USE AND MISUSE OF COMPLEX MODELS: EXAMPLES FROM WATER DEMAND MANAGEMENT¹

Abstract

The power of computers has increased in recent decades, and one might expect improved management to result because decisions can be made with understanding available only via models. However, there is potential for quite the opposite: poor decisions due to unrealistic model output generated by users without access to appropriate training in the use of models. We discuss and, by reference to water demand models (IWR-MAIN, MWD-MAIN), illustrate three areas in which unintended errors of judgment by untrained personnel may cause difficulty:• Attributes of management models; if output from any type of model has no measure of confidence, then results may be over-or undervalued • Input data; with complex models, problems here typically will be difficult to detect.• Calibration and history-matching (verification); if these steps or data are combined, then users should be less trustful of model output than otherwise.Because all models have weaknesses and because there always is uncertainty about output from any model, we end with suggestions for coping with complex models. Monitoring programs play a central role in such efforts because they can identify discrepancies between model predictions and actual events and because they can ensure time is available to develop solutions for problems unanticipated in the modeling effort. (KEY TERMS: models; modeling; IWR-MAIN; MWD-MAIN; water forecasting systems; water use; water demand.) IPaper No. 94016 of the Waler Resources Bulletin. Discussions are open until December 1, 1995. 2Respectively, Associate Professor,

Developing decision support systems for integrated coastal management in the tropics: Is the ICM decision-making environment too complex for the development of a useable and useful DSS?

“…Comprehensiveness and complexity do not necessarily lead to increased accuracy (Loucks, 1987). However, Parker et al (1995) warns against taking extreme positions on the use of models emphasising that while they may not provide all the answers, they are also not a waste of time. He continues to point out that model results and predictions should be accompanied with some indication of the level of confidence that can be placed on the outcome, avoiding the results being either under or over-valued, or discounted entirely.…”

“…While the name 'decision support system' suggests a system capable of improving decision-making, there is a danger that misapplication of models and tools can lead to unrealistic and misleading outputs (Parker et al, 1995). Much of this can be overcome through careful design of the system and ensuring the appropriate information is given to the decision-makers about the model and its limitations with system checks to avoid misuse.…”

“…The use of computerised modelling techniques as management tools has increased as computers have become more user-friendly and accessible (Parker et al, 1995). The development of these computerised decisionsupport tools in coastal management is increasing, and being led by some of the major international organisations.…”

JAWRA: Fifty‐Five Years of Sustained Contributions for Improved Water Resources Management — The Fourth Decade (1995–2004)

“…The improvements in user interfaces, and the ability to take modeling to the masses, were seen as fundamental breakthroughs for collaborative water resources planning and management (e.g., Simonovic and Bender ). However, Parker et al () illustrated that poor decisions could arise when people without significant training performed modeling. They identified three major areas of concern: (1) lack of measures of confidence often result in over‐ or under‐valuation of model results; (2) errors in input data become hard to detect especially as the complexity of the model increases; and (3) mixing of data used for calibration and verification steps can reduce the confidence in the model predictions.…”

Evaluation de la fiabilité de gestion d'un barrage réservoir pour des événements secs / Assessment of the reliability of reservoir dam operation for dry events

“…Mais, malgré le développement de la technologie informatique et la possibilité d'appliquer des procédures mathématiques plus complexes aux analyses de fonctionnement des réservoirs, la planification et la gestion quotidienne des systèmes de réservoirs ne bénéficient pas forcément des méthodes les plus originales d'analyse et de simulation des systèmes, ni des optimisations les plus efficientes. A cet égard, plusieurs chercheurs dans le domaine de la gestion des ressources en eau (Rogers & Fiering, 1986;Loucks, 1992;Parker et al, 1995) ont remarqué que l'application pratique des méthodes d'analyses des systèmes nécessite des modèles plus transparents et moins complexes. Ceci devrait permettre aux utilisateurs finaux de mieux comprendre les modèles et, par conséquent, de les utiliser d'une manière plus efficiente et bénéfique.…”