A STUDY OF THE IMPACT OF DITCHPLUG RESTORATION ON THE HYDROGEOLOGY OF THE SPRAGUE RIVER MARSH, PHIPPSBURG, MAINE

The Sprague River Marsh has been periodically ditched from as early as 1716 until as late as the 1960s. In 2002, in an attempt to restore pool habitat on the surface of the marsh, the United States Fish and Wildlife Service installed a series of plugs in eleven ditches within the southern end of the marsh. One of the ditchplugs has resulted in the development of a large pool complex (approximately 14,000 square meters) on the southeast margin of the marsh. The focus of this study was to evaluate the degree to which the ditchplug restoration method has affected the hydrogeology of southern edge of the marsh. A total of fifteen monitoring wells were installed on the marsh, 9 wells in the ditchplug-pool complex (located in the southern alcove, or SA) and 6 wells in a natural pool complex (control site, located 250 m to the north in the northern alcove, NA). Fluctuations in groundwater depth, salinity, and temperature were measured for several days at a time in a set of three monitoring wells using Aqua TROLL 200 dataloggers. Two sets of data were collected from both sites, one over a small spatial scale and one over a larger spatial scale from late July to late October 2011. Land cover information, soil salinities, and slug test data were also gathered through summer and fall of 2011. Preliminary results from the small-scale well monitoring experiment indicate higher water table levels within the ditchplug-pool complex. Land cover information of this area show low marsh environments where typically high marsh environments should exist, most likely caused by increased inundation time of the plants due to increased water level behind the large ditchplug. Preliminary results from the large-scale well monitoring experiment indicate affected hydrologic flow associated with installation of the ditchplug, however it remains unclear whether the effect of this hydrologic change will negatively impact the marsh system. Further evaluation of the monitoring data is currently underway and will allow for a more accurate understanding of hydrogeologic conditions in both the northern and southern alcoves.