IOWA CITY, Iowa — The University of Iowa and cities along the Iowa River prepared for the worst Thursday amid concern that rising waters could top a key reservoir and inundate the area next week.
A projection released Thursday showed that Coralville Lake, a reservoir built to control flooding on the river, would crest next week less than one foot below the emergency spillway. Authorities said they can manage flooding as long as water doesn't top the spillway.
But emergency managers cautioned that rainfall in the Iowa River basin in the coming days could change the forecast for the worst and cause waters to top the spillway, which was breached during the devastating floods of 2008 and 1993. They said no rain was expected until at least Saturday evening, but after that the forecast of possible storms was concerning.
Heavy recent rains in the upper Midwest have caused the Mississippi and many of its tributaries to rise sharply, causing significant flooding in Iowa, Illinois and in Missouri north of the confluence with the Missouri River near St. Louis. The Mississippi remains below flood stage from St. Louis to the south.
A Mississippi River lock and dam was set to be shut, the U.S. Army Corps of Engineers said Thursday as it tries to protect the town of Clarksville, Mo., where the river is already 6 feet above flood stage and rising.
The popular National Tom Sawyer Days festival in Hannibal, will go on as planned over the Fourth of July weekend, though parts of a highway south of town are expected to be closed because of flooding.
The Corps of Engineers has activated its Emergency Operations Center in St. Louis, a move that enables the agency to provide personnel and resources to support flood-fighting efforts.
The federal agency, which manages Coralville Lake in Iowa, said Thursday that it is opening the gates to increase the outflow of water to 18,000 cubic feet per second, near its maximum.
"The lake is doing exactly what it is supposed to do right now: holding those waters back," said Dee Goldman, operations manager at the lake. "But once we get within a foot or so of that spillway crest, then we really start looking at the sky and depending on Mother Nature. It's really in their hands at that point."
The lake, located six miles north of Iowa City, is continuing to rise as it takes in far more water than it lets out as a result of rain that pounded the area in June. The Iowa River upstream from the lake has already reached record levels at Marshalltown and Tama, and those waters are flowing into the reservoir at a rate of more than 30,000 cubic feet per second.
The lake's water levels were at nearly 704 feet as of Thursday morning and expected to crest July 10 or July 11 at 711.3 feet, just below the top of the 712-foot spillway.
Authorities were worried about boating on the lake over the Fourth of July weekend because of debris, and boating has been banned on the Iowa River below the lake.
The university, which is still rebuilding from 2008 flooding that destroyed several key buildings, erected temporary flood barriers to protect a student dormitory and an art building along the river. Spokesman Joe Brennan said the university was closing storm sewers and adding flood protections to utility tunnels, but expected to complete its preparations later Thursday.
Iowa cities along the Mississippi River also are dealing with high water. The river is expected to crest in Davenport early Friday morning and then drop slowly through next week.
The high water has forced the closure of some streets but Davenport officials said the barriers they've set up should protect the city from widespread flooding.
In Burlington, Iowa, officials are expecting the third-highest crest on record and have closed a portion of Main Street downtown to let crews erect flood barriers.