Multiobjective decision-making in integrated water management

Traditionally, decision-making by water authorities in the Netherlands is largely based on intuition. Their tasks were, after all, relatively few and straight-forward. The growing number of tasks, together with the new integrated approach on water management issues, however, induces water authorities to rationalise their decision process. In order to choose the most effective water management measures, the external effects of these measures need to be taken into account. Therefore, methods have been developed to incorporate these effects in the decision-making phase. Using analytical evaluation methods, the effects of various measures on the water system (physical and chemical quality, ecology and quantity) can be taken into consideration. In this manner a more cognitive way of choosing between alternative measures can be obtained. This paper describes an application of such a decision method on a river basin scale. Main topics, in this paper, are the extent to which uncertainties (in technical information and deficiencies in the techniques applied) limit the usefulness of these methods, and also the question whether these techniques can really be used to select measures that give maximum environmental benefit for minimum cost. It is shown that the influence of these restrictions on the validity of the outcome of the decision methods can be profound. Using these results, improvement of the methods can be realised.