Analysis of Data From Pumping Tests in Anisotropic Aquifers: Equations and Graphical Solutions

Traditional methods for characterizing horizontally anisotropic groundwater aquifers seek solutions in terms of a fictitious directional hydraulic parameter called directional transmissivity. But all common pumping test drawdown models respond to such conditions as though transmissivity were insensitive to direction and instead an easily identified class of ordinary hydraulic coefficients were the exclusive carriers of directional information. The failure of traditional techniques to fully exploit this universal phenomenon has resulted in the development of inflexible model‐specific anisotropy methods which are needlessly complicated, excessively prone to failure, and consequently seldom used. An alternative method presented here is based directly on these characteristic responses. It enables for the first time a choice of analytical techniques ranging from preliminary back‐of‐the‐envelope graphical anisotropy assays and manual solutions (emphasized here) to rigorous least squared error full characterizations using simple variations of just one basic approach. Unlike traditional methods which typically fail to yield meaningful information when no formal anisotropy solution is possible, the proposed method always provides a qualitative indication of horizontal anisotropy, isotropy, nonhomogeneity, or lack of sufficient data, because diagnostic data plots are constructed prior to formal analysis.