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Wageningen University (1999)

The role of eutrophication models in water management

Molen, D. van der

Titre : The role of eutrophication models in water management

Auteur : Molen, D. van der

Université de soutenance : Wageningen University

Grade : PhD thesis 1999

Résumé partiel
In this thesis the role of eutrophication models in water management is analysed. The thesis consists of an extended introduction followed by five Appendices with papers describing different mathematical models dealing with eutrophication in surface waters. At first systems analysis is described as a general framework for eutrophication modelling. Emphasis is put on the uncertainties inherent in predictions. Next, a set of criteria is derived from this. The criteria may be useful in evaluating previous work and in guiding new initiatives on eutrophication modelling. Accordingly, the criteria are applied to review studies described in three of the five papers and to evaluate a number of projects of different lake managers in The Netherlands.

Systems analysis, an approach to solve problems, is utilised as the framework to study problems related to eutrophication of surface waters. The following stages are distinguished in this approach : problem analysis and the formulation of objectives, the set up of a conceptual framework, analysis of available data, specification of the mathematical formulations, sensitivity analysis, parameter estimation, validation and finally application of the model. Application of this approach generally results in repeatedly going through several stages, so systems analysis is a cyclic rather than a one-way procedure. Several examples from the field of eutrophication illustrate the approach.

Contrary to common practice of systems analysis the proper technical development and/or application of the model, referred to as _credibility_, is explicitly distinguished in this thesis from the acceptance of the results, referred to as _acceptability_. This is in agreement with actual pratice in water management, where the modeller, the user of the model and the user of the results of the model often are two or even more different persons. Credibility and acceptability are thus specified in a set of criteria which may be useful for both modellers and users of the model (results). The criteria addressing credibility are : the objectives of the model and the ensuing choice of the state variables, the dimensions of the modelled system and aggregations in time and space, the utilisation of the available data, the appropriateness of the model structure, the determination of parameter values, the validation of the model and finally the assessment of the uncertainties in the structure, the parameters and the results of the model. Criteria addressing acceptability are : attention to the motivation to undertake a modelling project, specification of the constraints in time and money, explication of the arguments to accept or reject (parts of) the model (results) and consideration of the consequences of the use of the model (results).

Mots clés : hydrology / water management / eutrophication / simulation models / models / research

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Page publiée le 9 janvier 2015, mise à jour le 17 décembre 2021