Simple mass balance model for aquaculture area, based on the Vollenweider equation:

dMw/dt = Min - sMw - Mout

The model was first used in the 1960s to determine the phosphorus concentration in lakes and reservoirs for eutrophication assessment.

Direct loading replaces input concentration

The key uncertainty in these models is s, the loss of phosphorus to the sediment. Calculation of s, and the retention coefficient R used in the Dillon & Rigler model, was extensively analysed on the basis of existing literature, and the final equation used was from Canfield & Bachmann, 1981, for natural lakes.