The expression “use the right tool for the right job in the right way” has traditionally been associated with building, electrical and other trades to make it easier to get a job done effectively and safely. That expressional can apply to selecting and applying mathematical models for environmental forensics or forecasting.  In some cases, regulatory agencies prescribe specific models and scenarios for environmental modeling, but those procedures may not adequately address unique situations or prove to be sufficient.

At Waterborne, selecting the “right tool” involves answering two questions: 1) “What are you trying to accomplish?” and 2) “What are the constraints that may necessitate specialized tools?” The answers to these questions begin with the development of a conceptual model to determine the most important processes that need to be represented in a model while considering constraints of accuracy and precision requirements, data availability, budget, and time.

Many environmental models operate under a steady state and under assumptions of conservation of mass. Truly dynamic models include the simultaneous solution of conservation of mass and momentum, thus allowing non-steady state conditions to be modeled, such as pulse doses, tidal exchanges, and backwater conditions.  Multi-dimensional models can address processes such as:

• How does chemical exposure vary over time and by distance?
• Where are constituents likely to deposit into sediment and how often will they flush out by sediment scour?

Below we illustrate four examples of multi-dimensional modeling.