Dilllon-Rigler Model is an empirical model that predicts average summer chlorophyll-a concentrations in temperate lakes from total phosphorus concentrations at spring overturn (phosphorus concentrations are near-constant from surface to bottom during spring mixing). In general, average summer chlorophyll-a concentrations in temperate lakes increases with increasing spring overturn phosphorus concentration. The model has been well documented and widely used by lake managers, limnologists and researchers to set phosphorus loading guidelines for lakes and to set lake restoration objectives.