An integrated approach for urban water modelling, linking a watershed hydrological model and a cyanobacteria dynamics model in urban lakes

In the future, the frequency and the intensity of cyanobacteria blooms in urban lakes are expected to increase in response to climate change and expanding urbanization. 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 hydrological watershed model, is proposed. To validate this approach, the water quality (temperature, transparency, dissolved oxygen and chlorophyll-a) was monitored at high frequency (5-30 min) on two study sites in contrasted regions (climate, land-use...). In the first part of this paper, we show the advantage of using high-frequency data to simulate cyanobacteria dynamics in Lake Enghien (France), a temperate urban lake. In a second part, the methodology used, to link the ecological lake model and the hydrological watershed model is explained for Lake Pampulha (Brazil), a tropical urban lake. Some preliminary results of the ecological modelling of Lake Pampulha are also presented. The integrated modelling approach proposed, will allow us to study the lake response to different future scenarios of the watershed evolution. Furthermore, high-frequency data are expected to provide a better understanding of the lake functioning during extreme meteorological conditions (e.g. heavy rainfall events or drought).