5.1.5 Modelling procedure

Modelling procedure has to be carried out in a systematic way to get an optimum allocation of limited resources to relevant activities. The primary focus is to define the problem, bound by the constituents of space, time, and subsystems. Once the problem is defined, a suitable model has to be selected or developed to fit the situation. Before this decision can be made, a thorough study of the available data, resources, and an assessment of the required level of detail should be conducted. This will help to choose the correct model, whether simple or complex.

Calibration should be carried out after analysing the data. This can be done by reconciliation of the values predicted by the model and the actual observed values. Various curve fitting and optimization methods can be used to aid the calibration procedure.

After the calibration is carried out, it is important to validate the model, preferably against a series of measures from a period with changed conditions. For this second step, a set of available data can be used. If significant discrepancies exist, the general model formulation should be reviewed and the calibration and validation cycle repeated.

After the calibration, the model is ready for application. First, the model is applied to the existing conditions without the project. Next, proposed project parameters are added and the model is run again to predict the quality of environment after the establishment of the project. The difference between the two predictions comprises the environmental impact of the proposed project.

Sensitivity analysis is the integral and important component of the entire model study. This enables the modeller to evaluate the relative importance of the basic parameters and input data in the model study.