This raster provides an estimate of the wetland water regimes in Iowa, prior to the implementation of drainage systems. These estimates are based on the spatial information in the USDA-NRCS gSSURGO database and soil series characteristics described in the official soil series descriptions (OSD). Soil series characteristics were matched as best as possible to the condition descriptions for the National Wetland Inventory’s defined water regimes. Soil properties and conditions described in the OSD are assumed to still be a reasonable estimate of the natural, undrained condition of the respective soils. This assumption is based on the fact that many soil properties that indicate past hydrologic conditions tend to persist over decades. Also, it is likely that some human memory of the landscape assisted in the description of soil series because determining past environmental conditions is important to understanding soil formation processes. It helps that much of the soil surveying occurred within 100-150 years after widespread use of drainage systems in Iowa. However, it should be noted that the more time between the pre-settlement conditions and when the soil was surveyed, the more likely the soil properties are to begin reflecting modern environmental conditions.
Miller, B.A., W.G. Crumpton, and A.G. van der Valk, 2009. Spatial distribution of historical wetland classes on the Des Moines Lobe, Iowa. Wetlands 29:1146-1152. doi: 10.1672/08-158.
Soil Survey Staff. 2014. Official Soil Series Descriptions (OSD). United States Department of Agriculture, Natural Resources Conservation Service. https://soilseries.sc.egov.usda.gov/osdname.asp
Soil Survey Staff. 2014. Gridded Soil Survey Geographic (gSSURGO). United States Department of Agriculture, Natural Resources Conservation Service. http://datagateway.nrcs.usda.gov