Investigating Hydrologic Connectivity of a Drained Prairie Pothole Region Wetland Complex using a Fully Integrated, Physically-Based Model

A fully integrated, physically-based model of a drained and farmed wetland complex in the Prairie Pothole Region of Iowa (termed Ellsworth #2) was developed to investigate hydrologic connectivity of surface and groundwater sources. The model is based on the code HydroGeoSphere, which solves surface and subsurface flow and the interaction between these domains. Physical processes governing the hydrologic response of a wetland, precipitation, plant transpiration, and surface and subsurface evaporation, were included in the model. The model was run for 6 years and predicted water table location was compared against measurements. Results indicated that intermittent ponding was observed in pothole depressions but hydrologic connectivity among three pothole depressions via surface water ponding was rarely established. Extensive subsurface tile drainage system simulated in the model removed a substantial volume of water and reduced the amount and duration of ponding. Groundwater discharge contributed to some degree during nearly all ponding events in the pothole depressions as exfiltration ranged from 1.7 to 23.6 % of annual precipitation. Despite simplifications, the model captures the interactions among hydrologic processes and provides important information for scientists and decision makers to effectively plan for current and future management of these drained and farmed wetland complexes.