M. Dahl and D.I. Wilson
Lake modelling, validation, eutrophication, initial conditions, Leeds
Lake models have the potential to assist decision-making authorities regarding issues in environmental planning. However, validating ecosystem models over relatively short time spans can lead to deceptively good results, especially if the initial conditions of poorly known states are themselves regressed. This is most noticeable when the ecosystem is not in a steady periodic cycle, such as is the case with large lakes. These problems are illustrated using a water-quality lake model for Lake V¨anern in Sweden compared with over a century of validation data. This paper shows that it is possible to construct a convincing, but erroneous, 30-year simulation at the expense of exhausting the accumulated phosphorus in the sediment. To address this problem, it is necessary to use validation data collected over much longer time spans, such as 100 years. Consequently, this work highlights the extensive data collection requirements for the adequate validation of freshwater ecosystems.
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