Due to high nitrate levels in the Des Moines River, the Ottumwa Water Works issued a water conservation advisory for Ottumwa that went into effect Tuesday.
Water Works tests nitrate levels every day to make sure they stay below the maximum of 10 parts per million that is established by the Environmental Protection Agency. The river has been over that maximum since May 13 and since then, river water has been blended with alternate sources from Black Lake and the Ottumwa reservoir to bring the levels down.
Right now, there is a 65-day supply in the reserve water, so a water conservation by residents and the city will extend that supply.
"With nitrates running at a higher level, we have to blend our river water with our other source water and those sources are starting to dwindle on us," said Mike Heffernan, Manager of Ottumwa Water Works. "We're hoping people to conserve to extend our supply water so we can keep blending with the river water for hopefully several more months."
Nitrates get into drinking water as a runoff from fertilizers from corn crops, animal waste and pesticides. Nitrate levels are not so high that there is a risk to drink it, but Heffernan said boiling water, which many people do, is actually one of the worst things you can do. Nitrates are not bacteria or an organism, and thus will not evaporate by boiling.
Water Works is working with the Army Corps of Engineers to reduce the flow at Red Rock, which will slow the flow of water in the river. This allows the sun to penetrate the river's surface and grow algae, which soaks in and consumes nitrates. Hot, dry weather helps with this as well.
If those efforts do not reduce the nitrate level, the next step is to issue a bottle water advisory.
The latest Ottumwa Water Works has had to deal with high nitrate levels is the first week of August, so Heffernan said the facility will continue to monitor the river and hope the levels will get back to manageable within a couple of weeks.