Theme Overview: Agriculture and Water Quality in the Cornbelt: Overview of Issues and Approaches

More than three decades have elapsed since the passage of the Federal Water Pollution Control Act with its stated goal of zero discharge of pollutants into the nation’s waterways. Yet, water quality remains poor in many locations and considerable loading of pollutants continues. This is particularly true for agricultural sources of water pollution and is typified by the Upper Mississippi River Basin, where more than 1,200 water bodies appear on the current U.S. Environmental Protection Agency (EPA) listing of impaired waterways. Additionally, nitrate export from this region has been implicated as a significant cause of the hypoxic zone in the Gulf of Mexico, which covered nearly 20,000 km 2 in 1999 and more than 17,000 km 2 in 2006 (http://www.epa.gov/gmpo/nutrient/hypoxia_pressrelease. html). Although a substantial body of evidence on the effectiveness of agricultural conservation practices on water quality continues to be developed, the net effect of these programs and practices at the watershed scale is unclear. Increasingly, studies are being focused on the watershed (or landscape) scale and complex interactions between agricultural practices and inputs, the types and configuration of conservation practices on the landscape, and the resulting downstream water quality. While low cost methods to reduce agricultural non-point source pollution exist, large changes in water quality in agricultural regions are likely to be costly and met with resistance. This is because to achieve large changes in water quality, major alterations to land use or installation of expensive structural practices may be required, and the costs are borne directly by producers and landowners, or by the taxpayer. Given the potentially large cost for significant improvements in water quality, it is critical to develop tools that can support cost-effective design of conservation policy and/or voluntary implementation of watershed plans focused on water quality. The following set of themed papers related to water quality and agriculture discuss these issues, with a specific focus on using integrated water quality and economic models to support better public policy and watershed-based solutions to these problems. The article following this one describes detailed field-scale data collected as part of a Conservation Effects Assessment Project supported by CSREES and ARS. In addition to assessing the effects of current conservation activities on water quality in these watersheds, data are used to calibrate a water quality model and are being integrated with economic cost information to study the optimal placement of additional conservation activities in the watershed. That article discusses the historical evolution of conservation activities in the three watersheds, the current water quality challenges in the watersheds, and the role that the integrated models can play in solving the prob