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Modeling Approaches

A model is a graphical, statistical or mathematical approximation of a real lake or reservoir. Models used for understanding eutrophication focus on nutrient loading from the watershed and on processes within the lake or reservoir. While these models have considerable differences in their complexity, in most situations, simpler approaches are sufficient and are often the only practical option.

Simple empirical regression models have been developed to predict the concentration of total phosphorus in a lake or reservoir as a function of annual phosphorus loading. Extensions of such models offer predictions of chlorophyll concentrations in phytoplankton, Secchi disk visibility or dissolved oxygen levels.

Dynamic simulation models incorporate mathematical descriptions of physical, chemical and biological processes in lakes and reservoirs. If properly designed and validated, these models can assist with management decisions. However, the data requirements and process-level understanding demanded by dynamic models can be formidable.

Evaluation of a model requires careful examination of the assumptions underlying the model and a rigorous analysis of the way the model responds to a range of inputs. It is prudent to be skeptical of their predictive power and realism.

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