Using an Interdisciplinary Approach to Assess Effects of Agricultural Best Management Practices on Stream Health

Despite increasing numbers of best management practices (BMPs) being installed on agricultural landscapes and billions of dollars spent on BMP programs, stream health continues to decline in Virginia due to agricultural nonpoint-source pollution. The efficacy of BMPs for restoring stream health is influenced by a complex suite of biophysical factors and is ultimately constrained by landowner participation in cost-share programs. We seek to understand BMP efficacy using an interdisciplinary approach involving watershed modeling, examination of ecological responses to BMP installation, and assessments of landowner behaviors and perspectives regarding BMP programs. We used the Soil and Water Assessment Tool (SWAT) to model sediment and nutrient yields to streams in the Clinch, Powell, and Holston river watersheds in Virginia. The SWAT model revealed critical source areas of pollutants, and we used those results to select watersheds representing gradients of pollutant loading and BMP implementation. We collected data from the 31 selected watersheds on benthic macroinvertebrate communities, benthic habitat quality, and water quality from 2019–2021 to test for effects of BMPs on stream health. A path analysis indicated that BMPs did not directly influence stream health. We are conducting mail surveys in the same watersheds chosen for the assessment of stream health to determine factors that lead to landowner persistence in BMP programs after cost-share contracts end. Finally, we will integrate the social and ecological information to design plausible BMP installation scenarios that assess effects of increasing persistence, increasing adoption, or changing the types of BMPs adopted on stream health. Our results will provide managers with maps of critical-source areas where BMP placement is most needed, recommendations for the most appropriate BMPs depending on landscape conditions, and tools for effectively encouraging landowner persistence at the conclusion of cost-share programs.