IGWMC Software for Aquifer and Slug Test Analysis
|Order No: BAS 38|
The WELLTEST program package consists of four independently marketed proprietary and public domain programs for the analysis of pump tests and slug tests. The programs have either been developed by the International Ground Water Modeling Center, or adapted by the Center for use on personal computers. The package covers the most widely used methods for determining common hydraulic parameters for confined, leaky confined and water table aquifers. The following is a short description of each of the programs.
The program 'PUMPTEST' is a menu-driven set of interactive, DOS-based program modules for analysis of the drawdown response of a confined homogeneous, isotropic aquifer to pumping or post-pumping recovery of a constant rate, fully penetrating well. The program includes three different methods for the analysis of pumping test data, all based on the assumption that the Theis equation for depth-averaged radial-symmetric flow applies: 1) the pumped time-drawdown method (module JACOBFIT); 2) the pumped distance-drawdown method (module DISTANCE); and 3) the recovery method using time-residual drawdown data pairs (module RECOVERY). In addition, the package includes a units conversion program (module UNITS), specifically dealing with the metric and English ground-water units. The program modules automatically compute the aquifer parameters using Jacob's straight line method and the least squares method.
The program 'SLUGT' computes hydraulic conductivity values based on the analysis of slug tests. In a slug test, the water level in a well is abruptly lowered or raised and its return to equilibrium (i.e., recovery) measured for a period of time following the initial change. The change in water level is achieved by introduction or removal of a known volume of water, a solid cylinder of known volume, or by modifying the well pressure. The subsequent analysis of slug-test data is based on simple analytical models which assume radial horizontal flow in a homogeneous, isotropic aquifer. Three models commonly used for slug test analysis and included in SLUGT are: 1) Method of Cooper, Bredehoeft and Papadopulos for a confined aquifer with the well screened over entire thickness of aquifer; b) Method of Bouwer and Rice for an unconfined aquifer with the well either partially or fully penetrating the aquifer; and 3) Modified Hvorslev Method with the well either partially or fully penetrating the water table or confined aquifer.
The program 'TSSLEAK' is designed to calculate the "best" fit storage coefficient and transmissivity of a leaky confined aquifer, as well as the leakage parameters of the semi-confining layer by analyzing the aquifer response to a constant rate, fully penetrating pumping well. It fits the Hantush-Jacob equation for homogeneous, isotropic leaky aquifers to field observed pumptest data, using the method of convolution and sensitivity analysis in a least-square sense. The program can be used for analysis of drawdown data of one or more observation wells at the same time. The results include the time-drawdown pairs computed using the 'best' fit parameters, iteration progress, and the rms (root mean square) error.
The program 'VARQ' is designed to analyze the response of a confined aquifer to variable rate pumping of one or more fully-penetrating wells. It calculates the "best" fit storage coefficient and transmissivity by fitting the Theis equation to field observed pumptest data, using the method of convolution for one or more pumping wells with varying pumping rates and sensitivity analysis in a least-square sense. The program can be used for analysis of: 1) drawdown data obtained during pumping; 2) residual drawdown data obtained during the recovery period; or 3) a combination of pumping and recovery data. Constant drawdown and variable discharge data of artesian flowing wells can also be analyzed. The results of the program include the 'best' estimates for the transmissivity and storage coefficient, the time-drawdown pairs computed using the 'best' fit parameters, iteration progress, the rms (root mean square) error, and the correlation coefficient. In case the drawdown is measured in the pumping well and the observation radius is defined as the radius of the pumping well, the program can compute specific capacity.
All programs are menu-driven; results can be reviewed graphically (observed data and 'best' fit curve). The program 'PUMPTEST' includes an option to route the graphic results directly to a printer, or save them as an HPGL file for postprocessing. For the other programs, graphic results can be retained for postprocessing by using a DOS- or Windows-based screen capture utility. All programs include options to save the data for later reuse, and to save the data and results in a text file for inclusion in reports.
The programs in the WELLTEST package are DOS-applications running in conventional memory. They require: Intel 80i86 based computer with 640 Kb RAM and math coprocessor, and VGA graphics. The programs run as a DOS application under MS Windows 3.1. Optional hardware (PUMPTEST only): on-line printer, HP 7475A plotter.