Time Domain Electromagnetic Induction Survey of the Sandstone Aquifer in the Lake Winnebago Area

Background/Need The Cambrian and Ordovician sandstone aquifer of eastern Wisconsin is a major source of water for municipalities and industry in eastern Wisconsin. This aquifer has been developed heavily in the Lake Winnebago area, particularly along the northern and southern ends of the lake. The rate of development has intensified over the last decade in response to strong economic growth and an increase in the population of the City of Fond du Lac and the developed corridor from Neenah to Kaukauna and surrounding areas (The Fox Cities). Declining water levels and deteriorating water quality has created concerns over the long term viability of the aquifer.

Objectives The objective of this study is to perform the first regional Time Domain Electromagnetic  Induction (TEM) survey of sandstone aquifer around Lake Winnebago. The data goal is to map the thickness of the Cambrian and Ordovician Sandstone aquifer and identify areas of saline ground water. The results of this study will provide critical information needed by several water utilities to make informed water supply planning decisions.

Methods A geophysical survey consisting of 55 TEM soundings was conducted in Fond du Lac, Winnebago, Outagamie, and Calumet Counties using a Geonics EM57 system. The layout of the soundings was optimized to measure the electrical resistivity of the sandstone aquifer at depths of about 500 to 1,000 feet. The data were interpreted using the TEMIX two-dimensional modeling software by Interpex. Ltd.