The RANDOM WALK technique is outlined for studying mass transport problems dictated by analytical formula driven groundwater flow distributions. This is simpler than developing a finite-difference or finite-element flow model as input to a mass transport techniques. More complex flow problems and the application of the RANDOM WALK technique to finite-difference flow models have been included in the manuals.

The RANDOM WALK technique involves representing chemical concentration of constituents by a discrete number of particles. Each of these particles is moved and dispersed by groundwater flow and is assigned a mass which represents a fraction of the total mass of the chemical constituent involved. As the number of particles gets large and approaches the molecular level, an exact solution to the actual chemical distribution is obtained.

The model includes the capabilities of including both steady and non-steady conditions, multiple pumping or injecting wells at time-variable rates, regional and uniform water-level variation velocities, homogeneous and isotropic aquifer conditions, image-well theory for simulating constant head and no-flow boundaries, and a series of sinks that can replicate a fully-penetrating and meandering river or stream.

Mass transport capabilities are accomplished by the RANDOM WALK theory given by T.A. Prickett, T.G. Naymik, and C.G. Lonnquist, 1981 and includes the full capability of mapping the concentrations of chemical constituents as they advect and disperse in the aquifer under study. Maps and computer files of concentration distribution plus tables of purge well concentrations are included. Chemical retardation, ion exchange mechanisms, and first-order degradation are included. Application of this model can be widespread, particularly in preliminary modeling analysis, auditing checks on more sophisticated models, and in learning the RANDON WALK technique.

It includes an analytical version of the Random Walk model and 8 problem sets demonstrating how the random walk technique works. The accompanying manual explains the theory, includes case studies, and documents the problem sets. Appendices cover calculations of mass, description of typical input parameters, contouring, a discussion of advantages/disadvantages of the method, and a listing of the source code.

SYSTEM REQUIREMENTS

Intel 80i86 based computer with math coprocessor, 4 MB RAM, 1 Mb Hard drive space with about 2 Mb free disk space for code and examples, DOS 5.0, VGA graphics.