Page 198 - Soil and water contamination, 2nd edition

Systems and models 185

Figure 10.3 Propagation of spatial and temporal variation in groundwater.

that it emphasises relationships between driving processes and resulting patterns. This makes
it possible to link observed patterns of contaminants in soil and water to the most important
processes causing the patterns.

10.2 THE ROLE OF MATHEMATICAL MODELS
In the past thirty years, the increased availability of computing power has led to hydrological,
hydrochemical, and ecological computer models becoming widely used for managing
soil and water quality with respect to a variety of environmental impacts. Mathematical
models that simulate the transport of contaminating substances allow us to evaluate the fate
and persistence of these substances in landscape compartments in space and time and to
accurately predict the physical, chemical, and biological processes occurring during transport.
The main output from these models is the chemical concentration of one or more chemical
substances as a function of space or time, or both. The principles of mathematical modelling
of solute and particle transport are based on those of systems theory .
We build and apply such environmental models of contaminant transport for the
following reasons:
1. To forecast travel time s of pollutants in rivers or groundwater when calamities occur.
2. To assess past, present, or future human exposure to contaminants.
3. To predict future conditions under various scenarios of environmental change and
management strategies and to evaluate the effectiveness of possible management actions.
4. To reduce soil and water quality monitoring costs by replacing or supplementing
expensive measurements by cheaper model predictions.

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