VERTICAL LEAKANCE ESTIMATES USING MULTIPLE AQUIFER TESTS AND A MOVING-MODEL APPROACH

A new method was developed to estimate regional hydraulic properties for individual aquifers and confining units that comprise a layered system of aquifers and confining units. Production and observation wells must exist in each aquifer. Water levels are monitored in adjacent aquifers in addition to the stressed aquifer during each test. Drawdowns at each site are simulated sequentially, by test, using a radial numerical model that extends from land surface to the base of the hydrogeologic column. Conceptually, the radial model moves laterally between stress periods and re-centers on the production well used during each test. Hydraulic-property estimates for aquifers and confining units are consistent because drawdowns from all tests, representing multiple aquifers, are matched simultaneously. Vertical leakance estimates of aquifers and confining units are directly comparable to values in regional ground-water flow models. Reasonable vertical leakances were estimated through a 600 m-thick sequence of aquifers and confining units across southwest Florida with the moving-model approach. Unambiguously assigning vertical leakance estimates to multiple confining units makes this approach more applicable than individual analyses from multiple analytical solutions.