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Environmental Fluid Dynamics Code (EFDC)

The Environmental Fluid Dynamics Code (EFDC Hydro) is a state-of-the-art hydrodynamic model that can be used to simulate aquatic systems in one, two, and three dimensions. It has evolved over the past two decades to become one of the most widely used and technically defensible hydrodynamic models in the world. EFDC uses stretched or sigma vertical coordinates and Cartesian or curvilinear, orthogonal horizontal coordinates to represent the physical characteristics of a waterbody. It solves three-dimensional, vertically hydrostatic, free surface, turbulent averaged equations of motion for a variable-density fluid. Dynamically-coupled transport equations for turbulent kinetic energy, turbulent length scale, salinity and temperature are also solved. The EFDC model allows for drying and wetting in shallow areas by a mass conservation scheme. The physics of the EFDC model and many aspects of the computational scheme are equivalent to the widely used Blumberg-Mellor model and U. S. Army Corps of Engineers'Chesapeake Bay model. EFDC's role in the TMDL Toolbox will be to provide necessary hydrodynamic inputs to WASP, the advanced receiving water quality model.

EFDC Preprocessor

In order to facilitate the setup and application of EFDC, a preprocessor is being developed. The preprocessor will be composed of two major components: the Curvilinear Grid Generator and the EFDC Model Interface. Together these components will enable users to generate curvilinear-orthogonal grids, simulate aquatic systems in 1, 2, or 3-dimensions, link 2-D grids to 1-D grids, quickly and easily set and change critical modeling parameters, and make use of watershed loading model results and monitoring data for boundary conditions.

The Curvilinear Grid Generator will enable a user to generate curvilinear-orthogonal grids that are required for the numerical model. It will significantly decrease the repetitive effort typically required through manual grid generation methods. Grid generation will be conducted interactively and intuitively through the interface and associated controls. Key features of the tool will include:

  • GIS interface
  • Model domain designation through user control point designation
  • Automatic insertion of grid boundary points based on control point designation
  • Automatic curvilinear-orthogonal grid generation
  • Model grid conversion to GIS shape file format
  • Cell mapping between EFDC and WASP

Once a grid has been generated, it's necessary to set and calibrate pertinent modeling parameters. The EFDC interface will simplify the setup and application of EFDC through a user-friendly graphical interface and associated windows. It will support input of EFDC model run control and model parameter designation, and it will link directly to boundary condition/source data, e.g. watershed model output and point source contributions. Key features of the tool will include:

  • Database-oriented interface
  • Visual linkage to the model grid
  • Visual linkage to point and nonpoint source inputs
  • New model parameter addition and accommodation
  • Direct linkage to WRDB for boundary condition designation/generation
EFDC Model Information
Current Version
Release Date
July 9, 2002
Operating System
Windows 95/98/ME/2000/XP
Intended Audience
Environmental Engineers/Scientists, Regulatory Agencies
Key Words
hydrodynamics, temperature, salinity, stratification NPS related, NPDES, point source(s), surface water, test/analysis, TMDL related
Lakes, Rivers, Estuaries
Pollutant Types
hydrodynamic transport, links with Water Quality Analysis Simulation Program (WASP7)
File Type/Priority Filename/Format/Size File Description

EFDC-HYDRO.EXE (EXE) -- Self Extracting Zip File

1 MB

This file contains the EFDC hydrodynamic model. Does not include the EFDC water quality components. Includes a 3-D example of rectangular cross section river. User is encouraged to download model documentation.

EFDC Manual --
Zip File


This file contains the EFDC-Hydro Manual PDF in zip format.

EFDC Fact Sheet (PDF) -- (2 pp., 764KB, about PDF)

This file contains a Fact Sheet about the EFDC Modeling System in PDF Format.
File Download Information


Technical Support Center fact sheet (PDF) (2 pp., 733 KB, about PDF)

TMDL fact sheet (PDF) (2 pp., 697 KB, about PDF)

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