Papers

This paper presents the technical decisions taken during the design and development of GESTBARRAGENS, which is an Information System that manages data concerning dam safety. We focus the discussion around its data analysis features, namely: (1) the generation of dynamic forms in ASP.NET; (2) the reporting mechanism implemented with MS Reporting Services; and (3) the spatial analysis based on a GIS infrastructure using the ESRI arcIMS tools.

Results of an experimental research into the physical, chemical, mechanical, and aesthetical changes suffered by pultruded glass-fiber-reinforced polyester profiles during their testing for accelerated aging under the action of moisture, temperature, and ultra violet (UV) radiation are presented. The profiles were submitted to the influence of four different exposure environments: (i) in an immersion chamber, (ii) in a condensation chamber, (iii) in a QUV accelerated weathering apparatus, and (iv) in a xenon-arc accelerated weathering apparatus. The results obtained were analyzed regarding the changes in their weight, sorption ability, tensile and flexural strength characteristics, color, and gloss; the chemical changes were investigated by means of Fourier-transform infrared spectroscopy. Considerable chromatic changes were observed, especially owing to the UV radiation. Although some reduction in the mechanical properties was observed, particularly in the immersion and condensation chambers, the durability tests proved a generally good behavior of this material under the aggressive conditions considered.

This paper investigates the effect of natural and artificial morphological changes in a tidal inlet on the tidal propagation and on the water exchanges with the sea, through data analysis and numerical modeling. Bathymetric and tidal data reveal a strong seasonal signal, as a result of the changes in the relative importance of tidal and wave action: during the maritime winter the M2 tidal amplitude decreases by 50% and flood dominance increases. This trend is reverted during maritime summer, and tidal amplitudes can be further enhanced by dredging of the inlet. Hydrodynamic and residence time (RT) simulations were set up for three different bathymetric configurations of the lower lagoon, representative of distinct situations. Hydrodynamic results confirmed that tidal propagation depends strongly on the bathymetric configuration. At the transitions between channels, tidal energy losses occur and flood dominance increases. Dredging the channels and repositioning the inlet throat improve tidal propagation and promote sediment flushing to the sea. The spatial variability of RTs was evaluated through the integration of individual particle results in morphologically relevant units, while time variability was examined within the tidal and neap/spring cycles. Residence times depend heavily on the morphological changes associated with both dredging operations and inlet migration, and on the particle release time, both within the tidal cycle and within neap/spring cycles. The relative importance of each of these factors depends on the particle location within the lagoon. The upstream regions of the lagoon have very large RTs (years), as a result of the small tidal amplitudes and velocities. In some of these regions, RTs vary by a factor of 4 depending on the bathymetry of the inlet. In the lower lagoon, tidal amplitude also has a significant effect on RTs. Dredging the channels and repositioning the inlet throat from the southern margin to a central position improves the flushing of both southern and northern channels.

O presente trabalho corresponde à primeira fase do projecto POCI/ECM/57909/2004 (2005-2008) - Avaliação de desempenho de Estações de Tratamento de Água e de Estações de Trata-mento de Águas Residuais, cujo objectivo é o estabelecimento de metodologias de avaliação de desempenho de sistemas de saneamento básico, nas suas vertentes de tratamento de água e de tratamento de águas residuais.Neste artigo apresenta-se a caracterização da situação na-cional em termos de estações de tratamento de água e de águas residuais relativamente a localização geográf ca, a ca-pacidade de tratamento, a tipos de tratamento mais comuns e a monitorização. Esta caracterização reveste-se de importância para o projecto atrás referido uma vez que irá permitir o estabelecimento dos cenários sobre os quais serão delineadas as metodologias de avaliação de desempenho.

A recarga é um processo importante a considerar na definição da sustentabilidade da exploração das águas subterrâneas. Contudo, a recarga não pode ser medida directamente, pelo que a sua quantificação constitui um processo estimativo que recorre a equações de balanço de massa. Estas equações traduzem o modelo conceptual de funcionamento hídrico de uma área de estudo, possibilitando a estimativa da recarga. O modelo conceptual depende da definição espaço-temporal das áreas de recarga, das áreas de descarga, das áreas onde pode ocorrer evapotranspiração a partir da zona saturada, dos limites do corpo hídrico subterrâneo, dos volumes de entrada de água no sistema em estudo, incluindo a precipitação, e das extracções e utilizações de água superficial e subterrânea e respectivas localizações. Nesta comunicação começa-se por se apresentar um modelo conceptual global e a respectiva equação de balanço hídrico, particularizando-se posteriormente para diversas situações que introduzem simplificações nas equações de balanço hídrico. Para os processos dessas equações que não são medidos directamente referem-se métodos de cálculo.

Hydrodynamics, salinity intrusion and stratification in the Guadiana estuary were characterized using two- and three-dimensional models for fresh water flows covering the range of monthly averaged river flows for dry to wet years. Two- and three-dimensional circulation model results were then used to investigate the flushing properties of the lower estuary for passive organisms and for organisms with vertical migration capabilities, respectively. Stratification can occur in the Guadiana estuary for river flows as small as 10 m3 s-1, depending on the tidal amplitude. For homogeneous or weakly stratified conditions, salinity can be found upstream of Alcoutim (km 40) during neap tides, and extends even further for spring tides. For a river flow of 10 m3 s-1, euhaline conditions reach 25 km upstream of the mouth during spring tides. For larger river flows, the region under stratified conditions is located in the downstream 10 km, and its extent depends mainly on the tidal phase. For river flows between 50 and 300 m3 s-1, salinity intrusion does not extend beyond km 20. As the river flow increases, the upper limits of the several haline regions approach one another, creating a lower estuary where salinity conditions have a wide range of horizontal variability. Residence times of passive organisms in the lower Guadiana estuary depend on the magnitude of the river flow, tides and other mechanisms, varying from a few hours to 60 days in the range of river flows considered. The variability of residence times with different environmental conditions is similar for all river flows, the upper limit of residence times being about one order of magnitude larger than the lower limit. For river flows above 200 m3 s1, both limits of residence times are small (from a few hours to a few days), showing the dominant role of river flow in these conditions. However, active organisms, with vertical migration capabilities, can remain inside the Guadiana estuary under strong river flows, by taking advantage of the phase lag along the vertical profiles of velocity under stratified conditions. Permanence conditions improve for organisms located in the main channel, due to the larger stratification in deeper areas. The tidal amplitude also plays an important role, spring tides being more favourable to permanence than neap tides.

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Internal solitary waves (ISWs), travelling towards the South South-West (SSW), are now well documented in the northern and central Bay of Biscay. These are formed from large-amplitude internal tides which result from the interaction of the barotropic tide with the steep shelf-break topography. In the present paper, we investigate available satellite imagery (Synthetic Aperture Radar (SAR) and ASAR data) to reveal that the southern Bay of Biscay is also a hotspot region which has a high level of ISW activity. Here, the ISWs travel towards the East North-East from the Cape Finisterre region off North-West Spain. In fact, we reveal the presence of two wave-trains travelling in slightly different directions (0551T and 0401T). By calculating the strength of the barotropic tidal forcing in the region, and identifying the likely propagation pathways (rays) of internal tidal (IT) energy, we identify the generation sites for these wave-trains as lying on either side of the Ortegal Promontory (OP). This is an undersea headland projecting towards the North-West from the north-western coast of Spain (near 441N, 8.51W), and over which the barotropic tides are forced to flow. For each generation site, IT rays emanating from critical topography (where the ray slope is equal to the topographic slope) in regions of strong barotropic forcing, rise to the surface (for one site after a reflection from the sea-floor) and pass through the thermocline close to the earliest occurrences of the ISWs in the respective wave trains. These rays would then produce, through nonlinear processes, the ISWs through the same local generation mechanism that has been used to explain the occurrence of the ISWs in the northern and central Bay. The local generation mechanism may therefore be more widely applicable than previously thought. In addition, the methods we have used to deduce the generation sites for these waves are expected to prove equally useful for studies in other areas of the world s oceans.

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