Water has started to recede in an Iowa city where flooding submerged hundreds of city blocks and forced 24,000 people to leave their homes.

Overflow from the Cedar River left Cedar Rapids residents scrambling for dry ground when the river crested Friday night.

Officials said Saturday it will be at least four days before workers can begin pumping out water, and told residents it will take time for life to return to normal.

"We're estimating at least a couple of weeks before the flood levels get down right around flood stage and below," said Dustin Hinrichs of the Linn County emergency operations center.

Cedar Rapids -- population 120,000 -- has 438 city blocks under water.

Resident Eva Lacock has lived in the city for 89 years, and said she has never seen flooding on such a massive scale.

"(I'm) stunned. Saddened. Because it's such a beautiful city," she said.

Officials are concerned about the declining supply of clean drinking water. Only one of the city's six wells was working on Saturday, after extensive sandbagging.

"Water is still our primary concern," said Pat Ball, the city's utilities director. "We're still using water at a greater rate than we're producing."

A downtown hospital also had to be evacuated.

"It's a bit overwhelming," said Brian Fagan, the city's mayor pro-tem. "This is an endurance competition. We have to be patient. We have to be co-operative."

The city of Des Moines is also trying to cope with flooding, although it appears to be limited to one neighborhood there. A levee on the Des Moines River ruptured and 270 homes were evacuated.

In Iowa City, Gov. Chet Culver said state residents need to prepare for tough days ahead as the Iowa River rises.

"A real wave of water is on the way as we speak," he said.

Culver has declared 83 of the state's 99 counties to be disaster areas.

"This is our version of Katrina," Johnson County Emergency Management spokesman Mike Sullivan said. "This is the worst flooding we've ever seen -- much worse than 1993," when much of the Midwest was hit by record flooding.

The recent flooding is due to heavy rains that have fallen in the region over the past eight days -- about 20 centimetres. More thunderstorms are in the forecast. The flooding is being blamed for at least two deaths.

With a report from CTV's Tom Walters and files from The Associated Press