Effects of subsurface soil characteristics on wetland–groundwater interaction in the coastal plain of the Chesapeake Bay watershed

Abstract

Ecosystem services provided by depressional wetlands on the coastal plain of the Chesapeake Bay watershed (CBW) have been widely recognized and studied. However, wetland–groundwater interactions remain largely unknown in the CBW. The objective of this study was to examine the vertical interactions of depressional wetlands and groundwater with respect to different subsurface soil characteristics. This study examined two depressional wetlands with a low‐permeability and high‐permeability soil layer on the coastal plain of the CBW. The surface water level (SWL) and groundwater level (GWL) were monitored over 1 year from a well and piezometer at each site, respectively, and those data were used to examine the impacts of subsurface soil characteristics on wetland–groundwater interactions. A large difference between the SWL and GWL was observed at the wetland with a low‐permeability soil layer, although there was strong similarity between the SWL and GWL at the wetland with a high‐permeability soil layer. Our observations also identified a strong vertical hydraulic gradient between the SWL and GWL at the wetland with a high‐permeability soil layer relative to one with a low‐permeability soil layer. The hydroperiod (i.e., the total time of surface water inundation or saturation) of the wetland with a low‐permeability soil layer appeared to rely on groundwater less than the wetland with a high‐permeability soil layer. The findings showed that vertical wetland–groundwater interactions varied with subsurface soil characteristics on the coastal plain of the CBW. Therefore, subsurface soil characteristics should be carefully considered to anticipate the hydrologic behavior of wetlands in this region.

Water‐Soluble Organic Matter From Soils at the Terrestrial‐Aquatic Interface in Wetland‐Dominated Landscapes

“…It is estimated that there are 17,000 Delmarva Bays on the Peninsula; however, only 29% retain natural vegetative cover as the bays have been impacted by agriculture and historical ditching (Fenstermacher et al, 2014). Delmarva Bays alternate between gaining in the spring and losing conditions in the fall (Phillips & Shedlock, 1993), and previous studies have documented the variable surface connectivity of Delmarva Bays to local streams (Epting et al, 2018;Lee et al, 2019Lee et al, , 2020. These surface water-groundwater interactions also influence water chemistry in Delmarva Bays where groundwater collected near the edge of Delmarva Bays shares similar characteristics to the surface water, such as low pH, decreased alkalinity, and high dissolved aluminum concentrations (Phillips & Shedlock, 1993).…”

Detecting causal relationship of non-floodplain wetland hydrologic connectivity using convergent cross mapping

“…If a piezometer was distant to a well, the lagged response of GW to NFW might be observed. However, the subsurface soil characteristic greatly affected the vertical water transport from NFW to GW 30 . When groundwater flow direction was not clear, measurements from a piezometer might not be associated with those from a well away from a piezometer.…”

“…To see the interactions between the surface and groundwater, a well and piezometer were installed side by side (Fig. S1 of the Supplementary Material) since different soil conditions under the bottom of NFW might not correctly capture their interactions 30 .…”

“…2 ). The well and piezometer in the NFW was installed to 0.9 and 3.0 m below the wetland bottom, respectively, and they were spatially close each other 30 . Following similar previous studies 7 , 30 , this study assumed the water levels monitored by a well and piezometer indicated NFW and GW , respectively.…”

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

“…GIWs, or wetlands that are surrounded by uplands and lack obvious connection to surface water, often interface with groundwater and have been found to provide functions such as nutrient uptake, ecological habitat, flow generation, sediment retention, and groundwater recharge (Cohen et al, ; Lane et al, ; Leibowitz et al, ; McLaughlin, Kaplan, & Cohen, ; Rains et al, ; Tiner, ). Perched groundwater in GIWs collects on top of a low hydraulic conductivity unit and exchanges water with the GIW (Brooks, ; Golden et al, ; Lee et al, ; Melly, Schael, & Gama, ; Rains et al, ; Sitzia, Gayo, Sepulveda, & Gonzalez, ). The importance of GIW interaction with perched aquifers has recently been recognized as it can sustain surface water levels independently of regional aquifer fluctuations and control nutrient fluxes to GIWs (Rains et al, ).…”