A large scale GIS geodatabase of soil parameters supporting the modeling of conservation practice alternatives in the United States

Authors: DI LUZIO, MAURO - Texas Agrilife Research; White, Michael; Arnold, Jeffrey; WILLIAMS, JIMMY - Texas Agrilife Research; Kiniry, James

Submitted to: Journal of Geographic Information System
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2017
Publication Date: 6/6/2017
Publication URL: https://handle.nal.usda.gov/10113/5801894
Citation: Di Luzio, M., White, M.J., Arnold, J.G., Williams, J.R., Kiniry, J.R. 2017. A large scale GIS geodatabase of soil parameters supporting the modeling of conservation practice alternatives in the United States. Journal of Geographic Information System. 9:267-278.

Interpretive Summary: Water quality models are used routinely for determining impacts on land use and management on water supply and quality. Models account for influence of soil characteristics on runoff, ET, plant growth, and transport of sediment and nutrients. Thus, describing the soil with appropriate soil properties is critical for accurate simulations. In this study, a large scale geodatabase of soil model parameters was developed for the United States. The soil characteristics were developed by USDA-NRCS. High resolution soil data is used when available and large scale coarse resolution data is used when the high resolution data is missing. A procedure was developed to fill in missing parameters. The geodatabase system efficiently stores spatial soil features and provides tools for extraction, spatial analysis, and mapping of parameters. The set of target models include: SWAT (Soil and Water Assessment Tool), APEX (Agricultural Policy Extender), and ALMANAC (Agricultural Land Management Alternatives and Numerical Assessment Criteria). The geodatabase and associated tools will provide the best soils data available for several commonly used water quality models. This will increase the accuracy of the models and improve our decision making capabilities.

Technical Abstract: Water quality modeling requires across-scale support of combined digital soil elements and simulation parameters. This paper presents the unprecedented development of a large spatial scale (1:250,000) ArcGIS geodatabase coverage designed as a functional repository of soil-parameters for modeling and comparison of water quality outcomes in the United States. The set of target models include: SWAT (Soil and Water Assessment Tool), APEX (Agricultural Policy Environmental Extender), and ALMANAC (Agricultural Land Management Alternatives with Numerical Assessment Criteria). This development relies on the Digital General Soil Map (DGSM) as the source of soil information, and leverages on architectural design and associated tools created for a companion product at higher resolution from which also was extended a procedure for refilling a large number of missing derived parameters. Outlined by regional watershed layouts and supported by GIS land use layers, the core product is developed using the File Geodatabase (FGDB) data structure, which brings, via customized Python-based tools, the data directly into geoprocessing workflows. The FGDB implement efficiently stores spatial soil features, tabular model elements and linked relationships, while seamlessly providing the environment for the extraction, spatial analysis, and mapping of the models’ parameters. As an alternative, the composing spatial elements, polygons and multi-resolution rasters, and the models’ elements are offered as a file-folder system of data with completely Open Source formats. Finally, this geographic database coverage provides support for the traditional large-scale and harmonized application of the models as well as an alternative to the higher resolution companion for areas where this information is still under development.