Theoretical model for the water quality model of a lake "Lerne"

"Lerne" is an eutrophication - dissolved oxygen model which can be a powerful tool for assessing the water quality characteristics of a lake in relation with its water uses. The model involves the mathematical expression of all physical, biological and chemical processes which are taking place in the water column and are crucial for the fate of the pollutants, like advection, diffusion, phytoplankton growth, nutrients consumption, nitrification, denitrification and physical reaeration. The parameters being modeled are phytoplankton, nitrogen, phosphorus, organic carbon and dissolved oxygen. In case of a stratified lake the model allows for the prediction of the concentrations in the top and the bottom layer. Finally in order to account for the random fluctuations in the kinetic constants and the model's input data, the model incorporates a stochastic approach technique which produces a set of possible values for each substance examined. This report is the scientific documentation of the model "Lerne".