Extensive modifications of the landscape in the continental U.S. Great Plains and Midwest for agriculture has completely changed the hydrologic, sediment transport, and water quality characteristics of watersheds and streams in the regions. This has had profound effects on receiving water bodies downstream of extensively farmed areas: streams, rivers, lakes, and reservoirs, with erosion/sedimentation, water quality, aquatic species with increased flooding, stream instability, and impaired uses: recreation, drinking water, fishing, etc. Moreover, there is recent evidence that agricultural runoff contributes to climate change through the release of nitrous oxide, a potent greenhouse gas, in the rivers and streams that receive runoff from agricultural lands (Winnick, 2021). The broad objective of this project is to facilitate the application of Engineering with Nature (EWN) to intensively farmed areas in the Great Plains and Midwest regions. In order to design sustainable EWN infrastructure, more accurate estimates of exported nutrients and contaminants need to be developed. This project will integrate nutrient and contaminant fate and transport processes within the Gridded Surface Subsurface Hydrologic Analysis Program’s (GSSHA) in order to meet modeling needs. Products from this development effort will greatly enhance the ability of the USACE to assess potential applications of EWN features in extensive agricultural settings. In addition to assessment, the tool will be useful for engineering design and implementation of EWN features in watersheds containing USACE-managed water bodies.
