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Groundwater influence on water budget of a small constructed floodplain wetland in the Ridge and Valley of Virginia, USA

Ludwig, Andrea L., Hession, W. Cully
Journal of hydrology 2015 v.4 pp. 699-712
wetlands, evapotranspiration, autumn, stream channels, seepage, floodplains, water table, groundwater, vegetation, prediction, Virginia
A floodplain in the headwaters of a tributary to the Chesapeake Bay, Ridge and Valley of the Eastern United States.This study investigated the influence of groundwater exchange in the annual wetland hydrologic budget and identified spatial and temporal variability in groundwater hydraulic gradients using an array of nested piezometers.Data showed that the created wetland met hydrologic success criteria, and that the wetland storage was fully connected with the groundwater table. Water-surface storage fluctuation was not fully explained by precipitation and evapotranspiration, suggesting that storage was highly influenced by groundwater inputs. The potentiometric surface showed that hillslope seep recharge was the dominant groundwater vector. However, during the summer and fall months, the adjacent stream channel was a losing system, and storm-driven rise in stream stage affected wetland storage. The complex hydrology of this relatively small wetland indicates that predicting the fluctuations of storage for design of unconfined floodplain wetlands is challenging, and that if the influence of groundwater seepage is negated, then fluctuations may be underestimated to the point of harming vegetation.