Approaches of soil data aggregation for hydrologic simulations

Abstract

This study presents a comprehensive investigation of the State Soil Geographic Database (STATSGO) and the Soil Survey Geographic Database (SSURGO) soil databases for their applications in hydrologic modeling practices, and provides detailed instructions on soil data aggregation. Two types of soil data aggregations are developed and improved for the preparation of soil input data: (1) spatially-based aggregation for hydrologic models which require one representative soil profile for each spatial units of modeling simulations; and (2) taxonomy-based aggregation to handle the potential edge-matching issues in SSURGO, i.e. the artificial split of a soil type by the boundary of soil survey areas. The developed approach and program were applied at the spatial scales of soil survey area and watershed in California, U.S. representing hydrologic simulation domains with areas at the magnitudes of 1000 km2 and 10,000 km2, respectively. Edge-matching issues were identified for more than 20% of the involved soil map-units for both cases, about 90% among which were handled by the proposed approach in this study. The naming inconsistency in soil taxonomy was recognized as one of the causes for remaining issues. The reductions of soil map-units and components numbers before and after the aggregation are less than 10%, indicating that the proposed procedure has the capability to effectively handle the edge-matching issues while maintaining spatial resolution of the soil data.