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 or THM, prolonged exposure to which can cause serious health problems.
In late March, THM levels were 12.5 percent above the limit in the Des Moines Public Water Supply and 15 percent 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. CEO and General Manager of the Des Moines Water Works Bill Stowe says the source of this year's surge in ammonia levels and last year's spike in nitrate levels are no mystery.
"The long term trends indicate the nitrogen levels continue to increase on both rivers over time, which isn't terribly surprising if we think about the green revolution, the use of agricultural chemicals, 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.
Stowe says there's no argument against the science behind the strategy, but how that is put into action is a different story.
"The problem that we see is the problem of volunteerism. The policy if you will, coming from the science that essentially says that we want to reduce 45 percent 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 it becomes the Des Moines Water Works' problem.