The modeling software you select for your project depends on project objectives, budget, schedule, and available programming resources.  A general set of modeling software selection guidelines is available from this Engineering Practices document by the American Society of Agricultural and Biological Engineers. However, in terms of hydrodynamic and water quality simulation software, there are some specific features to look out for, as well as unique aspects of modeling that we recommend users consider when choosing software tools, as outlined in this blog.

In our previous blog, we looked at different available versions of EFDC. If you intend to use a version of EFDC or similar core computational tools, here are a few things to think about:

• END-USE: It is essential to consider the end-user when choosing an EFDC version. Developing a tool for frequent use by a regulator will have a different set of requirements than one built by an expert for use by that expert.  Suppose the model is to be used by more than the original developer. In that case, it is vital to have a user interface to facilitate updating model inputs and analyzing the model results. Tools are available for post-processing with R, such as EFDCR. However, this doesn’t help with building the model. If you are developing a model for your personal use, you will need to determine the level of effort required to maintain and use the model.
• OBJECTIVES: During the model selection process, it is essential to match the computational tool, i.e., model, to the project requirements.  The basic hydrodynamics are available for all versions of EFDC, though there are differences in available sub-options and model performance.
• BUDGET: If your budget is limited and you have programmers who can customize the code for your specific project, one of the open-source options may suffice. Remember that technical support for these models is mainly community-based—that is, your personal network of experts and any online forums you can find.  DSI currently hosts one of the most active EFDC communities on the web.
• SCHEDULE: If you are building a new model, working directly with any EFDC version of the code without a user interface can take many months to years. Utilizing a software tool like EFDC_Explorer to provide a GUI and pre-and post-processing can dramatically speed up modeling efforts. 
• MODEL RUN TIME: To best represent the processes in your waterbody, it is always a good idea to dedicate time to the calibration process. This process inevitably involves multiple runs as you tweak parameters and adjust the model configuration. This can be quite a fast process in small, simple domains, and shorter periods can be simulated. However, run times can take several days in larger systems, and in cases where multiple modules are activated. Selecting software tools that use parallel processing is helpful in these cases. EFDC+ uses the OpenMP and MPI technology to utilize one or all of the processors on your modeling workstation.  This can result in reduced model run times by a factor of four or more.
• DENSITY STRATIFICATION: If you are working on a stratified water body such as an estuary, lake, or harbor with abrupt changes in the bed, the standard EFDC vertical gridding system (Sigma stretch) may cause unrealistic vertical mixing of the water.  Your model may suffer from a well-known “horizontal pressure gradient error” problem (Mellor, et.al., 1994). With the addition of the Sigma-Zed sub-module in EFDC+, you can significantly reduce the horizontal pressure gradient error and better represent the vertical density structure of your system in the model.
• HYDRAULIC STRUCTURES: If you need an EFDC solution that involves modeling different hydraulic structures such as sluice gates, orifices, or weirs, EFDC+ provides the option of efficiently representing such hydraulic structures anywhere in the model domain.
• LAGRANGIAN PARTICLE TRACKING AND OIL SPILL:  If you are working on a system to model oil spill tracks, emergency response, water quality applications, and plume tracking, EFDC+ provides many options with its robust Lagrangian particle tracking
• MULTIPLE DYE CLASSES: Developing a full WQ model is time-consuming, so users often find it more convenient to use dye as a proxy for a WQ constituent. Dye can be simulated as a conservative or non-conservative constituent in most versions of EFDC. In contrast to other versions, EFDC+ allows the user to configure any number of dye classes into the simulation to develop more complex scenarios.
• EUTROPHICATION & BIOTA: Many models can simulate eutrophication. EFDC simulates up to three phytoplankton types (cyanobacteria, diatoms and green algae) and one macroalgae group. It also includes a full sediment diagenesis model to simulate nutrient cycling among the biota and sediment bed. In the natural world, however, multiple dominant species of algae, plants, and animals (e.g., zooplankton) may be present in a waterbody and require detailed modeling. EFDC+ includes a generic formulation for “macrophytes and algae” groups and zooplankton groups. This gives the flexibility to model unlimited algal species and consider the role of zooplankton both as grazers that control algal population and as a food source for higher trophic-level organisms in a waterbody.
• ICE MODELING: Are you working on colder regions where ice formation and ice melt impact the hydrodynamics, surface processes such as oxygen reaeration, or contaminant fate and transport? EFDC+ gives an option to represent the ice formation/melting with a robust ice submodule link to the heat sub-model.  Heat is conserved in the ice formation and melt process.
• EFDC CUSTOMIZATION:  Many companies have expertise in EFDC. They can help you build your model and develop new capabilities in the code. At DSI, our team loves to work with our clients to help them better understand their system and achieve their goals. If you need advanced features, a dedicated support team, or do not have the time or resources to build your own custom solution, EFDC+ is a good option.
• SUPPORT: The long-term success of EFDC and your EFDC project may depend on continued code development and bug fixes, as well as project support.  DSI manages and responds to the EFDC forums as well as for EFDC_Explorer. We will soon make the full MPI version of EFDC+ for EEMS10.4 available on Github to allow for a more collaborative development approach.