Abstract: Excess fertilizer nutrients entering Midwestern agricultural streams degrade both local and downstream water quality, resulting in algal blooms and subsequent hypoxic ​“dead zones” occurring annually in Lake Erie and the Gulf of Mexico. Large-scale implementation of conservation practices and alternative practices (e.g., bioenergy landscapes) that effectively prevent excess nutrients from entering downstream waterways while maintaining productive agriculture is critical for managing water quality.

Watershed models are critical tools for assessing watershed-scale implementation and as such can guide effective management. In this talk, I will discuss a project in which we evaluated implementation of inset floodplains (“two-stage ditch”) in formerly channelized waterways in the River Raisin Watershed (RRW), a major subbasin in the Western Lake Erie Basin. Empirical measurements for nutrient reductions from two-stage ditches across the Midwest were combined with output from a soil water assessment tool (SWAT) model. We modeled two-stage implementation in 25, 50, and 100% of headwater reaches in the RRW and found that the practice could reduce total annual NO₃--N export by 2, 5 and 10%, respectively. The two-stage was even more effective at reducing total phosphorus export, which was reduced by 12, 20 and 31%, respectively.

I will then discuss preliminary results of a LDRD project at Argonne that is assessing the influence of large-scale implementation of bioenergy crops on marginal land formerly planted in corn and soybeans on water quality in Illinois watersheds. High-resolution results will be used in an economic analysis at the county and state levels to estimate the total costs and benefits of conservation practices.