IOWA CITY, JULY 11 -- Central Iowa, far upriver from the flooding Mississippi, was overwhelmed by the flooding Des Moines and Raccoon rivers today, which swamped downtown Des Moines and a water treatment plant, leaving 250,000 people without drinking water.

The National Guard was called in to deliver potable water, beginning with hospitals, nursing homes and flooded residential areas where people cannot leave their homes. But all major roads into Des Moines were closed, complicating the task.

Even as the National Weather Service predicted a break within two days in the pattern of drenching storms, cities downstream and along other tributaries in the soaked state were warned to expect more flooding as rivers continue to rise.

"The magnitude of this flood is far beyond anything we've experienced in the history of the state," said Gov. Terry E. Branstad (R).

More than 30,000 people have been forced from their homes along the Mississippi and its many tributaries, the Associated Press reported.

Levees continued to wash away as rising waters flowed toward the confluence of the Mississippi and Ohio rivers at Cairo, Ill., where officials said the flooding should largely end, partly because the river is able to handle more water at that point and because the Ohio's water flow is normal.

A levee failed on the Mississippi south of Burlington, Iowa, this morning, flooding about 17,000 acres, AP said. In Missouri, just north of St. Louis, water from the Mississippi broke through a levee near Portage des Sioux during the night and flowed across a largely agricultural peninsula up to a levee along the Missouri River, about 20 miles from the point where the rivers usually meet.

There were indications the Mississippi might cut a new channel to the Missouri across the bottom land where the two meet just north of St. Louis.

National Weather Service Director Elbert W. Friday Jr., speaking on CBS's "Face the Nation," said weather patterns finally appear to be returning to normal, promising some relief in about two days. But he said so much rain has fallen that some flooding could last through August.

"The good news is that the weather pattern seems to be returning more to the normal, which means that we expect a lessening of the rains in the upper Midwest," he said. "We expect the rains to last for the next two days fairly heavily, as they had done in the last couple of weeks, and then recede."

That cannot come soon enough for thousands of people who have lost homes and livelihoods.

"This is heart-wrenching. This is worse than death," said Joseph Markovich, 78, who was evacuated with his wife Ethel, 72, early Friday morning, 35 years from the day that they moved into a house in Lemay, Mo., just south of St. Louis.

"It's sad because I have so many memories of my children in there," said Ethel Markovich. "How many times can you come back and rebuild the same thing?"

Ilene Carr, 65, whose first house was destroyed in a 1973 flood, also was evacuated Friday morning just after returning from her job at a concession stand in Busch Stadium.

"In '73 I had relatives, but they're all deceased now. I've got nowhere to go," she said. "I don't like to talk about it. I cry every time I talk about it."

Iowa has emerged as one of the flood's worst spots, partly because much of the rain that has fed the flood in recent days fell in Iowa or in the watersheds to the west.

In Des Moines, workers toiled through Saturday night and early this morning to save the municipal water plant, but the effort proved futile even though it is seven feet higher than nearby levees.

When a levee broke, the flood gushed in, swamping the water plant.

"It went over that thing {the levee} like it wasn't there," said resident Don Boyven.

"It looked like a wall of water," said amateur radio operator Leroy Coder, who watched the river breach a levee on the northern edge of the city's business district. "There's about six feet of water there now."

The city has declared a water emergency, warning that all water should be considered contaminated. The National Guard and city officials began setting up 125 distribution sites to provide potable water, trucked in from as far away as Omaha.

Officials said it will take at least seven to 10 days to restore water service. Meanwhile, drinking water will not be the only problem. Electricity is out in parts of the city, including the downtown area, and officials encouraged downtown businesses to suspend operations for at least 48 hours. Branstad said that sprinkler systems are inoperative, creating a fire hazard in commercial buildings.

The Des Moines Register was flooded out, but assistant city editor Marvin Hastings said a temporary newsroom would be set up in a hotel to put out an eight-page flood edition that the Indianola Record-Herald, 15 miles away, would lay out and the Iowa City Press Citizen would print.

Officials of the U.S. Army Corps of Engineers, which controls the Saylorville Reservoir dam on the Des Moines River above the city, said they will try to reduce temporarily the outflow from the dam, but so much water is entering the reservoir that the flow cannot be held back for long.

When one dam releases water, it creates a domino effect downstream.

Gerald Dowell, manager of the Red Rock Reservoir between Des Moines and Ottumwa, said he is increasing his flow from the already huge 92,000 cubic feet per second to a record 100,000 cubic feet per second.

"When we get anything over 40,000, it starts to damage things downstream, so there's literally tens of thousands of acres flooded downstream," Dowell said.

Staff writer Michael S. Arnold in St. Louis contributed to this report.