MORPHOLOGICAL CONTROL OF SEASONAL AND SUB-SEASONAL GROUNDWATER FLOW IN GEOGRAPHICALLY ISOLATED WETLANDS

Geographically isolated wetlands are important upland ecosystems that provide spawning ground for amphibian species and water for vegetation. The hydroperiod of isolated wetlands is highly variable in space and time, making the quality of such ecosystems hard to predict. An often unknown component of these systems is groundwater, which may provide drought resilience by sustaining surface water levels and contributing extra water to forest vegetation. In this research the impact of wetland morphology on seasonal and sub-seasonal groundwater water levels is characterized by: (1) monitoring groundwater and surface water in three geographically isolated wetlands in the Daniel Boone National Forest, Kentucky over a range of different slopes for one year (2) Quantifying the physical properties of the aquifers and groundwater evapotranspiration rates, and (3) Numerically modeling the spring recharge rate required to sustain groundwater levels by analytic element method. Wetlands were compared on the basis of slope because slug tests indicated that each wetland had similar hydraulic conductivity, although watershed size did vary. The wetland with the highest slope had shorter spring inundation periods and was always observed to be losing water from the wetland to groundwater. Conversely, the wetland with the lowest slope had the longest period of inundation and was observed to fluctuate between gaining and losing conditions. Sub-seasonally, aquifers with shallow slopes recharged frequently in response to storms and provided groundwater to vegetation for 14-20 days as opposed to 2-4 days for steeper slopes. Calibrated numerical results indicated an average spring recharge rate of 0.0025 m/d.