AUDIE CORNISH, HOST:
Historic flooding along the Missouri River is starting to recede. Even so, many cities that rely on the river for drinking water have issued warnings. Andrea Tudhope of member station KCUR in Kansas City reports.
ANDREA TUDHOPE, BYLINE: Over the weekend, Five Mile Creek backed up, causing a wastewater treatment plant in Leavenworth, Kan., to overflow. On Saturday, that plant was spewing partially treated sewage into the floodwaters. Lifelong Leavenworth resident Jim Baskas said he'd seen several floods but nothing like this.
JIM BASKAS: Back in 1953 was worse than this. I was a little guy, but I remember that one. In '93, it was bad. But this here - the sewage treatment here - that - boy, that's something else.
TUDHOPE: The flooding broke records all along the Missouri River, like in St. Joseph, Mo., where the river crested at a record high of just over 32 feet. But Jeffery Robichaud, water director for the EPA in Lenexa, Kan., says that doesn't mean it has caused record contamination.
JEFFERY ROBICHAUD: Traditionally what we see is increases in sediment and silt.
TUDHOPE: Robichaud says those aren't contaminants that pose a threat, but they do increase the turbidity of the water - that means the murkiness of the water - making it more difficult to detect contaminants. He says the biggest threats come when flooding reaches industrial areas or sewage plants like the one in Leavenworth. But as floodwaters recede, contaminants dilute.
ROBICHAUD: It's a complicated system. And it's not just the Missouri, but it's also the Mississippi and the Ohio Rivers, which contributes to the water quality that we see in the Lower Mississippi and in the Gulf itself later in the year.
TUDHOPE: Meanwhile, water quality warnings have been issued across the region, including in Kansas City where parts of the river didn't significantly flood.
(SOUNDBITE OF WATER SLOSHING)
TUDHOPE: Here at the water treatment plant in Kansas City, I'm standing over the basin where lime is added to the water to improve taste and odor. The water looks brown and foamy. Water quality educator Lara Isch says that's from sand and silt particles, which increase a lot when there's a flood.
LARA ISCH: We're trying to get all those particles to, like, condense and then fall out of the water.
TUDHOPE: Over the weekend, water officials warned that they had failed to meet treatment standards for the removal of cryptosporidium, which is essentially a parasite.
BROOKE GIVENS: That doesn't mean that there's cryptosporidium in the system. It means that there's an increased risk it could happen.
TUDHOPE: That's KC Water's spokeswoman Brooke Givens. Utility is cautioning some seniors and others to avoid drinking tap water for the next few days. For NPR News, I'm Andrea Tudhope in Kansas City. Transcript provided by NPR, Copyright NPR.