Trophic Upsurge in New Reservoirs: A Model for Total Phosphorus Concentrations

Abstract

A model for total phosphorus concentrations during both the trophic upsurge and depression phases in new reservoirs has been developed by a convolution of the rate of phosphorus leaching from flooded lands and the rate of reservoir filling. Model parameters for phosphorus sedimentation and leaching coefficients were estimated from data available on the Smallwood Reservoir (impoundment 1971) in Labrador. The model was subsequently applied to predict phosphorus concentrations during the trophic upsurge phase in the La Grande-2 (LG2) Reservoir (impoundment 1978) in the James Bay region of Quebec. Because the sparse data available on other new or old reservoirs during the trophic upsurge phase does not permit an analysis of the confidence limits in model output, we include discussion of the calculated values of model parameters and their relationship to the real phenomena. An evaluation of the rates of phosphorus leaching from flooded soils and vegetation and the specific leaching coefficient of phosphorus from various lands has shown indirectly that the proposed model approximates the dynamics of new reservoir phosphorus concentrations. We conclude that the model has a good potential as an empirical predictive tool in the management of large new reservoirs on the Canadian Shield.Key words: reservoir, phosphorus, model, trophic state