Caracterização e modelagem hidrodinâmica da circulação do sistema estuarino do rio Guaratuba (Bertioga - SP)
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Data
2019-03-12
Autores
Fey, Jésica Daniela
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Universidade Estadual Paulista (Unesp)
Resumo
Estuários são ambientes aquáticos de transição entre o continente e o oceano com características únicas, ecológica e economicamente importantes. São condicionados por diversas forçantes naturais e compartilham contribuições terrestres e marinhas. Os principais métodos para estudo hidrodinâmico desses ambientes baseiam-se na análise dos processos de advecção e de mistura das massas de água, gerados pela dinâmica das marés e das descargas dos rios. O presente estudo visa a caracterização hidrodinâmica do estuário do rio Guaratuba (Bertioga, SP) durante as marés de sizígia e de quadratura, a partir de levantamentos hidrográficos realizados com ADCP e CTD e o desenvolvimento de um modelo hidrodinâmico computacional capaz de explicar e simular os processos oceanográficos deste estuário. Os resultados apontaram que, tanto a maré quanto a descarga fluvial têm a capacidade de alterar as vazões e os padrões de salinidade e temperatura no estuário. Em condições de precipitação médias ou na ausência de precipitações, a maré é a forçante dominante do sistema. Durante os períodos de sizígia ocorrem o aumento da turbulência e da mistura vertical. Nas quadraturas, quando as velocidades de corrente são menores, a estratificação vertical é mais estável, e a água salina incursiona até pontos mais internos do estuário. Precipitações na sub-bacia tem relação direta e imediata com o aumento da vazão, afetando a dinâmica e intensificando a estratificação vertical do estuário. O estuário do rio Guaratuba pode ser enquadrado como do tipo A, B ou D, dependendo das condições de maré e vazão. Os modelos gerados contribuíram para o melhor entendimento dos fenômenos atuantes e da dinâmica do sistema estuarino. Os resultados do presente trabalho trazem informações inéditas sobre o comportamento hidrodinâmico do estuário do Rio Guaratuba durante marés de quadratura e podem ser utilizados pelos gestores e tomadores de decisão para orientar o uso sustentável desse ambiente, no que tange ao gerenciamento costeiro e de recursos hídricos.
Estuaries are transitional aquatic environments, with unique characteristics, ecologically and economically important. They are conditioned by several natural forcings and share land and marine contributions. The main methods to study these environments are based on the analysis of the water masses advection and mixing processes, that are generated by tides and river discharges. The purposes of this study are the hydrodynamic characterization of the Guaratuba’s estuary (Bertioga, SP) during spring and neap tides, based on ADCP and CTD hydrographic surveys, and the development of a computational hydrodynamic model using Delft-3D software, that helps to explain and simulate the main estuarine oceanographic processes. We observed that both, tide and river discharges, have the capacity to alter water flow, as well as salinity and temperature patterns in the estuary. Under mean precipitation conditions or in its absence, tide forces dominate the system. During the spring tide floods, turbulence and vertical mixing increase. During the neap tide floods, when current speed decreases, vertical stratification remains more stable, and saline water penetrates more along the upper estuary. Precipitation episodes in the sub-basin are direct and immediate related to water flow increase, and affect currents dynamics intensifying vertical stratification in the estuary. The Guaratuba estuary is classified as type A, B or D; depending on tidal and river flow conditions. The models we generated contributed to understanding active phenomena and the dynamics of the estuarine system. The results of the present study provide valuable new information on the estuarine hydrodynamic behavior during neap tides, and might be used by managers and decision makers to guide the sustainable use of this environment, regarding coastal and water resources management.
Estuaries are transitional aquatic environments, with unique characteristics, ecologically and economically important. They are conditioned by several natural forcings and share land and marine contributions. The main methods to study these environments are based on the analysis of the water masses advection and mixing processes, that are generated by tides and river discharges. The purposes of this study are the hydrodynamic characterization of the Guaratuba’s estuary (Bertioga, SP) during spring and neap tides, based on ADCP and CTD hydrographic surveys, and the development of a computational hydrodynamic model using Delft-3D software, that helps to explain and simulate the main estuarine oceanographic processes. We observed that both, tide and river discharges, have the capacity to alter water flow, as well as salinity and temperature patterns in the estuary. Under mean precipitation conditions or in its absence, tide forces dominate the system. During the spring tide floods, turbulence and vertical mixing increase. During the neap tide floods, when current speed decreases, vertical stratification remains more stable, and saline water penetrates more along the upper estuary. Precipitation episodes in the sub-basin are direct and immediate related to water flow increase, and affect currents dynamics intensifying vertical stratification in the estuary. The Guaratuba estuary is classified as type A, B or D; depending on tidal and river flow conditions. The models we generated contributed to understanding active phenomena and the dynamics of the estuarine system. The results of the present study provide valuable new information on the estuarine hydrodynamic behavior during neap tides, and might be used by managers and decision makers to guide the sustainable use of this environment, regarding coastal and water resources management.
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Palavras-chave
pluviosidade, vazão, estratificação da salinidade, dinâmica estuarina, Delft-3D, Parque Estadual Restinga de Bertioga, precipitation, water flow, salinity stratification, estuarine dynamics, Delft-3D, Restinga de Bertioga State Park