Applicability of Current Theories of Flow in Leaky Aquifers

The applicability of current theories of flow in leaky aquifers has been investigated using new analytic and numeric solutions. In general it has been customary to use one or both of the following assumptions: (1) storage in the aquitards is negligible, and (2) drawdowns in the unpumped aquifers remain zero. At small values of time the first assumption amounts to neglecting the effects of leakage completely. Errors introduced in this way can become significant when the β factor of Hantush exceeds 0.01. It appears that β may exceed 0.1 in many field situations. At large values of time, neglecting drawdowns in the unpumped aquifers can also lead to serious errors unless the transmissibilities of these aquifers are significantly greater than that of the pumped aquifer. In addition present methods of analyzing leaky aquifers usually rely only on drawdown data from the pumped aquifer. In our opinion such an approach is not sufficient to characterize a leaky system; current methods of analyzing field data from leaky aquifers need to be improved.