By Michael Avok
HAMBURG, Iowa (Reuters) - Federal officials increased water releases from two South Dakota dams on Saturday to make room for expected potentially heavy rains through early next week, adding to flooding woes along the Missouri River.
The U.S. Army Corps of Engineers water releases from five dams in North Dakota and South Dakota had already about doubled prior records to relieve reservoirs swollen by heavy winter snows and spring rainfall at the river's Montana headwaters.
With severe storms expected through Tuesday that could dump inches of rain in some areas, the Corps plans to increase flows by nearly 7 percent at the Oahe Dam above Pierre, South Dakota's capital, and the Big Bend Dam just downstream.
"We do have the potential for a strong storm system," Andy Church, a National Weather Service meteorologist in Aberdeen, South Dakota, said on Saturday.
Some 2 to 3 inches of rain could hit areas of North Central and Eastern South Dakota, with flooding possible on the outside of levees in Pierre, Church added.
The increased releases had South Dakota officials concerned about the strain on levees in Pierre and Fort Pierre nearby.
"The state is working with the Corps to ascertain the impact this will have, so that we can ensure the levees remain effective," South Dakota Governor Dennis Daugaard said.
"I am also very concerned about the effect this will have on private levees that were built relying on Corps information."
The Corps plans to release 155,000 cubic feet per second from the Oahe and Big Bend dams on Saturday and 160,000 on Sunday, up from the roughly 150,000 it has been releasing.
It said the reservoir above Fort Randall Dam had capacity to handle the added flows and the temporary levees in Pierre and Fort Pierre could handle the heavier releases. It also has no immediate plans to increase releases from Gavins Point Dam.
Gavins Point is closely watched because the river flows freely from there for more than 800 miles straddling Iowa and Nebraska and through Missouri to the Mississippi River.
Downstream from Gavins Point in affluent Dakota Dunes, contractors stockpiled materials to be ready if temporary levees there sustain another partial collapse. On Thursday, a partial collapse was discovered and repaired in Dakota Dunes.
The swollen Missouri River has flooded areas from Montana through Missouri, forcing residents to shore up protections and raise temporary levees around towns. Thousands of people have evacuated homes along the river, and more may need to go.
A levee breached at Hamburg, Iowa, on Monday where about one-quarter of the town's 1,200 residents were under mandatory evacuation. A secondary levee was raised to protect the city.
The hectic scramble to protect Hamburg gave way to quiet confidence on Saturday. Where dozens of people feverishly moved dirt and sand for two weeks to build the levee, now only a couple workers remained to monitor it.
"They built that levee out of the right thing, the right materials," said Chuck Behr, Hamburg Bakery owner and a former city councilman. "There's no reason to think we are in jeopardy."
Most customers who popped in and out of Behr's bakery Saturday morning said they expected the levee to hold.
Floodwater continued to spread over Hamburg-area farmland. Interstate 29 was still closed in the area, and on one alternate route, Nebraska Highway 2, westbound motorists drove through about 3 inches of moving water in spots.
With peak releases planned until at least mid August and high flows expected until December, officials urged residents on Saturday not to let their guard down.
Mandan Mayor Tim Helbling told reporters he saw residents mowing their lawns and using weed-eater machines on their sandbags and dikes in a drive around Saturday.
"That is probably not a good idea folks ... because they will do a lot of damage," Helbling said Saturday.
"I know your yard needs to look pretty, but I think there are other priorities that should be in line first."
(Additional reporting by David Hendee in Omaha and David Bailey in Minneapolis; Editing by Jerry Norton)