Floodwaters in Des Moines on June 14. (Kevin Sanders/Associated Press)

Flood waters are receding in Cedar Rapids, Iowa, and the city is already posting notices about how to deal with the aftermath of the deluge that forced a fifth of the population — 24,000 people — to flee. Officials are concerned about the pressure on the drinking water supply.

The city's temporary website said Saturday that teams of firefighters, utility workers and building inspectors will start Sunday to assess whether flooded homes are safe to enter.

"The city continues to be very dangerous but we are doing everything in our power to get people access to their homes as soon as possible in a safe manner," city council member Jeff Beauregard said.

But flood waters have contaminated three of the city's four wells, meaning a drinking water shortage is looming. Cedar Rapids is encouraging residents to conserve water by cutting back on toilet flushes and showers.

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

More than 400 city blocks and 3,900 homes in the city were flooded when the Cedar River burst its banks. Other streams in Iowa, Minnesota, Wisconsin, Kansas and Michigan also flooded after days of heavy rain across the U.S. Midwest.

Des Moines starting to recover

In the capital, Des Moines, a levee on the Des Moines River broke early Saturday, flooding a neighborhood which has more than 20 homes.

But the city is recovering; its website said downtown bridges were reopening Saturday, and announced arrangements for residents to place flood-damaged items on the curb for pickup.

The voluntary evacuation was also lifted, although a mandatory order was still in place for one area.

Downstream from Cedar Rapids, below the point where the Cedar River feeds into the Iowa River, a flood crest is heading toward Iowa City. But it's not expected to hit until Monday or early Tuesday.

The flooding has caused two deaths in Iowa, and 83 of the state's 99 counties have been declared disaster areas.