Incthe present study, carried out on the Hammam Boughrara dam (impounded in 1999), a number of phosphorus balance models were applied, namely, Vollenweider (1969), Dillon and Rigler (1975), Walker (1977), Reckhow (1977) and Ostrofsky (1978) models. In order to take into account, the rate of gradual submergence of flooded surfaces which is ordinarily characterized by an important increase in the trophic status as a result of endogenous inputs of phosphorus by leaching we have tried to adapt the Ostrofsky model (1978) to the reality of studied dam, by adding a new dimension. The obtained results show that the proposed model seems relevant.