Missouri River floodwaters taking more farmland

An aerial view of a farm near Rock Port, Missouri submerged in Missouri River flood waters June 24, 2011.

KANSAS CITY, Mo (Reuters) - The swollen Missouri River was swamping more farmland in Missouri on Wednesday as federal officials began to prepare for a gradual reduction in water releases from a key dam starting later in July.

Residents from Montana through Missouri have built flood barriers and evacuated homes for more than a thousand miles over the last two months as melting snow and heavy rains overwhelmed six reservoirs on the Upper Missouri River.

Federal officials have released water from the dams at double previous record rates, straining levees through the North and South Dakota capitals down along the borders of Nebraska, Iowa and Kansas and across Missouri.

Some of the latest breaches were in Carroll County, Missouri, about 60 miles east of Kansas City where some barriers have been overtopped by floodwaters, threatening roads and smaller communities.

Earlier on Wednesday, more than 12 square miles of farmland remained under water in Carroll County, due to a primary levee breach along the Missouri River on Monday, said Tyler Beuchwakk, a firefighter in Carrollton, the county seat.

Officials were concerned flooding could widen considerably but it seemed to be under control Wednesday morning and only a handful of homes had been impacted by the flooding, he said.

"We have a handle on it, knock on wood," Beuchwakk said.

U.S. Highway 65 in the area was down to one lane due to high water. Federal officials and the Missouri transportation department had noted the road typically floods for broad stretches when one of the area levees is breached.

The U.S. Army Corps of Engineers has begun to reduce water releases gradually from five of its six dams in Montana through South Dakota. It plans to begin reducing water releases from the sixth dam at Gavins Point on July 30.

Gavins Point is a key dam to focus on for residents living downriver because the Missouri flows freely from there until it reaches the Mississippi River near St. Louis.

The water levels were raised slowly and must be drawn back slowly to allow levees to dry out gradually. The saturated levees could collapse if water levels drop too quickly.

The Corps plans to pull back Gavins Point releases to 155,000 cubic feet per second from the current 160,000 cubic feet per second on July 30 and July 31. It plans to release 150,000 cubic feet per second for the first five days of August.

Those figures are still more than double the previous record release rate from Gavins Point Dam of 70,000 cubic feet per second and the Corps expects releases to remain high for the rest of August.

The Missouri River has subsided enough to allow the Cooper Nuclear Power Station near Brownville, Nebraska, to take itself off the unusual event list.

(Reporting by Kevin Murphy in Kansas City and David Bailey in Minneapolis; Editing by Jerry Norton)