ASM
Numerical Aquifer Simulation Model

Version: 5.0E (April 1995)
Order No: BAS 27
Price: Contact igwmc@mines.edu for more info

ASM (Aquifer Simulation Model) is a numerical model for two-dimensional horizontal or vertical simulation of ground-water flow and solute transport problems. The flow equation is solved using a node-centered finite difference method. The system equations can be solved with the iterative alternating direction implicit method (IADI) or two variants of the preconditioned conjugate-gradient method (PCG). Automatic calibration of steady-state flow fields are supported using the Marquardt-Levenberg method. Pathlines and isochrones for steady-state flow fields are computed by Euler integration. Two different schemes of velocity interpolation are available, using the methods by Prickett (used in the Random Walk solute transport model) and by Pollock (included in the MODPATH model).

Solute transport is simulated by the random-walk method and includes transverse and longitudinal dispersion, molecular diffusion, linear retardation, and first-order decay. Sources can be either permanent or instantaneous. The program handles both steady-state and transient flow under confined, phreatic, or leaky-confined conditions. Transport is based on a steady-state flow field. The aquifer can be heterogeneous and anisotropic. Options are available for time-varying pumping and injection rates in wells, temporally and spatially variable recharge, permanent or instantaneous solute injection, and infiltration of exfiltration of surface water. The model supports a grid of up to 80 X 80 cells, includes a detailed water balance, and provides utilities for comparison of measured and computed heads, and generation of stochastic hydraulic conductivity or transmissivity distributions.

ASM has a menu-driven, interactive user-interface program. The program includes various on-screen graphical options including head contours, concentration distribution, velocity vectors, pathlines, isochrones, breakthrough curves, parameter distributions, and imported DXF files. Output includes spatial distribution of heads and concentrations, time series for heads, and breakthrough curves in HPGL format, and ASCII results files for postprocessing with a commercial graphics program.

ASM is distributed on DOS-formatted disks containing source codes, runtime version, and example files. The ASM user's manual includes installation and operation instructions, and example problems. ASM is a proprietary program.

SYSTEM REQUIREMENTS

Intel 80i86 based computer or compatible 570 Kb free RAM (80386/87 and 4 Mb RAM for some options) 2.5 Mb free disk space
DOS 3.1 or higher
EGA or VGA graphics

Developers of ASM: W. Kinzelbach (ETH, Switzerland), and R. Rausch (University of Stuttgart).