Abstract

Over 30 years ago, modelers at CDM Smith developed the nucleus of DYNSYSTEM, a suite of finite-element numerical modeling codes, for use in simulating groundwater flow and contaminant transport. DYNFLOW is a fully 3-dimensional, Galerkin finite element flow modeling code, adapted from AQUIFEM, an earlier 2-dimensional code developed at MIT. DYNTRACK is the companion solute transport code to DYNFLOW and uses the random walk method. Through the years, the initial DYNFLOW and DYNTRACK programs have been frequently updated and supplemented to include features that allow the modeler to tackle ever more demanding modeling applications. The advantages of the finite-element flow field representation have underpinned the successful application of the DYNSYSTEM codes to hundreds of model applications, including many that have posed significant technical challenges.

The basic elements of the finite element flow and random walk transport computations as implemented in DYNSYSTEM will be briefly outlined. Selected advanced computational features of DYNSYSTEM will be introduced, including sharp-interface modeling of salt-water intrusion, coupled flow-transport (variable-density, multi-phase flow), groundwater-surface water interaction, and representation of soil/crop processes as they affect transient groundwater recharge. Discussion will include practical features developed to aid the user, such as automatic rewetting of dry nodes, input/output capabilities for transient simulations, and utilities to facilitate import and export of data between the model and ArcGIS.

Brief examples of selected DYNSYSTEM finite element model applications highlighting these features will be presented, including an award-winning 1983 contaminant transport study, large-scale groundwater resource management modeling on Long Island in the 1990s, coupled flow-transport salt-water intrusion modeling of Savannah-Hilton Head, and recent examples of dual porosity solute transport, mass flux, and vadose zone vapor flow/transport simulations.