Simulating lake restoration: Benefits and challenges of applying lake ecosystem models

Restoration of shallow lakes are undertaken worldwide to restore the deteriorating impacts of among others eutrophication, but lake restoration projects frequently fail due to complex, lake-specific problems. By incorporating lake-specific characteristics, process-based lake ecosystem models can reproduce several levels of lake ecosystem dynamics during and after restoration measures, and thereby explore potential restoration strategies and guide lake management and policy actions. In this presentation, we illustrate the benefits and challenges of applying complex, lake ecosystem models in a management and restoration context with a focus on shallow lakes that have undergone external or internal restoration. The lake ecosystem models were set-up, calibrated and validated on a +10 years comprehensive dataset covering temperature, nutrients and plankton dynamics from Danish lakes. To support management of catchment areas, scenario simulations with lake models can estimate nutrient loading thresholds for when a specific lake will achieve good ecological condition. Furthermore, lake ecosystem models can simulate a range of restoration strategies and methods (e.g. fish harvest and oxygenation of hypolimnion) to explore and assess impact of measures for a specific lake. Challenges remain when trying to simulate frequent shifts between turbid and clear water states. A model-ensemble approach may to some extent address this. To conclude, lake ecosystem models can serve as a powerful support tool for lake managers and water authorities in guiding restoration strategies and protection policies.