Avaliação da hidrodinâmica do estuário do Rio Itanhém (BA) sob diferentes condições de marés e de morfologia da desembocadura

Abstract

The objective of this study is to characterize the hydrodynamics of the Itanhém Estuary (BA), under different morphology conditions. Data from four campaigns were analyzed. The campaigns lasted one tidal cycle and they were carried out comprising spring and nead tidal conditions, in August 2007 and January 2008. Information of water level, current speed and direction, salinity, temperature and turbidity were recorded in a fixed station. Longitudinal survey data were also analyzed: salinity, temperature and turbidity were registered every kilometer. In 2007, there was a sandy spit at the estuary mouth, which displaced the mouth of the estuarine channel. In January 2008, the spit was broken, approaching the mouth of the fixed station. Tidal asymmetry was identified in the estuary, which is more pronounced under spring tidal conditions. The estuary was flood-dominated in 2007, and ebb-dominated in 2008. A possible cause of this reversal is the change in the morphology, which may have affected the storage capacity of intertidal estuary. The average vertical profiles of salinity also showed inversion between 2007 (positive average velocity) and 2008 (negative average velocity), results consistent with the reversal of asymmetry. The stability of the water column changed between 2007 and 2008, with a predominance of stability in 2007 and instability in 2008. Saltwater intrusion has advanced about 6 km in spring tide conditions. The maximum turbidity zone also advanced. In 2008, the longitudinal surveys were performed at high tide, and the extent of seawater was higher than in 2007, the year in which the profiles occurred at low tide. The variation in the morphology of the river mouth was the possible cause of changes in hydrodynamic characteristics evaluated in this estuary.