The cost of cleaner water: Assessing agricultural pollution reduction at the watershed scale

Nonpoint source pollution in intensively managed agricultural landscapes is of great concern to the general population, farmers and policymakers, as it impacts local water quality and can have large downstream effects, as in the case of hypoxia in the Gulf of Mexico. In this study, we outline a methodology to simultaneously assess economic costs and water quality benefits associated with the hypothetical placement of a broad set of conservation practices. The study, performed for the Iowa Department of Natural Resources, assesses thirteen major subbasins in Iowa by interfacing economic models with the Soil and Water Assessment Tool model. The conservation practices analyzed include land set-aside, terraces, grassed waterways, contouring, conservation tillage, and a simple nutrient reduction strategy. Annual costs range from $300 to $597 million. Predicted sediment, total phosphorus (P), and nitrate decreases range from six to 65 percent, 28 to 59 percent, and six to 20 percent, respectively, relative to the baseline.