Regional trends in water-well drilling in the United States

Between the towns of Macon and Taylorville in central Illinois lies a ridge that is part of a system of ridges and knolls largely composed of sand and gravel. This ridge contains an important aquifer. An extensive electrical earth resistivity survey was conducted over the ridged-drift aquifer. Inversion of the resistivity data provided information concerning aquifer thickness and aquifer resistivity. This information, along with pump test data along the aquifer, indicated a direct and geometric relationship between aquifer resistivity and hydraulic conductivity. As a result, it was possible to better define the boundaries and water-producing capabilities of the aquifer. (Author 's abstract)