Integrated Modelling of Lake Pampulha: Assessing the Catchment Impact on Cyanobacteria Dynamics in the Lake

Abstract : Among the many pollutants loaded by the urban runoff, nitrogen and phosphorus are of particular concern for lakes which are especially vulnerable to nutrient enrichment because of the high water retention time. Eutrophic lakes are frequently affected by cyanobacteria blooms, including toxic species, which can be harmful to human health. To provide a tool for studying the impacts of catchment changes on the cyanobacteria dynamics in urban lakes, a modelling approach in which a hydrological model is connected to an ecological lake model is proposed and applied for Lake Pampulha, Brazil. The lake and its catchment were intensively monitored from October 2011 to June 2013. The hydrological model SWMM was used to simulate runoff volume and TSS, NO3, NH4 and P total . SWMM results were input into the lake ecological model DYRESM-CAEDYM, which was used to simulate cyanobacteria dynamics. The hydrological model showed a good performance for runoff simulation (Nash criterion between 0.70 and 0.88) and poor results for nutrient simulation. The lake model showed good predictive ability of the cyanobacteria dynamics (NMAE between 0.26 and 0.55). Results of the model and a sensibility analysis highlighted the link between cyanobacteria dynamics and the urban catchment.