The study of well hydraulics took a leap forward when Theis (1935) published his seminal work presenting a mathematical model and graphical “type curve” method for determining hydraulic properties of confined aquifers from time-drawdown data measured during aquifer (pumping) tests. Cooper and Jacob (1946) later devised a simpler graphical method based on the Theis model that only involves fitting a straight line rather than a type curve to the data. These methods, while powerful, are limited by underlying assumptions such as infinitely extensive confined aquifers, fully penetrating wells and infinitesimal well radius. Eventually new analytical solutions appeared in the literature which removed many of the limiting assumptions of the Theis model. Some methods (e.g., Hantush and Jacob 1955; Neuman 1972) lend themselves to traditional methods of analysis using type curves. Other more complex methods, however, are not well suited to graphical analysis due to the large number of type curves required for their application (e.g., Neuman and Witherspoon 1969; Moench 1984).

With the ever-increasing power of computers and software, it has become practical to use even the most sophisticated methods (e.g., variable rates, multiaquifer systems, horizontal wells, fractured wells, strip aquifers) for the evaluation of aquifer test data. Modern software packages provide graphical diagnostic tools such as derivative analysis to (1) identify important features such as wellbore storage, wellbore skin and boundary effects and (2) guide the selection of appropriate solution methods. In addition to facilitating traditional curve matching through the user interface, these packages can incorporate automatic curve fitting to optimize the match between a solution (i.e., type curve) and time-drawdown data with the added benefit of providing statistical measures of model fit (e.g., confidence intervals and significance tests). Thus, a modern approach to aquifer test analysis should take advantage of the power afforded by today’s specialized software.