A Closer Look: Stream Delivery of Nitrogen and Phosphorus
The Iowa Nutrient Reduction Strategy identified the delivery of nutrients to water bodies by point sources and nonpoint sources. Point sources, like wastewater treatment plants, industry and urban areas, contribute 8% of the nitrogen and 20% of the phosphorus to the stream. The remaining 92% of nitrogen and 80% of phosphorus delivery comes from nonpoint sources like agricultural land. This illustration shows the relative stream delivery of nitrogen and phosphorus from each source, with the arrows sized proportionally.