MT3DMS is a modular three-dimensional transport model that can simulate advection, dispersion, and chemical reactions of dissolved constituents. MT3DMS uses the output head and cell-by-cell flow data computed by MODFLOW to establish the groundwater flow field. GMS supports both preprocessing and postprocessing with MT3DMS. As with MODFLOW, GMS provides several ”packages” which simplify user-input. This data is then used by MT3DMS when MT3DMS is run, and the solution can then be read back into GMS for visualization. GMS has the ability to produce film loops and .avi animations as shown below. MT3DMS has the capability of modeling changes in concentrations of groundwater contaminants due to advection, dispersion, diffusion, and some chemical reactions including equilibrium-controlled linear or non-linear sorption, and first-order irreversible or reversible kinetic reactions. Additionally, MT3DMS contains three major transport solution techniques - the standard finite difference method, the particle-tracking-based Eulerian-Lagrangian methods, and the high-order finite-volume TVD method.