Assessing and Extending Geospatial Best Management Practice Placement Tools for Agricultural Watersheds

Open Access
- Author:
- Respess, Zachary
- Graduate Program:
- Soil Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- October 22, 2019
- Committee Members:
- Jonathan M Duncan, Thesis Advisor/Co-Advisor
Anthony Robert Buda, Committee Member
Peter J A Kleinman, Committee Member
Douglas Alan Miller, Committee Member
David Eissenstat, Program Head/Chair - Keywords:
- Water Quality
Agricultural Best Management Practices
Best Management Practices
BMPs
Watershed Planning
ACPF
Agricultural Conservation and Planning Framework
Hydrology - Abstract:
- There has been a recent push to conduct spatially explicit watershed planning at finer spatial scales to mitigate diffuse pollution. Within these targeted areas, it is best to identify locations that contribute disproportionate amounts of nonpoint source nutrient loading in order to promote cost-effective mitigation strategies. The Agricultural Conservation and Planning Framework (ACPF) helps place a collection of agricultural best management practices (BMPs) in or adjacent to agricultural fields using high-resolution soils and elevation data. This spatially explicit approach better represents runoff and nutrient pathways, but the recommendations produced by the ACPF are influenced by the properties of the digital elevation model (DEM) that is used. Features derived from a DEM are sensitive to changes in horizontal resolution. Similarly, any error in the delineated flow network will propagate through to model outputs. This thesis assesses differences in BMP siting by ACPF across three DEM resolutions in three agricultural catchments across differing physiographic regions (Ridge and Valley, Piedmont, Coastal Plain) of the Mid-Atlantic region of the United States. BMPs including grassed waterways, contour buffer strips, and water and sediment control basins were used in these test scenarios to document frequency and accuracy of placement. Significant factors governing the frequency and placement of BMPs are discussed. Some BMPs are sited based on discrete landscape attributes, while others are sited based on statistical distributions of terrain metrics. Even when keeping input parameters constant, the frequency of some BMPs varied dramatically with different DEM resolution and across physiographic regions. For example, grassed waterways that are sited using terrain distributions had an order of magnitude more potential locations in the coastal plain watershed. Contour buffer strips, which are sited on discrete slope values, were placed more consistently across physiographic provinces when holding siting criteria constant. These findings can help inform aggregation-based methods of basin-wide planning, where implementation is directed across dozens to hundreds of small management units. Results from BMP placement were then further investigated for the coastal plain watershed to demonstrate how the precision conservation workflow could be integrated into water quality planning.