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- EU water framework directive: will the nitrate load reduction from diffuse sources produce the same results in all estuaries?Publication . Martins, Flávio Augusto Bastos da CruzThe impact of urban waste-water and non-point nitrate discharges in estuarine and near-shore coastal waters are analyzed. The study is focused on the effects of applying the European directives 91/271/EEC and 91/676/EEC to these systems. 4 Portuguese estuaries and two coastal lagoons with different characteristics are studied. A modelling system is applied and calibrated in each system. Three nitrate load scenarios are examined. It is shown that the morphologic and hydrodynamic characteristics of the domain largely control the ecological processes in these systems. The primary production limitation factors are split into “biologic” and “hydrodynamic” components. The physical limitation due to hydrodynamic and residence time is the most important factor. The combined limitation of “biologic” factors (temperature, light and nutrients availability) control productivity only in the systems where physical limitation is not important.
- Hydrodynamic model intercomparison for the patos lagoon (Brazil)Publication . Martins, Flávio Augusto Bastos da Cruz; Fernandes, Elisa H. L.An intercomparison study is carried out between two models with different formulations and spatial discretizations in order to overcome the limitations posed by the standard calibration and validation procedures and improve confidence in the hydrodynamic results for the Patos Lagoon. Numerical simulations were carried out applying the TELEMAC and MOHID models, based on the same boundary conditions and identical calibration coefficients so differences in calculated flow conditions result from the formulations and parameterizations of each model. Results from both models are compared with measurements from three stations inside the lagoon. Preliminary results indicate that both models compare well with the measurements and with each other. These results increase the confidence on hydrodynamic results for the Patos Lagoon and provide the first step towards water quality studies for the area.
- Metodologia de gestão dinâmica do estuário do SadoPublication . Caeiro, S.; Martins, Flávio Augusto Bastos da Cruz; Costa, Maria H.; Painho, M.; Neves, R.O estuário do Sado é um sistema litoral onde existem conflitos de gestão ambiental, uma vez que por um lado, localiza-se junto da zona industrial da Península de Setúbal e por outro lado, uma grande parte da sua área está classificada como Reserva Natural. Sendo uma área de especial sensibilidade, torna-se necessário implementar modelos de gestão, que passam pela elaboração de metodologias que avaliem o estado de qualidade da zona costeira. O objectivo deste trabalho é apresentar uma metodologia conceptual de gestão do estuário do Sado, ligado a um modelo dinâmico e ecológico suportado por uma infraestrutura de informação do tipo DPSIR e com base num sistema SIG (Sistema de Informação Geográfica). Desta forma pretende-se integrar a avaliação da qualidade do ecossistema, com base em indicadores da qualidade ambiental previamente seleccionados, com informação socio-económica. Nesta metodologia as propostas de intervenção e a avaliação do seu impacte no estuário são baseadas nos dados ambientais recolhidos e nas previsões dos efeitos dessas acções. Pretende-se que a modelação dinâmica e ecológica do sistema desempenhe um papel fundamental tanto na caracterização do estuário como nas propostas de intervenção. A simulação permite a caracterização do sistema, a comparação de cenários alternativos e a quantificação do impacte de acções de intervenção. Os dados de campo e os resultados da modelação são integrados numa plataforma comum que facilite o relacionamento e o cruzamento de toda a informação. Esta metodologia permitirá assim a elaboração de uma interface de suporte à gestão/decisão do Estuário do Sado para entidades com poder de decisão sobre este ecossistema.
- Influence of the Barrie de la Maza dock on the circulation pattern of the Ría of a Coruña (NW-Spain)Publication . Gómez-Gesteira, Moncho; Decastro, Maite; Prego, Ricardo; Martins, Flávio Augusto Bastos da CruzA 3D hydrodynamical model is applied to the ria of A Coruña to analyze the evolution of the circulation pattern in the ria after the building of a breakwater (Barrie de la Maza dock) in the sixties. This circulation pattern has changed greatly. On the one hand, the circulation, which was almost parallel to the shore line under the original conditions, now shows a gyre near the end of the dock. On the other hand, a considerable increase (about 30%) in the velocities near the end of the breakwater and in the main channel of the estuary has been observed after the building of the dock. A stronger bottom shear stress has been generated in the estuary areas where the velocity increased. The bottom shear stress increase was particularly great (over 100%) near the end of the dock. This increase in the shear stress produced bottom erosion and matter resuspension, and consequently major changes in the bathymetry. In addition, in situ sedimentary measurements carried out by Lopez-Jamar (1996) corroborate the bottom erosion in the main chanel of the estuary and at the end of the dock produced by the velocity increase generated by the building of the breakwater.
- Modelação ecológica no estuário do SadoPublication . Martins, Flávio Augusto Bastos da CruzOs modelos matemáticos são ferramentas poderosas para avaliar o impacto humano em sistemas costeiros e estuarinos de estrutura complexa. Neste artigo utiliza-se um sistema de modelos matemáticos para simular o comportamento hidrodinâmico e biológico do estuário do Sado. Estudos experimentais de análise da evolução da biomassa de fitoplâncton durante os últimos 10 anos indicam que o ecossistema se encontra numa situação relarivamente estável, exibindo pouca tendência para a eutrofização (Cabeçadas, 1993). Neste Artigo procura-se caracterizar o estado trófico do sistema, confirmar as conclusões obtidas experimentalmente e interpretar os processos que ocorrem na região do estuário.
- Combining sampling, profiling, remote sensing and modelling to efficiently monitoring estuarine and coastal water qualityPublication . Martins, Flávio Augusto Bastos da CruzMonitoring of coastal and estuarine water quality has been traditionally performed by sampling with subsequent laboratory analysis. This has the disadvantages of low spatial and temporal resolution and high cost. In the last decades two alternative techniques have emerged to overcome this drawback: profiling and remote sensing. Profiling using multi-parameter sensors is now in a commercial stage. It can be used, tied to a boat, to obtain a quick “picture” of the system. The spatial resolution thus increases from single points to a line coincident with the boat track. The temporal resolution however remains unchanged since campaigns and resources involved are basically the same. The need for laboratory analysis was reduced but not eliminated because parameters like nutrients, microbiology or metals are still difficult to obtain with sensors and validation measurements are still needed. In the last years the improvement in satellite resolution has enabled its use for coastal and estuarine water monitoring. Although spatial coverage and resolution of satellite images in the present is already suitable to coastal and estuarine monitoring, temporal resolution is naturally limited to satellite passages and cloud cover. With this panorama the best approach to water monitoring is to integrate and combine data from all these sources. The natural tools to perform this integration are numerical models. Models benefit from the different sources of data to obtain a better calibration. After calibration they can be used to extend spatially and temporally the methods resolution. In Algarve (South of Portugal) a monitoring effort using this approach is being undertaken. The monitoring effort comprises five different locations including coastal waters, estuaries and coastal lagoons. The objective is to establish the base line situation to evaluate the impact of Waste Water Treatment Plants design and retrofitting. The field campaigns include monthly synoptic profiling, using an YSI 6600 multi-parameter system, laboratory analysis and fixed stations. The remote sensing uses ENVISAT\MERIS Level 2 Full Resolution data. This data is combined and used with the MOHID modelling system to obtain an integrate description of the systems. The results show the limitations of each method and the ability of the modelling system to integrate the results and to produce a comprehensive picture of the system.
- Hydroinformatics based decision.making integrating modelling, sampling and profiling: the Ria Formosa casePublication . Venâncio, A.; Martins, Flávio Augusto Bastos da Cruz; Neves, R.A Waste Water monitoring program aiming to help decision making is presented. The program includes traditional and inboard sensor sampling, hydrodynamic and water quality modeling and a GIS based database to help the decision making of manager authorities. The focus is in the quality of waters receiving discharges from Waste Water Treatment Plants. Data was used to feed model simulations and produce hydrodynamic, effluent dispersion and ecological results. The system was then used to run different scenarios of discharge flow, concentration and location. The results enable to access the current water quality state of the lagoon and are being used as a decision making tool by the waste water managers in the evaluation phase of the treatment plant project to decide the location and the level of treatment of the discharge.
- A methodology to estimate the residence time of estuariesPublication . Braunschweig, Frank; Chambel, Paulo; Martins, Flávio Augusto Bastos da Cruz; Neves, R.The residence time has long been used as a classification parameter for estuaries and other semi- enclosed water bodies. It aims to quantify the time water remains inside the estuary, being used as an indicator both for pollution assessment and for ecological processes. Estuaries with a short residence time will export nutrients from upstream sources more rapidly then estuaries with longer residence time. On the other hand the residence time determines if micro-algae can stay long enough to generate a bloom. As a consequence, estuaries with very short residence time are expected to have much lower algae blooms, then estuaries with longer residence time. In addition, estuaries with residence times shorter than the doubling time of algae cells will inhibit formation of algae blooms (EPA, 2001). The residence time is also an important issue for processes taking place in the sediment. The fluxes of particulate matter and associated adsorbed species from the water column to the sediment depends of the particle’s vertical velocity, water depth and residence time. This is particularly important for the fine fractions with lower sinking velocities. The question is how to compute the residence time and how does it depend on the computation method adopted.
- Coupling anchovy eggs and hydrodynamic model as an assessement tool for estuarine ecohydrological managementPublication . Morais, P.; Chicharo, Maria Alexandra; Martins, Flávio Augusto Bastos da Cruz; Chícharo, Luís; Lopes, J.Nitrate and urban waste water directives have raised the need for a better understanding of coastal systems in European Union. The incorrect application of these directives can lead to important ecological or social penalties. In the paper this problem is addressed to Ria Formosa Coastal Lagoon. Ria Formosa hosts a Natural Park, important ports of the southern Portuguese coast and significant bivalve aquaculture activity. Four major urban waste water treatment plants discharging in the lagoon are considered in this study. Its treatment level must be selected, based on detailed information from a monitoring program and on a good knowledge of the processes determining the fate of the material discharged in the lagoon. In this paper the results of a monitoring program and simulations using a coupled hydrodynamic and water quality / ecological model, MOHID, are used to characterise the system and to understand the processes in Ria Formosa. It is shown that the water residence time in most of the lagoon is quite low, of the order of days, but it can be larger in the upper parts of the channels where land generated water is discharged. The main supply of nutrients to the lagoon comes from the open sea rather than from the urban discharges. For this reason the characteristics and behaviour of the general lagoon contrasts with the behaviour of the upper reaches of the channels where the influence of the waste water treatment plants are high. In this system the bottom mineralization was found to be an important mechanism, and the inclusion of that process in the model was essential to obtain good results.
- Influence of the Barrie de la Maza dock on the circulation pattern of the Ria of A Coruna (NW-Spain)Publication . Gomez-Gesteira, M; Decastro, M; Prego, R; Martins, FlávioA 3D hydrodynamical model is applied to the ria of A Coruna to analyze the evolution of the circulation pattern in the ria after the building of a breakwater (Barrie de la Maza dock) in the sixties. This circulation pattern has changed greatly. On the one hand, the circulation, which was almost parallel to the shore line under the original conditions, now shows a gyre near the end of the dock. On the other hand, a considerable increase (about 30%) in the velocities near the end of the breakwater and in the main channel of the estuary has been observed after the building of the dock. A stronger bottom shear stress has been generated in the estuary areas where the velocity increased. The bottom shear stress increase was particularly great (over 100%) near the end of the dock. This increase in the shear stress produced bottom erosion and matter resuspension, and consequently major changes in the bathymetry. In addition, in situ sedimentary measurements carried out by Lopez-Jamar (1996) corroborate the bottom erosion in the main chanel of the estuary and at the end of the dock produced by the velocity increase generated by the building of the breakwater.
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