DES MOINES, Iowa – After snows melted last month, the Des Moines Water Works found elevated ammonia levels in both the Raccoon and Des Moines Rivers.
The standard treatment is disinfection with chlorine, but over time the process creates a byproduct called trihalomethane, prolonged exposure to which can cause serious health problems.
In late March, trihalomethane levels were 12.5% above the limit in the Des Moines Public Water Supply, and 15% over the limit in the Southeast Polk Rural Water District.
According to Iowa State University, ammonia in surface waters can come from several sources, including sediment erosion, land-applied manure and animal feedlot runoff. Des Moines Water Works CEO and General Manager Bill Stowe says the source of recent surges in nitrogen byproducts is no mystery.
“The long term trends indicate the nitrogen levels continue to increase on both rivers over time,” says Stowe, “which isn’t terribly surprising if we think about the Green Revolution, the use of agricultural chemicals, [and] higher livestock concentrations in both the Des Moines and Raccoon River valleys. But generally, when the trend is soft, we can adapt to it. Our technologies and our abilities to work with that are ones that are in the business of trying to foresee, and work through. It’s the spikes that really cause us problems.”
The Iowa Nutrient Reduction Strategy is a collaboration between ISU, the Iowa Department of Agriculture and the Iowa Department of Natural Resources to address nutrient runoff in surface waters. While Stowe says he has no objection to the underlying science guiding the strategy, he argues the strategy’s voluntary compliance aspect for non-point polluters, such as farms and feedlots, is absent a timetable or regulatory requirement and greatly complicates the process of keeping drinking water safe downstream.
“The problem that we see is the problem of voluntarism,” Stowe says. “The policy, if you will, coming from the science that essentially says that we want to reduce 45% of the pollutant loads over an indefinite time without any regulatory requirement, that’s a significant issue for us because our responsibility as a business is to provide safe, abundant and clean drinking water each and every day.”
Stowe says a regulatory approach to managing nutrients would address the current issue of pushing the problem downstream, where he says it then becomes the Des Moines Water Works’ problem, but he also believes there’s a middle ground.
“There has to be a reconciliation between ag interests and safe drinking water,” says Stowe. “Other states do a far better job of that than Iowa. We have every interest in working with leaders in the agriculture community to make sure that that reconciliation happens in a way that farm economy can continue to be an important ingredient in Iowa’s economy, but also recognize that the continued degradation of our rivers and streams in Iowa is just unacceptable to us as a community.”