Modelling the Hydrodynamics of the Patos Lagoon, Brazil

Merged with duplicate record 10026.1/679 on 13.20.2017 by CS (TIS)The Patos Lagoon, the largest choked coastal lagoon in the world, is a typical centre of population, commerce, industry and recreation, and consequently it is also a site for disposal of industrial, agricultural and municipal wastes. Important questions concerning beneficial uses of and potential changes to the lagoon and its estuary are left unanswered without a good understanding of hydrodynamic processes. The current study involves the choice, calibration and application of a numerical model which can be used in future hydrodynamic. sediment transport and water quality studies in the area. The two- and three-dimensional modes of the TELEMAC System were chosen to study the hydrodynamics of the Patos Lagoon. In order to calibrate the TELEMAC-2D model for the lagoon, measurements of salinity, current speed and direction, water elevation and wind speed and direction were carried out simultaneously at three stations in the estuarine area during three days. The model validation was carried out against an independent data set from the 1998 El Nino event. Several two-dimensional simulations were carried out to investigate the main processes controlling the Patos Lagoon hydrodynamics. The model was forced with prescribed river inflow at the top of the lagoon, wind stress at the surface and water elevation at the ocean boundary. The barotropic pressure gradients established between the lagoon and the coastal area as a result of local and remote wind combined with the freshwater discharge, proved to be the main forces controlling the lagoon subtidal circulation, as well as the exchanges between the lagoon and the coast. The local wind dominates the lagoon circulation through the set-up/set-down mechanism of oscillation, whereas the non-local wind drives the circulation in the lower estuary. The entrance channel acts as a filter and strongly reduces tidal and subtidal oscillations generated offshore. Three-dimensional simulations proved to be essential. Studies of the processes involved in the estuarine transverse circulation showed that the wind drives the lateral flow in the shallow areas, whereas in the channel it depends on lateral pressure gradients and channel curvature and geometry. Insights on the estuarine baroclinic circulation indicate the barotropic forces as the main mechanism controlling salt water penetration and salinity structure in the estuary. This study produced valuable information into the forces controlling the circulation of the Patos Lagoon and its estuary. Important issues regarding the capabilities of the TELEMAC System two and three-dimensional modules were explored, producing a valuable tool for further hydrodynamic and sediment transport numerical modelling experiments

Hydraulic zonation of the lagoons of Marano and Grado, Italy. A modelling approach

The hydraulic regime-based zonation scheme of the Lagoons of Marano and Grado (Italy) has been derived by means of numerical models. A finite element modelling system has been used to describe the water circulation taking in account different forces such as tide, wind and rivers. The model has been validated by comparing the simulation results against measured water levels, salinity and water temperature data collected in several stations inside the lagoons. The analysis of water circulation, salinity and spatial distribution of passive tracers released at the inlets, led to a physically-based division of the lagoons system into six subbasins. The derived classification scheme is of crucial value for understanding the renewal capacity and pollutants distribution patterns in the lagoon

Downscaling With an Unstructured Coastal-Ocean Model to the Goro Lagoon and the Po River Delta Branches

The Goro Lagoon Finite Element Model (GOLFEM) presented in this paper concentrates on the high-resolution downscaled model of the Goro Lagoon, along with five Po river branches and the coastal area of the Po delta in the northern Adriatic Sea (Italy) where crucial socio-economic activities take place. GOLFEM was validated by means of validation scores (bias – BIAS, root mean square error – RMSE, and mean absolute error – MAE) for the water level, current velocity, salinity and temperature measured at several fixed stations in the lagoon. The range of scores at the stations are: for temperature between −0.8 to +1.2°C, for salinity from −0.2 to 5 PSU, for sea level 0.1 m. The lagoon is dominated by an estuarine vertical circulation due to a double opening at the lagoon mouth and sustained by multiple sources of freshwater inputs. The non-linear interactions among the tidal forcing, the wind and the freshwater inputs affect the lagoon circulation at both seasonal and daily time scales. The sensitivity of the circulation to the forcings was analyzed with several sensitivity experiments done with the exclusion of the tidal forcing and different configurations of the river connections. GOLFEM was designed to resolve the lagoon dynamics at high resolution in order to evaluate the potential effects on the clam farming of two proposed scenarios of human intervention on the morphology of the connection with the sea. We calculated the changes of the lagoon current speed and salinity, and using opportune fitness indexes related to the clams physiology, we quantified analytically the effects of the interventions in terms of extension and persistence of areas of the clams optimal growth. The results demonstrate that the correct management of this kind of fragile environment relies on both long-term (intervention scenarios) and short-term (coastal flooding forecasts and potential anoxic conditions) modeling, based on a flexible tool that is able to consider all the recorded human interventions on the river connections. This study also demonstrates the importance of designing a seamless chain of models that are capable of integrating local effects into the coarser operational oceanographic models

Development of an integrated system for coastal waters

This paper describes some of the needs and problems associated to assessment of coastal and estuarine problems (sediment transport and eutrophication). The development of an integrated system including EO data, local measurements with special emphasis on modeling tools, is presented as a solution for studying and helping decision making on the subject. Two pilot sites for the implementation and the present development status of the integrated system are depicted. This framework was already presented in a recent AO specific for Portugal, which is still under evaluation

Modeling circulation patterns induced by spatial cross-shore wind variability in a small-size coastal embayment

This contribution shows the importance of the cross-shore spatial wind variability in the water circulation in a small-sized micro-tidal bay. The hydrodynamic wind response at Alfacs Bay (Ebro River delta, NW Mediterranean Sea) is investigated with a numerical model (ROMS) supported by in situ observations. The wind variability observed in meteorological measurements is characterized with meteorological model (WRF) outputs. From the hydrodynamic simulations of the bay, the water circulation response is affected by the cross-shore wind variability, leading to water current structures not observed in the homogeneous-wind case. If the wind heterogeneity response is considered, the water exchange in the longitudinal direction increases significantly, reducing the water exchange time by around 20%. Wind resolutions half the size of the bay (in our case around 9 km) inhibit cross-shore wind variability, which significantly affects the resultant circulation pattern. The characteristic response is also investigated using idealized test cases. These results show how the wind curl contributes to the hydrodynamic response in shallow areas and promotes the exchange between the bay and the open sea. Negative wind curl is related to the formation of an anti-cyclonic gyre at the bay's mouth. Our results highlight the importance of considering appropriate wind resolution even in small-scale domains (such as bays or harbors) to characterize the hydrodynamics, with relevant implications in the water exchange time and the consequent water quality and ecological parameters.Peer ReviewedPostprint (author's final draft

Circulación baroclínica e inducida por viento en el puerto de Tarragona (España)

The sustainability of harbour management from an environmental standpoint is a current concern for port authorities. It includes dealing with problems that may affect the quality of in-harbour waters. In semi-enclosed basins, the characteristics of the circulation pattern are one of the main factors influencing the water quality, since they determine the residence time of pollutants inside the basin and govern the interaction between inside waters and the cleaner outside waters. Although harbour hydrodynamics are affected by the constant traffic of vessels and the physical constraints imposed by harbour structures, the water dynamics in ports are generally governed by three mechanisms: tidal forcing, wind surface stress, and baroclinic effects. This study presents the characterisation of winter circulation features in Tarragona harbour (northeast Spain), based on both field data and numerical simulations. Due to the microtidal nature of the Mediterranean Sea, three-dimensional water density distribution and local wind are expected to be the most relevant driving mechanisms. The results obtained suggest that, although wind effects may be important in determining the water flow in and out of the harbour for small time-scales, in the long term the most important water exchange mechanism is related to the waterbody’s baroclinic structure, with wind forcing playing only a second-order role. La gestión sostenible de los puertos desde un punto de vista ambiental es un tema de interés actual y un objetivo para las autoridades portuarias. Este tipo de administración incluye el tratamiento de problemas que pueden afectar a la calidad de las aguas interiores del puerto. En cuerpos de agua semicerrados, uno de los factores que más influye en la calidad del agua son las características del patrón de circulación, puesto que gobiernan la interacción entre aguas interiores y aguas exteriores más limpias, y determinan el tiempo de residencia de contaminantes dentro del recinto. Si bien las corrientes dentro de los puertos se ven afectadas continuamente por el tráfico de buques y por las restricciones físicas impuestas por las propias estructuras portuarias, la hidrodinámica general está dominada por tres mecanismos distintos: mareas, tensión de viento, y efectos baroclínicos. Este estudio presenta la caracterización de la circulación invernal en el Puerto de Tarragona (España), basada en datos de campo y en simulaciones numéricas. Debido al carácter micromareal del Mediterráneo, se espera que los forzamientos más relevantes sean el viento local y la distribución tridimensional de la densidad del agua. Los resultados obtenidos sugieren que, si bien los efectos del viento pueden ser importantes para determinar el flujo de agua hacia el interior del puerto para escalas de tiempo reducidas, a largo plazo el mecanismo más importante de intercambio de agua con el exterior está asociado a la estructura baroclínica del cuerpo de agua, siendo el forzamiento por viento un agente secundario

Wind and Tide-Induced Hydrodynamics and Sedimentation of Two Tidal Inlets in Western Greece

To quantify the detailed mechanisms that cause sedimentation at the tidal inlets in the Messolonghi-Aetoliko lagoonal system, the MIKE 21 FM (HD & ST) numerical simulation models were applied. The study focuses on the hydrodynamic circulation in the vicinity of the tidal inlets and the associated wind and tide-induced currents, as well as sediment transport, bed level evolution and total sediment load accumulation, with emphasis on the vicinity of two tidal inlets, where the problem is more acute. Based on the numerical predictions, which have been qualitatively corroborated via satellite images from Google Earth, it is shown that under the prevailing winds and tidal action, sandbars are formed in front or behind the tidal inlets depending on the wind direction, resulting in a gradual decrease of the mean water level at the mouths. Under the combined action of the tide and the wind the characteristic horizontal structure of the flow includes cyclonic and anti-cyclonic eddies that form at the near tip area of the jetties, which are associated with sediment transport mechanisms