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

Abstract

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. K E Y W O R D SAppalachian Plateau, geographically isolated wetlands, groundwater surface water interaction, hydrogeomorphology, hydroperiod, hydroregime, vernal pool, wetland

Geomorphological and meteorological drivers of ephemeral pond hydrology in the Canadian shield forest

“…Groundwater recession rates were calculated only after the pond became dry and include recessions that lasted longer than 48 hours after a water level increase. Normalized recession rates ( NRR ) were calculated following Malzone et al (2019) as the ratio between RR and potential evapotranspiration (PET). The PET was calculated using the formula from Oudin et al (2005) based on daily temperature data.…”

“…Normalized recession rates (NRR) were calculated following Malzone et al (2019) as the ratio between RR and potential evapotranspiration (PET). The PET was calculated using the formula from Oudin et al the pond emptied more rapidly than it would have if evapotranspiration were the only pond outflow:…”

“…Local studies on ephemeral pond hydrology have focused on the period following freshet during which the ponds hold water, known as the hydroperiod. Studies have reported how the ephemeral pond hydroperiod is influenced by meteorological conditions such as precipitation and evapotranspiration, as well as geographical and geological conditions such as vegetation cover, basin morphometry, topography, and geology (Bauder, 2005; Bertassello et al, 2022; Brooks, 2004; Malzone et al, 2019; Skidds & Golet, 2005). Local in‐situ studies are often based on a small number of ephemeral ponds, but some authors have conducted multi‐site studies (e.g., Bertassello et al, 2022; Skidds & Golet, 2005).…”

“…The seasonal wetlands in this region are active in the spring following snowmelt and dry in early summer. The scientific literature recognizes that although they appear to be isolated from nearby hydrosystems, ephemeral ponds are connected through runoff and groundwater flow exchanges (Bertassello et al, 2018; Hayashi et al, 2016; Malzone et al, 2019; Pyzoha et al, 2008). Ephemeral ponds are strong contributors to forest diversity.…”

“…groundwater flow exchanges (Bertassello et al, 2018;Hayashi et al, 2016;Malzone et al, 2019;Pyzoha et al, 2008). Ephemeral ponds are strong contributors to forest diversity.…”