GIS Based Chemical Fate Modeling: Principles and Applications

Chapter 15

Complex Models, GIS, and Data Assimilation

Although GIS enables tackling several chemical fate and transport problems with simple calculations, there are still many other problems that require complex or very complex models. This is particularly true when advection does not follow a simple and constant pattern, such as the topographic surface—as for the stream network—but the gradients of other potential surfaces. Typical cases include atmospheric transport, transport in groundwater, and two- or three-dimensional transport in surface water including oceans. In the case of surface water, to the best of our knowledge no method exists that simplifies the calculation of flow fields for subsequent use in chemical transport models, and numerical solutions of the flow equations required for simulating contaminant transport need to be obtained from standard numerical codes requiring specific numerical modeling skills. For the atmosphere and groundwater, however, tools exist that enable simulations and do not require such skills. In the case of the atmosphere, available tools that couple complex models with a simple user interface and robust settings enable even nonspecialists to access chemical transport and air trajectory simulations. For groundwater, the analytic element method (AEM) enables simulating complex flow fields through superposition of analytical solutions. Although the method requires in-depth understanding of groundwater flow mechanics, the implementation of AEM ...