Análise da circulação do estuário do Rio Pirangi (CE) com o modelo Delft3D

Abstract

The estuary of the Pirangi River, located on the east coast of Ceará, is classified as a shallow estuary with a sandy bar, being under the influence of a semi-arid climate. During the dry period, the reduced flow transforms the Pirangi into a hypersaline estuary. The objective of this work is to analyze the circulation of the Pirangi River estuary using a hydrodynamic model. For this, a simulation was made using the Delft3D model of two scenarios of the circulation of the estuary and the adjacent coastal region for the year 2010 between the months of February-March and October-November, representing respectively the dry and wet periods in the region. As a forcing, local wind meteorological data were used uniformly across the domain area. In the open boundaries of the coastal region, the model was forced with the main tidal harmonic constituents of the region and in the upper extension of the estuary, a discharge with different flow and salinity values was added for each simulation. The estuary showed a flood-dominant tidal asymmetry. The maximum values of longitudinal velocity were 0.7 m/s for the flood and 0.6 m/s for the ebb. The residual velocity of the estuary didn't vary a lot in the dry period with values lower than 2 cm/s. In the wet season, the variation was approximately 11 cm/s at the surface and -1.5 cm/s at the bottom. The estuary showed a well-mixed profile vertically in both simulations, except for a small gradient along the coast during the wet season. There was a difference in the longitudinal salinity gradient between the simulations, the dry period values of salinity were higher in the estuary in relation to the ocean, and lower salinity values than the ocean in the wet season.