A multiscale database of soil properties for regional environmental quality modeling in the western United States

The USDA Natural Resources Conservation Service State Soil Geographic (STATSGO) database contains general soils information, but data available in STATSGO cannot be readily extracted nor parameterized to support regional environmental quality modeling. As such, each user must individually and repeatedly process data in STATSGO to obtain necessary soil properties. The objective of this study was to develop a comprehensive database, the Western States Soil Database (WSSD) (http://www.lar.wsu.edu/nw-airquest/ soils_database.html), for use in modeling regional soil and water resources and environmental quality across eight western states (Washington, Oregon, California, Idaho, Nevada, Utah, Montana, and Wyoming). We aggregated existing soil properties in STATSGO from 19,681 map units of the eight states and estimated soil properties based upon quantitative relationships among existing soil properties. The WSSD comprises 3,910 map units, with each map unit defined by 10 soil layers and each layer characterized by 31 soil properties. The WSSD was gridded to 1 and 12 km (0.62 and 7.44 mi) resolution cells for application to grid-based environmental models. Data from WSSD was tested against USDA Natural Resources Conservation Service field data and indicated satisfactory agreement; for example, the Root Mean Square Error (RMSE) for sand and clay content varied between 4% and 7%. The RMSE appeared to be greatest for organic matter and was as large as 106% of the measured value. The WSSD provides information on soil properties useful for regionalscale modeling.