OFR 03-426

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Langevin, C.D., Shoemaker, W.B., and Guo, Weixing, 2003, MODFLOW-2000, the U.S. Geological Survey Modular Ground-Water Model–Documentation of the SEAWAT-2000 Version with the Variable-Density Flow Process (VDF) and the Integrated MT3DMS Transport Process (IMT): U.S. Geological Survey Open-File Report 03-426, 43 p.


SEAWAT-2000 is the latest release of the SEAWAT computer program for simulation of three-dimensional, variable-density, transient ground-water flow in porous media. SEAWAT-2000 was designed by combining a modified version of MODFLOW-2000 and MT3DMS into a single computer program. The code was developed using the MODFLOW-2000 concept of a process, which is defined as “part of the code that solves a fundamental equation by a specified numerical method.” SEAWAT-2000 contains all of the processes distributed with MODFLOW-2000 and also includes the Variable-Density Flow Process (as an alternative to the constant-density Ground-Water Flow Process) and the Integrated MT3DMS Transport Process. Processes may be active or inactive, depending on simulation objectives; however, not all processes are compatible. For example, the Sensitivity and Parameter Estimation Processes are not compatible with the Variable-Density Flow and Integrated MT3DMS Transport Processes. The SEAWAT-2000 computer code was tested with the common variable-density benchmark problems and also with problems representing evaporation from a salt lake and rotation of immiscible fluids.



New Features in SEAWAT-2000
Purpose and Scope
Descriptions of New or Modified Processes
Global Process
Simulation Modes and Process Compatibility
Program Flow
Spatial Discretization
Temporal Discretization
Coupling of Flow and Transport
Variable-Density Flow Process
Use of Head and Equivalent Freshwater Head in SEAWAT-2000
Variable-Density Ground-Water Flow Equation
Required and Optional Flow-Related Packages Included in This Report
Basic (BAS6) Package
Internodal Conductance Packages
Source-Term Packages
Time-Variant Constant-Head (CHD) Package
Solver Packages
Link-MT3DMS (LMT6) Package
Integrated MT3DMS (IMT) Transport Process
Solute-Transport Equations
Solute-Transport Packages
Observation (OBS) Process
Input Instructions
Global (GLO) Process Input Instructions
Name (NAM) File
Discretization (DIS) File
Variable-Density Flow (VDF) Process Input Instructions
Variable-Density Flow (VDF) Process Input File
Special Considerations for the Basic (BAS6) Package, Output Control (OC) Option, Internodal Conductance Packages, and Time-Variant Constant-Head (CHD) Package
Variable-Density Source-Term Packages and Use of Auxiliary Variables
Solver Packages
Integrated MT3DMS Transport (IMT) Process Input Instructions
Observation (OBS) Process Input Instructions
Running SEAWAT-2000
Benchmark and Example Problemsv
Salt Lake Problem
Rotation of Three Immiscible Fluids
Demonstration of Different Modes Using the Henry Problem
Classic Henry Problem—Coupled Variable-Density Flow and Solute Transport
Variable-Density Flow without Solute Transport
Uncoupled Variable-Density Flow and Solute Transport
Variable-Density Flow Coupled with Dual-Domain Transport
References Cited