Environmental Engineering Reference
In-Depth Information
be - there will always be additional influences that have to be ignored and cannot be
integrated in a given context. A
complete
model of ecological interactions in any
field is impossible. Therefore, delimitations (where to end the list of relevant
influences) require good reasoning and judicious decisions of the modeller. Regard-
less of how well the rest of the work is done, unreasonable decisions about what to
consider and what not, can determine the usefulness of the entire work. Therefore,
this issue should be taken very seriously. Decisions require a balance and linkage of
the general nature of the problem under consideration, as well as the specific
working conditions and available technical, logistical and intellectual means.
Models Need Intelligently Chosen Criteria for the Distinction
of Important and Unimportant Aspects
There has to be a consideration of relevance concerning elements and relations that
could make an important part of a model. The decision about which subjects and
interactions are considered to be relevant depends on the available background
information. During the work, it may turn out that the background information was
not sufficient. A careful analysis of what is already known in the field is crucial. The
modeller needs a clear view of which influences contribute (sometimes, always or
only under specific conditions) in an important way to the given problem. There-
fore, a literature survey to attain an overview that goes well beyond the current
focus is required. Often the necessary decisions should be prepared in a discussion
with co-operators or other experts in the field and experts in related topics.
Furthermore, a consideration of the working conditions for the modelling pro-
cess is required: What is the available time span, what are the resources, manpower,
data bases, etc., and what are the temporal constraints of model development? The
answers can be integrated into a synopsis of the requirements to solve a given
problem and the compromises that derive from the limitations (and preferences) of
the specific situation. This background knowledge will allow the modeller to
develop a reasonable work plan. Experience tells us that the duration (time require-
ment) of model elaboration is difficult to anticipate. Certain steps may be achieved
much more easily and faster than expected; however, in most cases unexpected
obstacles occur and things usually take longer than expected.
2.3 The Modelling Potential: What Can Models Help to Do?
Models are used for a wide range of purposes. Wainwright and Mulligan (2004) list
different application fields for environmental models. They can, for example, be
applied as an aid in research, as tools for understanding, tools for simulation and
prediction, as virtual laboratories, and integrators between disciplines, and in
