A Multi-Dimensional, Water Quality Model for Surface Water

U.S. Army Corps of Engineers | Engineer Research and Development Center | Environmental Laboratory | Search EL

The CE-QUAL-ICM water quality model was initially developed as one component of a model package employed to study eutrophication processes in Chesapeake Bay. Subsequent to employment in the Bay study, the model code was generalized and minor corrections and improvements were installed.

ICM stands for "integrated compartment model," which is analogous to the finite volume numerical method. The model computes constituent concentrations resulting from transport and transformations in well-mixed cells that can be arranged in arbitrary one-, two-, or three-dimensional configurations. Thus, the model employs an unstructured grid system.

The model computes and reports concentrations, mass transport, kinetics transformations, and mass balances. Features to aid debugging include the ability to activate or deactivate model features, diagnostic output, and volumetric and mass balances. Computations can be restarted following interruption due to computer failure or similar circumstances. CE-QUAL-ICM is coded in ANSI Standard FORTRAN F77. The model operates on a variety of platforms including 486 PC, Silicon Graphics, and Hewlett Packard workstations. A multi-processor version is available but not generally released. The user must provide processors that prepare input files and process output for presentation.

The model does not compute hydrodynamics. Flows, diffusion coefficients, and volumes must be specified externally and read into the model. For simple configurations, flows may be entered through an ASCII input file. For more advanced applications, hydrodynamics are usually obtained from a hydrodynamics model such as the CH3D-WES model. The unstructured, finite volume structure of the model was selected to facilitate linkage to a variety of hydrodynamic models.

There are two distinctly different development pathways to ICM: a eutrophication model (ICM), and an organic chemical model (ICM/TOXI). The release version of the eutrophication model computes 22 state variables including physical properties; multiple forms of algae, carbon, nitrogen, phosphorus, and silica; and dissolved oxygen. Recently, two size classes of zooplankton, two benthos compartments (deposit feeders and filter feeders), submerged aquatic vegetation (roots and shoots biomass), epiphytes, and benthic algae were added, although this version of the code is not generally released to the public. Each state variable may be individually activated or deactivated. One significant feature of ICM, eutrophication version, is a diagenetic sediment sub-model. The sub-model interactively predicts sediment-water oxygen and nutrient fluxes. Alternatively, these fluxes may be specified based on observations. The eutrophication model has been applied to a variety of sites, including:

The ICM/TOXI model resulted from incorporating the toxic chemical routines from EPA's WASP (Water Analysis Simulation Program) model into the transport code for ICM, incorporating a more detailed benthic sediment model, and enhancing linkages to sediment transport models. ICM/TOXI includes: physical processes such as sorption to DOC and three solid classes, volatilization, and sedimentation; and chemical processes such as ionization, hydrolysis, photolysis, oxidation, and biodegradation. ICM/TOXI can simulate temperature, salinity, three solids classes, and three chemicals (total chemical for organic chemicals and trace metals). Each species can exist in five phases (water, DOC-sorbed, and sorbed to three solids types) via local equilibrium partitioning. WASP toxic chemical model upon which ICM/TOXI is based, has been applied to a wide variety of sites. ICM/TOXI will be released when the documentation/user guide report is published.

Point of Contact for ICM:
Dr. Carl F. Cerco
U.S. Army Engineer Research and Development Center, Waterways Experiment Station, Environmental Laboratory
3909 Halls Ferry Rd
Vicksburg, MS 39180

Point of Contact for ICM/TOXI:
Dr. Mark S. Dortch
U.S. Army Engineer Research and Development Center, Waterways Experiment Station, Environmental Laboratory
3909 Halls Ferry Rd
Vicksburg, MS 39180

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