Application of a shallow water model to analyze environmental effects in the Amazon Estuary Region: a case study of the Guajará Bay (Pará – Brazil)

This study used hydrodynamic modeling to investigate the hydrodynamic circulation and pollutant transport of the Guajará Bay-PA. The hydrodynamic modeling was performed using the classical Saint-Venant model for shallow waters. The pollutant dispersion was described using a Lagrangian deterministic model that simulates advective–diffusive transport with kinetic reactions for two-dimensional flow. The finites elements method was used to solve the Saint-Venant and transport equations. The bathymetry data were obtained by combining the data from nautical charts provided by the Directorate of Hydrography and Navigation of the Brazilian Navy. The substrate grain size data for the determination of rugosity were obtained from literature. Data on the tides, the wind and the flowrate of the rivers that form the Guajará bay were used as the boundary conditions in the simulation of the hydrodynamic circulation and the pollutant dispersion scenarios. Flood and ebb tide patterns were simulated, which enabled the contaminant plumes of the Guajará Bay to be simulated. An analysis of the simulated fecal coliform plumes indicated that these pollutants that are produced in the metropolitan region of Belém flow towards the beaches in the North, especially those in the Icoaraci and Outeiro districts, affecting the bathing water quality.