The Role of the Floridan Aquifer in Depressional Wetlands Hydrodynamics and Hydroperiod
Blood, Elizabeth R.
Phillips, J. Scott
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Debate exists over the primary hydrologic driving variables controlling hyrdoperiod and hydrologic variation of seasonal Coastal Plain wetlands. Previous studies approached these wetlands as isolated systems and related depression's hydrology to precipitation, evapotranspiration and local surficial groundwater inflow. In the Dougherty Plain, the Floridan aquifer emerges with the aquifer water table 0 to 25 meters below the ground surface. While aquifer-emergence wetlands exist, a number of depressional wetlands exist whose surface water chemistry do not indicate direct aquifer discharge. This study focused on these depressional wetlands to determine the potential role of the aquifer on their hydrology. Ten wetlands of varying size and vegetative characteristics were studied. The wetlands were located in the lower Ichawaynochaway Creek drainage basin. Wetland hydroperiod and hydrodynamics were significantly (R2 = 0.79 to 0.93) related to Floridan aquifer level, precipitation and estimated evapotranspiration. The Floridan aquifer water elevation explained the greatest amount of the variation in the wetlands hydrodynamics and hydroperiod. The relationship between wetland pond water level and aquifer water level exhibited 3 distinct patterns (linear, concave and "broken stick"). The broken stick relationship suggested that there were critical elevations in the aquifer in which the wetland pond varied as a linear function of aquifer level then beyond that break point other factors such as temperature or precipitation were more important in wetland pond dynamics. The break point was similar among wetlands varying less than 0.5 meters.