The model uses the super-individual approach (Scheffer et al., 1995). Each super-individual represents a number of individuals which all have the same growth rates, individual weight, and height. We simulate each species separately as one super-individual per depth. The model calculates the daily biomass, the height, and the number of sub-individuals for each of these super-individuals (Figure 1b). The MGM considers influences of geographic factors (daylength and water depth) and environmental factors (irradiance at surface, nutrients, water temperature, and turbidity) on the growth of submerged macrophytes. The growth of macrophytes is mainly driven by photosynthesis and respiration. Photosynthesis depends on depth-dependent light, nutrients, and temperature, while respiration depends only on temperature. Furthermore, the processes of self-thinning, depth dependent mortality, plant senescence, and self-shading influence growth.