Modelling cyanobacteria dynamics in urban lakes: an integrated approach including watershed hydrologic modelling and high frequency data collection

Urban lakes performed several essential functions for the cities such as storing rainwater and providing recreation spaces. Blooms of cyanobacteria frequently occur in these lakes, disrupting water uses and decreasing ecosystem biodiversity. In order to study the impacts of watershed changes on cyanobacteria dynamics in urban lakes, a modelling approach in which an ecological lake model is connected to a hydrologic watershed model is proposed. To validate this approach, two study sites were selected: Lake Enghien (France) and Lake Pampulha (Brazil). In the first part of the paper, we assess the performance of a lake ecological model fed with high-frequency data collected in Lake Enghien. In the second part, we propose a methodology to connect the lake ecological model to a watershed hydrological model using data set from Lake Pampulha. Our results on cyanobacteria modelling in Lake Enghien (correlation coefficient = 0.71-0.97; RMSE = 15.8 – 25.7 μg chl-a L) show the reliability of the lake model. In Lake Pampulha, the high-frequency data are expected to provide understanding about poorly known processes in lake functioning. Finally, as future steps of this research, the integrated modelling approach will be used to estimate lake response to different scenarios of the watershed evolution.