Oscilação do nível de água e a co-oscilação da maré astronômica no baixo estuário do rio Paraíba do Sul, RJ

Abstract

ABSTRACT. The water level in the lower Paraíba do Sul river estuary was assessed in order to evaluate the effects of the astronomical tide co-oscillation, river discharge and meteorological events. Water level data was recorded hourly from October 2000 until February 2003 at a gauge station nearby the estuarine inlet. The water level is controlled mainly by the astronomical tide co-oscillation during periods of low river discharge, and eventually by meteorological tides. Even during periods of higher river discharge the water level is controlled by astronomical co-oscillation, although during low tide phase the river discharge effects are observable. During periods of extreme high discharge the low frequency water level is mainly driven by the river inflow. The tidal wave was mostly symmetrical during the low river discharge periods, and asymmetries were observed during meteorological events, with shorter flood and longer ebbs. Although, such effects were not corroborated by astronomical tidal constituents M 2 and M 4 relationship, which suggests ebb dominance. Stronger distortions were observed during high discharge periods, with tide attenuation either at neap as in spring tide periods. During these periods the asymmetries were corroborated by M 2 and M 4 relationship.Keywords: tidal asymmetry, meteorological tides, river discharge. RESUMO.A variabilidade do nível daágua no baixo estuário do rio Paraíba do Sul foi estudada para avaliar os efeitos da co-oscilação da maré astronômica, descarga fluvial e de eventos meteorológicos. Dados de nível daágua foram registrados em intervalos horários para o período entre outubro de 2000 até fevereiro de 2003 em uma estação localizada próximoà desembocadura do estuário. Foi observado que durante os eventos de descarga fluvial baixa os níveis deágua do estuário oscilam principalmente em função da co-oscilação da maré astronômica e eventualmente por marés meteorológicas. Durante períodos de descarga fluvial alta o nível daágua de preamar no baixo estuárioé dominado pela co-oscilação, enquanto que nas baixa-maresé influenciado pela descarga fluvial. Em períodos de descarga fluvial muito alta o estuário passa a receber a influência tanto da descarga fluvial quanto da maré astronômica nas oscilações do nível. Em períodos de baixa descarga quase não houve modificação na onda de maré, sendo observada pequena assimetria no sentido de vazante. Ainda em baixa descarga, eventos de maré meteorológica produzem distorções e assimetrias, com o tempo de subida menor que o de descida, gerando correntes mais fortes no sentido de enchente. Contudo, isto não pôde ser confirmado com a relação de fase entre M 2 e M 4 , que sugeriu domínio de vazante. A descarga fluvial alta causou fortes distorções na onda de maré em períodos de quadratura e uma atenuação considerável nas amplitudes tanto de sizígia como de quadratura, com assimetrias no sentido de vazante corroboradas pela relação de fase entre M 2 e M 4 .Palavras-chave: assimetria de maré, marés meteorológicas, descarga fluvial.

Indicadores Biológicos De Ecossistemas Aquáticos

“…However, it should be noted that even at low tide there are still differences between the waters of points 1 and 2 in relation to the waters of further upstream points, which emphasizes that the sea has significant influence in this estuary during the low flow condition of the river. These results highlight the influence of the tidal semidurnal cycle on the limnological characteristics in a low fluvial flow condition, as already pointed out in other studies (Gonçalves, 2003;Sterza & Fernandes, 2006;Nicolite, et al, 2009) and they warn us that if these low flow conditions are maintained, the river could no longer have a water exchange regime in its estuary per flow pulse and could be having a water exchange regime per tidal cycle. Figure 4 synthesizes the horizontal gradient formation dynamic between the river and the sea water in this estuary.…”

“…As already known in the literature on the subject (Nicolite, et al, 2009), the estuary of the PSR presents the highest tide levels in the period between 1 day before and 2 days after the night of full moon and the night of new moon. Thus, the measurements of this work were always made in this time interval at the time of the high tide and the low tide.…”

“…The estuary of Paraíba do Sul river (PSR) is strongly governed by flow pulses (Nicolite et al, 2009;Cotovicz Jr. et al, 2013 and it can be classified as coastal wetland separated from the sea with fluctuating water level (Junk et al, 2014). This river is 1,155 km long and drains an area of 55400 km² (Coelho, 2012), and its estuary has a surface area of 21.5 km², an average depth of 2 m, a 43.1 × 106 m³ volume and a hydraulic residence time of 0.75 days (Sterza, Fernandes, 2006;Cotovicz Jr., et al, 2013).…”

“…This river is 1,155 km long and drains an area of 55400 km² (Coelho, 2012), and its estuary has a surface area of 21.5 km², an average depth of 2 m, a 43.1 × 106 m³ volume and a hydraulic residence time of 0.75 days (Sterza, Fernandes, 2006;Cotovicz Jr., et al, 2013). The morphosedimentary design of the RSP estuary is dominated by waves (Oliveira, 2015), and this estuary is located in a humid tropical climate and subject to a semidiurnal micro-tidal regime (Nicolite, 2009;Bernardes et al, 2012, Alvares, et al, 2013. According to Cotovicz Jr. et al (2013), approximately 46.1% of the RSP estuary area is composed of fresh water, 33.2% of brackish water and 20.7% of saline water, but these values can be changed between dry and rainy season.…”

Comparative analysis of rating curve and ADP estimates of instantaneous water discharge through estuaries in two contrasting Brazilian rivers

“…Besides the dominant seasonal variations the outflows may present variability of the order of days, in response to abnormal rainfalls in the drainage basin. Classic examples of the use of outflow estimates (obtained through the stage–discharge curve) for the calculation of fluxes of suspended sediments and various materials that are transported through the drainage basin to the nearby coastal area may be observed in (Nicolitte et al , 2009; Medeiros and Kjerfve, 1993; Molisani et al , 2007; Petersen‐Overleir, 2005; Santos et al , 2009). The authors use the outflow estimates that were obtained, on average, up to 30 km from the estuaries' mouth to calculate the import and/or export of materials to the adjacent coastal zone, neglecting important factors for the estuarine dynamics, such as lateral and bottom friction, wind stress, barotropic and baroclinic components of the gradient pressure force (per unit mass) and tide co‐oscillation, which can generate large uncertainties in these estimates, underestimating and/or overestimating the transport of materials from the drainage basin to the adjacent ocean.…”