Modeling hydrologic alterations to a developing wetland in an abandoned borrow pit

Three management alternatives for modifying the duration and extent of ponding at a developing wetland in northern Texas, USA, were evaluated. These alternatives, causing minimal environmental disruption and requiring little maintenance, included installing a slurry wall to back up groundwater, raising water levels in a nearby river channel and applying water directly to the wetland. The wetland resides in a topographic depression which was created by excavating sediment for an earthen dam. The authors characterised the hydrogeology of the wetland, devised a numerical model to simulate groundwater flow and used the model to study potential hydrologic modifications to the wetland. Evapotranspiration and recharge dominate the water budget of the site. Model-calculated hydraulic head values indicated that applying water directly to the wetland elevates the water-table, while installing a downgradient slurry wall and elevating stages of nearby surface water bodies have little effect. These results suggest that diverting surface water should be an effective management technique for groundwater-fed wetlands with sediment of low to moderate hydraulic conductivity.