Hydrologic restoration of a groundwater-fed sedge meadow wetland in south-central Wisconsin

The design of aquatic restoration projects was investigated in the specific example of drained sedge meadow wetlands in the Nine Springs complex of Fitchburg and Madison, Wisconsin. Intact wetlands in that complex are fed by extraordinarily constant groundwater inflows, manifested by essentially recessionless flows in adjacent springs. A high water table and a well-developed capillary fringe maintain saturated conditions nearly to the ground surface throughout the growing season in the intact wetland studied. In the drained wetland studied a lower water table and the lack of a significant capillary fringe result in considerably drier conditions late in the growing season despite early season inundation. An experiment was devised to evaluate whether restoring wetter conditions would be sufficient to allow the reestablishment of a sedge meadow plant community on the drained site, which is currently covered by a near-monoculture of reed canarygrass (Phalaris arundinacea). Combinations of restoration strategies included physical isolation, vegetation removal and irrigation with either well water or tertiary-treated sanitary effluent. Although vegetation removal and wetter conditions reduced the ability of the reed canarygrass to reestablish, none of the tested restoration conditions were sufficient to prevent its reestablishment by the end of the second growing season. Data analysis suggests that sustained water levels within 10 cm of the ground surface may be the hydrologic condition that could control reed canarygrass reestablishment. A continuous hydrologic model was developed to investigate the potential for stormwater to support a wetland restoration. Approaches such as continuous modeling are necessary to evaluate potential restoration designs for the performance characteristics relevant to aquatic ecosystem functions, which generally concern factors such as the frequency, timing and duration of specific flow or water level conditions.