MOCDENSE Order No: FOS 36

MOCDENSE is a two-dimensional, cross-sectional model for the analysis of saltwater intrusion. It simulates conservative solute transport and dispersion of one or two constituents in a ground-water system with density-dependent flow. The model is a modified version of the USGS-2D-TRANSPORT/MOC model by Konikow and Bredehoeft (1978), which uses finite-difference methods and the method of characteristics to solve the flow and transport equations, respectively. MOCDENSE solves for fluid pressure rather than hydraulic head because of the inclusion of variable density. The flow and transport equations are solved in a coupled fashion as the density is considered a function of the concentration of one of the constituents. It can handle varying recharge, aquifer inhomogeneities, variable aquifer thickness, and complex boundary conditions. MOCDENSE was tested on an idealized seawater-intrusion problem for which Henry (1964) developed an analytical solution. The results were nearly identical to those of other numerical models tested on the same problem.

An interactive preprocessor, PREDENSE, developed by the USGS in collaboration with IGWMC, is included with the program to facilitate user-friendly data entry and editing. This IGWMC prepared package contains two versions of MOCDENSE and its preprocessor PREDENSE:

  1. MOCD-PC accommodates a 24 by 22 finite-difference grid and 6400 particles and is compiled with Microsoft Fortran v. 5.10 to run under MS/DR DOS in conventional memory (640 Kb RAM);
  2. MOCD-EXT accommodates a 52 by 51 finite-difference grid and 25600 particles and is compiled to run under MS/DR DOS using extended memory (2.5 Mb free RAM) and as a DOS application under MS Windows 3.1.
The array size of MOCDENSE can be changed by the user by modification of the source code and recompilation of the program. Both versions of PREDENSE support a grid up to 100 by 100 nodes.

A description of the formats for the input data, a sample of input and output for a two-constituent example problem, and a listing of the FORTRAN program and updates to the code, are presented in the MOCDENSE documentation, while the operation of the preprocessor is described in a separate report.

SYSTEM REQUIREMENTS

Minimum hardware and software requirements for conventional memory version: Intel 80i86 based computer with 640 Kb RAM and math coprocessor, about 1 Mb disk space to install program, DOS 3.1 or higher.

Minimum hardware and software requirements for extended memory version: Intel 80386 based computer with 4 Mb RAM and math coprocessor, about 1 Mb disk space to install program, DOS 3.1 or higher.

Authors: W.E. Sanford and L.F. Konikow (U.S. Geological Survey).