Bohling, Geoffrey C. / A ground penetrating radar study of water table elevation in a portion of Wisconsin's central sand plain
II. Geology and hydrogeology of the study area, pp. 10-18 PDF (1.9 MB)
16 elevation of the bottom of the outwash. The water table slopes from an elevation of about 1060 feet in the southern part of the study area to about 1040 feet near the river bluff. The saturated thickness of the aquifer ranges from about 70 feet in the southern part of the study area to about 40 feet near the river bluff (Kraft, in preparation). The saturated thickness and the hydraulic conductivity of the sediments determine the ability of the aquifer to transmit water laterally. A pump test in the central part of the study area (Figure 2) yielded a hydraulic conductivity for the outwash of 320 ft/day, or 0.11 cm/s (Weeks, 1969; Weeks and Stangland, 1971, p. 24). This is somewhat high compared to other pump test results in the sand plain area, apparently because the sediment is somewhat coarser in the study area than it is else- where in the sand plain (Weeks and Stangland, 1971, p. 25). The pump test results were also used to calculate a ratio of horizontal to vertical hydraulic conductivity of 7. Results of slug tests in and near observation well number 1 (Figure 2) give an average hydraulic conductivity of 0.048 cm/s (Kraft, in preparation). Slug tests typically give a lower hydraulic conductivity than do pump tests (e.g., see Muldoon, 1987), presumably because pump tests sample a larger portion of the aquifer material and therefore incorporate the effects of coarser lenses or beds. Therefore, this discrepancy in results is not too surprising.