HYDROGEOLOGY OF A FORESTED HEADWATER WETLAND ON THE SOUTHERN MARGIN OF THE LAKE ERIE DRAINAGE BASIN

An undergraduate research project begun in Spring 2009 initiated long-term monitoring/analysis of a headwater pond and fringing wetland system in NW Pennsylvania. The project goal was to decipher and characterize the hydrologic characteristics of a perennial forested wetland over an initial study period of several months. The study site is located on the Penn State Erie – Behrend College campus which lies on the southern edge of the Lake Erie basin. The wetland lies at an elevation of ~350m MSL, has local relief of 3m, has a surface-water catchment area of ~5600m², and includes a perennial pond (1000m²; max depth 1.2m) and two seasonal wetland swales (300m²).

Within 10m of the pond perimeter, a group of three 2.5cm PVC screened monitoring wells were installed at each of the four cardinal points of the compass: a shallow (40cm) soil-profile well, a deep (80cm) glacial-till well and a combination (85cm) well. A water-level gauge was installed in the pond. The wells were designed to monitor the water table within the soil profile (~0.3m thick) and/or underlying glacial tills (>10m thick) using the tape-&-chalk method. Climatological data were collected from a weather station located 1200m from the site. Site topography was mapped using a Sokkia Set 610 Total Station and Carlson Explorer data collector, supplemented with LIDAR data.

Preliminary results suggest that the pond and wetland constitute a recharge system ~90% of the time with groundwater flowing from the pond-wetland out into the surrounding deciduous forest. Through-flow conditions were not observed. Following major rain events (>5cm/day), the groundwater flow direction reverses and the pond-wetland becomes a discharge system for up to several days. Precipitation-water table comparisons suggest an S_y of ~10% for the glacial till. The water table beneath the largest two of five catchment sub-basins responds rapidly (1-2day) and dramatically (60-80cm) to heavy (8cm/day) rainfall events.