ERM Surfacewater Modeling Group - GEMSS<sup>®</sup>

Generalized Environmental Modeling System for Surfacewaters (GEMSS^®)

The Surfacewater Modeling Group has encapsulated many of its analysis techniques in the software system GEMSS^® (Generalized Environmental Modeling System for Surfacewaters). At the heart of the system are four hydrodynamic modules: the 3-D model GLLVHT (z-grid and sigma-grid), the 2-D longitudinal-vertical model CE-QUAL-W2, the 1-D model GLHT, and the 0-D (fully-mixed) model RTC.

In addition, GEMSS^® includes the following constituent modules:

Water Quality Module - WQM
Sediment Transport Module - STM
Toxics Module - TOX
Particle Tracking Module - PTM
Chemical and Oil Spill Impact Module - COSIM
Thermal Analysis Module - TAM
Generalized Bacterial Module - GBM
Generalized Algal Module - GAM
Entrainment Module - ENM

GEMSS^® includes a graphical user interface that supports these modules and provides additional capabilities, including:

Grid generation
GIS compatibility
Field databases with analysis and visualization
Boundary condition data pre-processors
Post-processors for model output graphing and statistics
3-D animator

Also operating under the GEMSS^® GUI are the freely available, peer-reviewed community models such as CE-QUAL-W2, the Princeton Ocean Model (POM), the Estuarine and Coastal Model Sediments (ECOMSED) and the Environmental Fluids Dynamic Code (EFDC). These models can be run separately using the GEMSS^® GUI for comparison analysis. The core of these models is unchanged under GEMSS^® to preserve their strength of wide acceptability in the modeling community.

GEMSS^® has had extensive application experience and has been accepted by many U.S. regulatory agencies including the EPA, the Bureau of Reclamation, and state agencies such as NJDEP, DNREC, WADOE and others. Outside the U.S., GEMSS^® have been approved by the World Bank, Qatar, and the Bahamas, among others.

Fundamental in our approach to working with our colleagues is the offer to share GEMSS^®.

Distribution
To understand our distribution policy, it is necessary to understand the history of GEMSS^® and some facts about its status.

The initial component of GEMSS^®, the hydrodynamic kernel GLLVHT, was written in 1980 by John Edinger and Edward M. Buchak, using the finite difference forms and solution technique they developed for CE-QUAL-W2. Beginning in 1994, Venkat Kolluru added many new constituent calculations, improved the basic solution techniques, added a number of tools, and designed the graphical user interface. Our development methodology has always been to extend the computations when required for new applications. These extensions were occasionally funded by clients, but more often funded internally or through donated staff time.

GEMSS^® is first and foremost a model we use day-to-day - built to work on surfacewater problems the way we approach them. Although it is an excellent productivity tool, GEMSS^® is a "work in progress" and does not have the level of perfection of mass-market software packages.

In general, we provide GEMSS^® at no charge to qualified users. However, we need to limit our liability and strongly urge you to avail yourself of our technical support services, attend a training workshop, and allow us to set up your first application.

The distribution policy accomplishes the following

limits our liability
ensures that your unfamiliarity with the software doesn’t inadvertently result in a loss of credibility for us or for GEMSS^®
obtains feedback from you on your use of GEMSS^®
gives you the opportunity to take a training workshop and to have access to various levels of technical support
requires that you credit our work in reports and papers
ensures that your commercial activities with GEMSS^® don’t interfere with our need to be fairly compensated for our efforts and expertise.

When you request a copy of GEMSS^®, we will first ask about you, your organization, and the waterbody and problem you wish to solve. If we choose to send you the executable, you will first be required to acknowledge an agreement covering the issues summarized above.

Obtaining a Copy of GEMSS^®
Send your e-mail request to Venkat S. Kolluru (venkat.kolluru@erm.com) or Michael J. Fichera (michael.fichera@erm.com ).