Transient Aquifer Flows by Characteristics Methods

A numerical model is presented to analyze nonsteady radial flow in a finite or infinite leaky aquifer system. An equation of motion alteration, which involves the introduction of an inertia multiplier, converts the standard equations of transient ground-water flow to a form suitable for efficient solution by the method of characteristics. The result is a numerical method that should be attractively competitive in computer time usage with other numerical procedures currently in use. The equations are presented and the procedure developed for axisymmetrical flow. Several examples are used to expose the influence of the size of the distance intervals and the size of the inertia multiplier on the accuracy of the numerical process. Either constant or time-variable discharge or drawdown rates may be used as boundary conditions in infinite or bounded radial aquifer systems. Radially varying aquifer properties and leakage may also be treated.