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 …Continue reading “Pre-settlement Water Regimes of Iowa Wetlands”
The water regimes of contemporary wetlands when compared to their historic regimes suggest that many of today’s wetlands have different water regimes than they did prior to the onset of drainage. Because of the regional lowering of the groundwater table, many of today’s wetlands have drier water regimes, but some have wetter water regimes because they receive drainage tile inputs. Our results indicate that restoration has favored the wettest classes of wetlands and that temporarily to saturated wetland classes have not been restored in proportion to their relative abundance in the pre-drainage landscape.
We estimated the pre-settlement density and area of different classes of palustrine wetlands on the Des Moines Lobe based on soil characteristics. Prior to drainage, wetlands covered nearly half of the Des Moines Lobe and there were differences in both the types and relative abundance of wetlands among the four geologic subdivisions of the Lobe (Bemis, Altamont, and Algona till plains and Altamont Lake).
Nitrate concentration and stream discharge data from USGS National Stream Quality Accounting Network monitoring stations in the upper Mississippi River (UMR) and Ohio River basins were used to calculate stream nitrate loading and annual flow-weighted average (FWA) nitrate concentrations. The model accounts for 90% of the variation among stations in long term FWA nitrate concentrations and was used to estimate FWA nitrate concentrations for a 100 ha grid across the UMR and Ohio River basins. To estimate potential nitrate removal by wetlands across the same grid area, mass balance simulations were used to estimate percent nitrate reduction for hypothetical wetland sites distributed across the UMR and Ohio River basins. Modeling results suggest that a 30% reduction in nitrate load from the UMR and Ohio River basins could be achieved using 210,000-450,000 ha of wetlands targeted on the highest nitrate contributing areas.