Bacteria, chemicals, and debris in the flood water have county and health officials concerned. People in areas where flooding could occur need to take steps to protect their drinking water sources.
Emergency management officials say the flood water coming down the Platte River is slowing, but Buffalo and Hall Counties are still preparing for it to spill over the banks.
"Those properties that are lowest along the river - the pasture-lands, the roads, the low-lying access roads that seem to get water in these instances are going to get water again," says Jon Rosenlund, Grand Island/Hall County Emergency Management Director.
The water that's coming is not clean, and officials say residents who live by the river need to make sure any water sources like private wells have their vents capped and waterproofed as much as possible. If they are underwater, officials say power to them should be shut off.
"The concern with floodwater is contamination that's come downstream, either from septic tanks or from dead animals in that water, things like that," says Andrew Hills, Emergency Response Coordinator for the Central District Health Department.
Agencies like CDHD and the Red Cross have free water testing kits that take a sample from the faucet. CDHD's water lab can have results in about a day.
"If you have a well within the flood area, or where it's next to and could have seeped into it, or you're just concerned, and in any case every 12 months, you should get your water tested," says Hills.
Besides drinking water, officials say Nebraskans need to avoid boating in the river, and to also avoid canals and lakes that are taking on floodwater too.
The City of Kearney wants canoes and kayaks to stay out of the canals there until further notice.
"Not only is it unsafe to be on the water, on the river, on the canals because of the high flows and the flood stage and the debris that's going to be in it, but we know that some of the water has been contaminated and it just won't be safe for people," says Kearney/Buffalo County Emergency Management Director Darrin Lewis.
With more water still coming behind this initial surge, officials think the river could maintain high flows well into October.