Modelagem simplificada do fósforo total em lagos e reservatórios brasileiros

Abstract

Phosphorus is considered the main factor responsible for eutrophication of lakes and reservoirs. In the present study, a transient complete mixing model was used to analyse phosphorus dynamics in 40 lakes and reservoirs located in the Northeast, Southeast and Central-West regions of Brazil. The results confirmed the dependence of the phosphorus decay coefficient on the inverse of the square root of the hydraulic residence time. However, due to the high-water temperature of the lakes and reservoirs of the Northeast, this coefficient assumed values about two times higher than those observed in regions of tropical climate. On the other hand, due to the high temperature variability of the lakes and reservoirs in the Southeast, the coefficient oscillated between extreme values observed in temperate and semiarid regions. As a result, a general equation was proposed to calculate the phosphorus decay coefficient as a function not only of the hydraulic residence time, but also of the water temperature. After validation and sensitivity analysis of the proposed model, it was applied to a hypothetical reservoir subject to temporal variations of water volume, flow, load and temperature. This simple model will potentially assist in the management of Brazilian lakes and reservoirs.