Improving the relevance and impact of water quality modelling for decision-making

Abstract: Catchment managers often turn to computer-based water quality models to support catchment and natural resource management (CNRM). However, model use by managers is inherently problematic. Often-reported problems include inadequate or poor quality input data, miscommunication between scientists and managers, inappropriate treatment of model uncertainty and excessive model complexity or simplicity. This paper reports on the methodological lessons learned from several CNRM projects in New South Wales, Australia. Six modelling project management problems that significantly impact on the utility of models in decision-making are discussed: 1. Relevance and impact. Model evaluation usually focuses on the technical quality of models. Relevance to the decision-making problem and impact on the decision that is made are more useful indicators of model effectiveness in decision-support. 2. Methodological tension. Disparate thinking amongst practitioners within knowledge communities can inhibit effective model use as much or more than disagreement or misunderstanding between scientists and managers. 3. Model uncertainty. Most treatments of uncertainty focus on quantifiable uncertainties and their assessment using sensitivity and uncertainty analyses. Conceptual uncertainties, which are difficult o