Abstract

The Hantush-Jacob solution was developed to predict drawdowns in a leaky aquifer system on the basis of several restrictive assumptions, one of which is that the horizontal hydraulic conductivity (K_r) is equal to the vertical hydraulic conductivity (K_z) in the aquifer (K_r= K_z). This assumption is true only for very rare cases. When K_r ≠ K_z, determined aquifer and aquitard parameters may have uncertainties. This paper analyzes the reliability of the calculated horizontal hydraulic conductivity K_r and storage coefficient S in the aquifer and the vertical hydraulic conductivity K′ in aquitard when the Hantush-Jacob solution is used to analyze pumping test data. One hypothetical time-drawdown data set and another data set from a pumping test were analyzed using the solution. Results from both examples indicate that the K_r and S values are affected very slightly but the K′ value can be very unreliable if K_r ≠ K_z in the aquifer. K′ from the Hantush-Jacob solution is underestimated if K_r> K_z and overestimated if K_r < K_z. The later Hantush solution accounts for the effect of aquifer anisotropy (K_r ≠ K_z) on drawdowns and is able to provide more reliable K′ values.