It urges the corps to delay plans to reduce the flow from a Missouri River reservoir starting just after Thanksgiving, which would reduce the level of the Mississippi. The letter also asks the corps to undertake work as soon as possible to remove rock pinnacles in the Mississippi River that impede barge traffic in periods of low water.

“The Mississippi River is vital to commerce for agriculture and many other goods, including our ability to export our goods,” the letter stated. “If the river channel is not maintained, there will be a loss of jobs, income to many businesses and farmers, and an adverse impact to the economy of the region as a whole.”

The lengthy drought has parched the nation’s two largest rivers, leaving water levels dangerously low. And long-range forecasts call for the drought to extend into spring.

With that in mind, Major Gen. John Peabody, commander of the Mississippi Valley Division of the corps, announced Friday that he ordered the release of water from an upper Mississippi reservoir. Peabody said at a news conference in St. Louis the release from a reservoir in Minnesota will eventually add 3-6 inches to the river at St. Louis.

“Every inch counts, and we’re trying to squeeze out every inch of capacity that we have,” Peabody said.

But inches fall well short of offsetting the projected drop of up to 3 feet when the corps drastically reduces the flow of the Missouri River at Gavins Point Dam in South Dakota on or around Nov. 23. Plans call for the current amount of release — 36,500 cubic feet per second — to eventually decline to 12,000 cubic feet per second over the course of several days.

Jody Farhat, chief of the Water Management Division for the Northwestern Division of the corps, said Thursday the move is necessary because of drought conditions on the upper Missouri River.

But the decision will have a huge impact on the Mississippi, south of where the two rivers merge. Corps officials have said that if the river drops another 5 feet or so at St. Louis, barge traffic may be halted.

Barges carry 20 percent of the country’s coal and more than 60 percent of its grain exports. Other cargo — such as petroleum products, lumber, sand, industrial chemicals and fertilizer — also gets shipped along the Mississippi River.

Craig Philip, CEO of Ingram Barge Co., of Nashville, Tenn., said a river shutdown would hit consumers directly, creating a “ripple effect of economic loss that would be felt most heavily in the Midwest but would endanger our national prosperity as well.”

Philip said businesses represented by the trade groups American Waterway Operators and the Waterways Council are seeking a presidential declaration that would take two steps to help keep the Mississippi open: Order the corps to maintain the existing flow on the Missouri; and expedite efforts to remove rock formations on the Mississippi River bottom at two locations in southern Illinois.

Current plans call for the rocks to be removed in February. Philip said they need to be taken out much sooner to keep the channel clear for barge traffic.

“This is not mere rhetoric,” Philip said. “The situation is urgent. The consequences could be dire.”

In addition to Blunt and Harkin, senators who signed the letter on Friday included Claire McCaskill of Missouri, Chuck Grassley of Iowa, David Vitter and Mary Landrieu of Louisiana, Richard Durbin and Mark Kirk of Illinois, Lamar Alexander of Tennessee, Thad Cochran and Roger Wicker of Mississippi, Amy Klobuchar and Al Franken of Minnesota, and Mark Pryor and John Boozman of Arkansas.

Missouri Gov. Jay Nixon and Illinois Gov. Pat Quinn have also urged the corps to reconsider the reduced flow on the Missouri. But corps officials in Omaha, Neb., say they are bound by the Missouri River Master Manual to act in the best interest of the Missouri River basin.

Corps officials in St. Louis say they’ve taken extraordinary measures to keep the Mississippi open for as long as possible.

“It’s a critical reality that we need more rain,” Peabody said.