Marine Resistivity as a Tool for Characterizing Zones of Seepage at Lake Lacawac, PA

Abstract

The groundwater-surface water exchange zones of lakes and streams are dynamic and difficult to characterize. The spatial variability of seepage zones makes them difficult 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.

Boat-towed radio-magnetotellurics — A new technique and case study from the city of Stockholm

“…The measurements were performed by a boat towing an array of 12 electrodes with a dipole-dipole electrode configuration. Heaney et al (2007) and Nyquist et al (2009) show a case study using multiple resistivity surveys at Lake Lacawac, in northeastern Pennsylvania. They use two types of resistivity surveys, a continuous resistivity profil-ing in which a multielectrode cable was towed parallel to the shore to image spatial resistivity variations in a lake and a follow-up resistivity data acquisition using cables laid on the lake bottom perpendicular to the shoreline.…”