Marine Resistivity As A Tool For Characterizing Zones Of Seepage At Lake Lacawac, Pa
Matthew J. Heaney, Jonathan E. Nyquist and Laura E. Toran
Event name: 20th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
Session: Hydrogeophysics III
Publication date: 01 April 2007
Info: Extended abstract, PDF ( 1.54Mb )
The groundwater-surface water exchange zones of lakes and streams are dynamic and difficult to characterize. The spatial variability of seepage zones makes them hard to locate using traditional point sampling methods. The goal of this project is to use marine resistivity to identify potential zones of groundwater discharge and recharge, providing focus for point measurements. Multiple resistivity surveys were conducted at Lake Lacawac, a small, glacially formed lake in northeastern Pennsylvania. One target for these surveys was the resistivity contrast between groundwater and surface water. Another target was resistivity contrasts created by geologic heterogeneities that control groundwater discharge into the lake. Two types of surveys were conducted using a SuperSting® resistivity system. In a continuous resistivity profile, a multi-electrode cable was towed parallel to shore to look for spatial variability in resistivity around the lake. A second resistivity array was laid on the lake bottom perpendicular to the shoreline to examine how resistivity varied with distance from shore. The results of these surveys
suggested several lithology changes both along the shoreline and with distance from shore. Seepage meters were used to provide ground truth about interpreted areas of seepage.