This report describes the thickness and areal extent of the Sparta aquifer, identifies sands within the fresh-water extent of the aquifer, and presents data and a map that illustrate the generalized potentiometric surface (water levels) during October 1996. The report includes a detailed geophysical log, structure contour maps, hydrogeologic sections, and hydrographs of water levels in selected wells. The potentiometric surface-map can be used for determining direction of ground-water flow, hydraulic gradients, and the effects of withdrawals on the aquifer.