Assessment of electrical resistivity method to map groundwater seepage zones in heterogeneous sediments

Underwater electrical-resistivity data were collected along the southwest shore of Mirror Lake,<br>NH, as part of a multi-year assessment of the utility of geophysics for mapping groundwater seepage<br>beneath lakes. We found that resistivity could locate shoreline sections where water is seeping out of<br>the lake. A resistivity line along the lake bottom starting 27-m off shore and continuing 27-m on shore<br>(1-m electrode spacing) showed the water table dipping away from the lake, the gradient indicative of<br>lake discharge in this area.