Aplicação do modelo hidrodinâmico no estuário do rio Caeté (NE do Pará)

Abstract

The northern coast of Brazil is trimmed by a big and complex hydrographic net, where the main river is the Amazon. This river, as well as others smaller, flow into in the Atlantic Ocean finalist the estuaries, that are frequently defined like a stretch of the river, where occurs the interaction of the ocean and fluvial waters (transition zone). The Caeté estuary is inserted at the northeast of Pará (00º43’18" – 00º04’17" S and 46º32’16" – 46º55’11" W) that suffers influence of macro-tides and semi-diurnal with medium amplitude of 5,6 m, coastal currents (mean velocity approximately 0,75 m/s), waves of 0,7 m and Trade winds that possess NE preferential direction with medium speed of 6 m/s. That estuary is situated in a tropical region of humid climate, with annual medium temperature of 27ºC and elevated precipitation with annual medium of 2500 mm/year. In this area, are also showed, the existence of seasons with distinct characteristics: rainy (December to May), dry (June to November) and intermediate. The estuary of the Caeté river is a tide-dominated estuary (as regards the physical process), that forms an extensive coastal plain (as regards the coastal geomorphology) and well mixed (as regards waters circulation).The hydrodynamic circulation in estuary is considered as an important trial and it has a lack of studies in this area until today, principally in the North’s region of Brazil, where still have a few the studies of estuarine modeling. So, for this work were adopted the use of the hydrodynamic model with the Modeling program called SisBAHIA (Environmental Hydrodynamics Base System), aiming the observation of the general aspects of the hydrodynamic circulation in different phases of tide (high tide, low tide, flood and ebb tide) in the Caeté estuary (PA) and like this validate, through the modeling, the facts (current, tides and amplitude of tide) collected in the estuary. The methodology was performed in two phases,( fieldwork and laboratory). The phase of fieldwork consisted of: (1) hoist bathymetric, linked to the Research’s Project of the SET PROGRAM/ CT-Hidro that utilized a cartographic base previously digitalized, having like base a satellite image LANDSAT-ETM+7, beyond a digital ecobatymetric and a DGPS (Differential Global Positioning System); (2) records of elevation of the sea level, through the fixation of two digital tide predictors Orphimedes OTT-Hydrometric, located in the Maguary city, where was observed daily values to each 20 minutes during 7 consecutive days with results varying of a minimum of 0,01 m to a maximum one of 5,08 m and of 0,42 to 5,18 in the point situated in the bridge about the hole of the Maguary and in the Bacuriteua city, respectively; and (3) measure the speed of the shackles utilizing a current predictor Falmouth 2D YMCA in a point inside the model, that stayed coupled to the boat during seven consecutive days and that presented values for the currents varying of a minimum of 2,95 cm/s to a maximum one of 154,59 cm/s. In the laboratory’s phase, was carried out the trial of calibration between the facts of the model with the measurements taken in the fieldwork. They were generated simulations of the hydrodynamics conditions during the flood, ebb tide, half tide flood, half tide ebb tide, and the high value of high tide and low tide, and in the neap and spring tides. Through those simulations were generated superficial maps of currents to see the different standards of circulation.