Type curves derived from Theis' exact nonequilibrium well function solution are proposed for graphical estimation of aquifer hydraulic properties, transmissivity (T), and storage coefficient (S), from water-level recovery data after cessation of a constant-rate discharge test. Drawdown (on log scale) is plotted versus the ratio of time since pumping stopped to duration of pumping, a normalized time. Under Theis conditions, individual type curves depend on only the dimensionless pumping duration, which depends in turn on S and radial distance from the pumping well. Type curve matching, in contrast to the Theis procedure for pumping data, is performed by shifting only the drawdown axis; the time axis is fixed because it is a relative or normalized time. The match-point for the drawdown axis is used to compute T, and S is determined from matching the curve shape, which depends on early dimensionless-time data. Multiple well data can be plotted and matched simultaneously (a composite plot), with drawdown at different radial distances matching different curves. The ratio of dimensionless pumping durations for any two matched curves is equal to one over the squared ratio of radial distances. Application to two recovery datasets from the literature confirm the utility of these type curves in normalized time for composite estimation of T and S.

Composite recovery type curves in normalized time from Theis' exact solution

Presents a review on implementing finite element methods on supercomputers, workstations and PCs and gives main trends in hardware and software developments. An appendix included at the end of the paper presents a bibliography on the subjects retrospectively to 1985 and approximately 1,100 references are listed.

Implementing finite element methods on supercomputers, workstations and PCs: a bibliography (1985‐1995)

A previously described finite element model for analyzing the effects of pumping and recovery in deep aquifers has been implemented on a micro‐computer. The system includes the effects of leaky aquifers, wellbore storage, skin effects at the well, and single or multiple impervious or recharge boundaries. The recovery of pressure following the cessation of flow into the well is plotted against an inverse function of time (θ). The shape of the curve can be related to values of the parameters describing the hydrogeologic properties. By iteratively modifying the parameters of the model, the engineer can develop a representation of a porous soil or rock layer that is consistent with the results of the pumping tests. Examples show how each parameter affects the calculated results. Applying the model to three sets of tests in deep rock formations shows that consistent results are obtained but that the match between the field data and the computed results is sometimes quite approximate. Nevertheless, the model gi...

Evaluation of Deep Pumping Tests

Hydrogeologic parameters can be estimated from the observed recovery of pressure during pumping tests in deep strata, but the computations are tedious and may be limited by the availability of analytical solutions. PC PUMPING is a computer program, based on finite element methods, that can accommodate both constant and variable material properties, several distinct aquifers, arbitrary histories of pumping and recovery, leaky aquifers, wellbore storage effects, skin effects, and the presence of planar and circumferential boundaries. The program runs on a microcomputer. Solutions are obtained by iterative matching of modeled to actual pressure recovery curves. A menu‐driven system of input and direct graphical output to either CRT screen or pen plotter have greatly reduced the time required to analyze the results of pumping tests, and several hydrogeologists who have had little previous experience with computers are now using the system. The paper also discusses several issues of development and documentation.

Denise Wilton Tripp

Papers

Finite Element Microcomputer Well Drawdown System

Evaluation of Deep Pumping Tests