Geomorphic controls of perched groundwater interaction with natural ridge‐top depressional wetlands

Geographically isolated wetlands (GIWs) are commonly reported as having hardpan or low hydraulic conductivity units underneath that produce perched groundwater, which can sustain surface water levels independently of regional aquifer fluctuations. Despite the potential of GIW‐perched aquifer systems to provide important hydrological and ecological functions such as groundwater storage and native amphibian habitat, little research has studied the hydrologic controls and dynamics of these systems. We compared several ridge‐top depressional GIW‐perched groundwater systems to investigate the role of watershed morphology on hydroregime and groundwater‐surface water interaction. Ridge‐top depressional wetlands in the Daniel Boone National Forest, Kentucky were chosen because they offer natural controls such as lack of apparent connection to surface water bodies, similar climate, and similar soils. Three wetlands with different topographic slopes and hillslope structures were mapped to distinguish key geomorphic parameters and monitored to characterize groundwater‐surface water interaction. Wetlands with soil hummocks and low upland slopes transitioned from infiltration to groundwater discharge conditions in the spring and during storm events. The magnitude and duration of this transition fell along a continuum, where higher topographic slopes and steeper uplands produced comparably smaller and shorter head reversals. This demonstrates that ridge‐top GIW‐perched groundwater systems are largely sensitive to the runoff‐recharge relationship in the upland area which can produce significant groundwater storage on a small‐scale.