Model Development and Analysis

The development of a model requires clear agreement on its purpose and context, involving not only the modelers but also the stakeholders in its use. The process of achieving agreement is iterative, with continual refinement of the purpose and objectives as the modelers and stakeholders learn more about the system modeled and the scope for using the model. From that point conceptual models can be developed to guide the choice of model features and families and to help determine how model structure and parameter values are to be found. Performance criteria can then be developed, geared to the model purpose, context and structure, and the available data. Once constructed, the model must be subjected to calibration, quantification of uncertainty, model testing, and evaluation of its effectiveness. At any point it may be necessary to revisit and revise earlier steps as new information unfolds. This article discusses a ten-step model approach in the context of a 3-year project to develop an ecological model for a wetland system. It is hoped that discussing the model development options at an early stage of the project will draw out more of the issues and options.