Order No: BAS 04
Version: 4.01 (May 1996)
THWELLS is an analytical model for calculating the drawdown or buildup of piezometric head due to the combined effect of up to up to 100 pumping and/or injection wells. The calculation of total drawdown is based on the Theis equation or Hantush-Jacob equation for non-steady state flow in an isotropic, homogeneous confined, leaky confined or unconfined aquifer of infinite extent. The computed effects of individual wells are superimposed on a regional, horizontal or sloping ground-water surface. The model can be used for water-table aquifers for the case where the calculated drawdowns are less than half the saturated thickness of the aquifer. Boundary effects can be included through the use of image well theory.
This menu-driven, DOS-based program facilitates interactive data entry and editing. It includes tabular and graphic screen display of results. Graphic display includes both time-drawdown curves for selected locations and contour plots for a user-specified time. Data can be entered manually or from an external file, prepared in an earlier session. Results may be saved for postprocessing with a commercial graphics package. The program is proprietary to the IGWMC; distribution includes executable, and example files.
Author: P.K.M. van der Heijde (IGWMC)