Effects of Surrounding Water Table on a Forested Wetland Habitat in East Coast of Virginia

Exchanges into and out of a wetland, including surface water flow, groundwater flow, and constituents in the flows, usually determine the wetland physicochemical characteristics and biodiversity. To date, of these three exchanges, groundwater flow is the least studied, particularly in the United States of America. In this thesis, field observations were conducted at a forested non-tidal wetland, located on a flat hilltop. The position of the wetland is such that groundwater outflow is the only significant exchange that could be impacted by the surrounding land use. In addition, a spatially variable steady-state model was set up to extrapolate the observations to examine the effects of groundwater flow on the wetland. The model consists of: 1) the stratified unconfined aquifer underlying the wetland; 2) a ditch near the border of the wetland bearing a certain water level (a boundary condition in the model); and 3) recharge from periodic rainfall. The aquifer is relatively thin and where the water table is below the wetland ground surface there is an overall descent of water table toward the ditch. The model was calibrated and validated using the observed data, and then used to predict the distance from the ditch, beyond which the influence of the ditch on the aquifer will become negligible. Herein, the purpose was to determine whether the ditch is hydraulically connected with the wetland. This model can be an effective tool for analyzing groundwater effects on, and assessing the resilience of, the wetland. The results will be useful for protecting the wetland from its surrounding developments