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The consumption of nutrients by mussel beds can be monitored by measuring the net nutrient flux across a circumscribing vertical surface. Measuring this nutrient flux not only requires resolving the spatial (and temporal) distribu...
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The consumption of nutrients by mussel beds can be monitored by measuring the net nutrient flux across a circumscribing vertical surface. Measuring this nutrient flux not only requires resolving the spatial (and temporal) distribution of nutrients at the bounding contour, but also an ability to unambiguously measure net water motion across it. As a prerequisite for future application to nutrient flux determination, we here describe results of a field campaign in the inland Wadden Sea in which we aim to measure just the latter water balance. This is done by comparing the water transport across a vertical surface, spanned by the closed contour and the bottom, to the net tidal displacement of the free surface enclosed by this contour. The former is obtained by measuring currents while traversing the contour repeatedly within one tidal cycle. The latter is estimated using sea-level observations at nearby tidal stations as well as by means of direct sea-level observations at the location of measurements. The current measurements are used to reveal the spatial structure of the tidal and tidally rectified fields, which are divided into cross and along contour currents. These measurements show how the presence of a steep slope in the bathymetry has an impact on the presence of circulation cells that are relevant for the mixing and flushing of water. A neat closure of the water budget is obstructed since it is dominated by the difference between a strong inflow and a concurrent, nearly equally strong outflow. For future application we recommend using observed tidal elevations within the closed contour as a constraint in determining the best estimates for cross-contour water fluxes, thus opening the route to genuine nutrient flux measurements by 'contour integration'.
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Le sonar à effet Doppler « Argonaut shallow water » est conçu spécialement pour une installation à poste fixe en fond de rivière, de canal ou de port. Il permet des mesures en continu (ou tout au moins à pas de temps fins)...
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Le sonar à effet Doppler « Argonaut shallow water » est conçu spécialement pour une installation à poste fixe en fond de rivière, de canal ou de port. Il permet des mesures en continu (ou tout au moins à pas de temps fins) de la vitesse de l'eau en 2D (longitudinale et verticale). La vitesse de l'eau est mesurée par deux faisceaux, amont & aval, et une cellule verticale permet de mesurer la hauteur d'eau. La mesure de vitesse est intégrée sur la hauteur d'eau au droit du capteur. Le débit est calculé à partir de cette vitesse moyenne, combinée avec l'aire de la section mouillée, calculée à partir de la mesure du niveau et de l'information sur la géométrie de la section. Selon le constructeur, cet appareil n'exige aucun étalonnage(en vitesse) et les développements biologiques qui peuvent avoir lieu en surface n'affectent pas la précision de l'appareil. L'étude présentée ici, vise donc à évaluer la fiabilité de ce type d'appareil dans une section où l'écoulement est contrasté et où les effets du transport sont importants. On s'attarde plus spécifiquement à comparer les résultats obtenus, avec ceux issus d'une courbe de tarage existante. La section de mesure est équipée d'un double déversoir ce qui permet d'avoir une sensibilité différente pour les hautes et basses eaux. Si les tests montrent que l'équipement est fiable et peut apporter des informations supplémentaires, il en ressort aussi que l'efficacité et la qualité de la mesure en basse et très basse eaux sont défaillantes. Et qu'il est toujours aussi difficile de mesurer les bas débits...
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The dynamics of Bonifacio strait (south of Corsica) are investigated in a comprehensive study at long term from two set of data. First, by moored ADCP put in middle of the strait during six weeks (4 November 2004 to 7 January 2005...
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The dynamics of Bonifacio strait (south of Corsica) are investigated in a comprehensive study at long term from two set of data. First, by moored ADCP put in middle of the strait during six weeks (4 November 2004 to 7 January 2005), at a depth of 40 m and at few Kilometers from coast. Second, by velocity profiles obtained with a 314.4. kHz Acoustic Doppler Current Profiler (ADCP) during seven cruises (Cyrce) covering entirety strait. From moored ADCP data, a study is made on time correlation between wind stress and current. Shipboard ADCP data permits to obtain a general view in totality of strait and mostly to observe spatial variability. This study shows that the circulation is governed both by wind stress and by general circulation of Mediterranean Sea.
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A one-dimensional, steady state numerical model is developed for estimatingcross-shore surface transport in shallow waters, where the water depth is comparable toboundary layer thickness. The model is used to solve a momentum equa...
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A one-dimensional, steady state numerical model is developed for estimatingcross-shore surface transport in shallow waters, where the water depth is comparable toboundary layer thickness. The model is used to solve a momentum equation whichdescribes the cross-shore balance. To validate the model, acoustic Doppler current profiler(ADCP) current data collected during an experiment off the New Jersey shelf in thesummer of 1996 are used to estimate the cross-shore surface transport during that periodand then compared with model predictions based on the local wind. The success of themodel in estimating the cross-shore surface transport leads to an improved version of theconventional upwelling index (i.e., the Bakun Index), particularly for coastal areaswith wide and shallow shelves, such as the east coast of the United States. Finally, themodel, because of its simplicity, is well suited for operational applications wherecomputational resources may be limited.
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Using the ADCP (acoustic Doppler current profiler) and CTD (conductivity-temperature-depth probe) data obtained in the first CREAMS (Circulation Research of the East Asian Marginal Seas) cruise, we have investigated the cyclonic c...
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Using the ADCP (acoustic Doppler current profiler) and CTD (conductivity-temperature-depth probe) data obtained in the first CREAMS (Circulation Research of the East Asian Marginal Seas) cruise, we have investigated the cyclonic circulation in the Japan Basin (northern part of the Japan Sea), its volume transport and the spatial distribution of the currents. The current pattern and the distribution of the water mass with low salinity and low potential vorticity reveal the existence of a basin-wide cyclonic circulation in the Japan Basin. Its westward volume transport along the Russian coast from the surface to 300 m depth is estimated to be 1.0-1.5 Sv (1 Sv = 10~6 m~3/sec), increasing as it flows westward. ADCP results show that the cyclonic circulation is found even below the main pycnocline, and its vertical velocity is small there. The water mass with low salinity and low potential vorticity moves along this cyclonic circulation in the intermediate layer. This water mass flows eastward along the isobath of the northern edge of the Yamato Rise. This suggests that the cyclonic circulation is affected by the bottom topography since it reaches the deep layer. Some parts of this water mass move southward above the Yamato Rise.
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High-flow data are among the most important types of information for river flood control and water management. An acoustic Doppler current profiler (ADCP), tethered boat, and remotely operated drive are designed as an alternate fl...
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High-flow data are among the most important types of information for river flood control and water management. An acoustic Doppler current profiler (ADCP), tethered boat, and remotely operated drive are designed as an alternate flow measurement system. Regular- and high-flow measurements were conducted with traditional Price current meter and ADCP to evaluate the accuracy of measurement. The results indicate that the ADCP data are consistent with the current-meter data. Moreover, the ADCP measurements successfully represented the rising and falling stages of the typhoon flood. These results demonstrate that the developed measurement system is practical for river flow measurement.
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During August, NIWA hosted over thirty people at a two-day workshop on RDI ADCPs in Christchurch. Hening Huang was in attendance from RDI, leading most of the workshop, with Andrew Willsman from NIWA also proving some useful New Z...
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During August, NIWA hosted over thirty people at a two-day workshop on RDI ADCPs in Christchurch. Hening Huang was in attendance from RDI, leading most of the workshop, with Andrew Willsman from NIWA also proving some useful New Zealand experience of ADCPs.
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Abstract The moving‐boat Acoustic Doppler Current Profiler (ADCP) gauging method is extensively used to measure the discharge of rivers and canals. Informed decisions related to water management require reliable estimates of the ...
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Abstract The moving‐boat Acoustic Doppler Current Profiler (ADCP) gauging method is extensively used to measure the discharge of rivers and canals. Informed decisions related to water management require reliable estimates of the uncertainty of such measurements. The evaluation of the uncertainty is however a difficult task because of the complexity of the ADCP data workflow and the lack of reference discharges in rivers and canals. This study presents an evolution of the OURSIN method, which follows the framework of the Guide to the expression of Uncertainty in Measurement. The method has been implemented in the QRevInt software which provides an ADCP data quality review prior to the uncertainty analysis. As a computationally efficient alternative to the Monte Carlo approach, the uncertainty propagation combines elemental measurement uncertainty sources, transect‐to‐transect discharge variability, and estimation of the uncertainty of discharges in unmeasured areas by sensitivity analysis. The OURSIN uncertainty results are validated using empirical uncertainty estimates from two large‐scale repeated measures experiments with variable site and flow conditions. The mean and the 95% quantiles of the uncertainty differences are −0.4% [−4.4%; +2.5%]. The OURSIN method provides a comprehensive uncertainty budget that is helpful for understanding the relative impacts of error sources and defining strategies to minimize them. The method should be further evaluated with experiments in different conditions, and additional uncertainty components and options such as GPS reference for boat velocity could be implemented.
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Repeated measures experiments can be conducted to empirically estimate the uncertainty of a stream gauging method, such as the widespread moving-boat acoustic Doppler current profilers (ADCPs) approach. Previous ADCP repeated meas...
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Repeated measures experiments can be conducted to empirically estimate the uncertainty of a stream gauging method, such as the widespread moving-boat acoustic Doppler current profilers (ADCPs) approach. Previous ADCP repeated measures experiments, also known as interlaboratory comparisons, provided a credible range of uncertainty estimates reflecting the quality of the site conditions. However, the method, which is a one-way analysis of variance, only addresses the uncertainty of one lumped factor that combines several distinct factors: instrument, operator, procedure, and cross-section effects. To decompose the uncertainty of ADCP streamflow measurements due to cross-section selection and team effects, a large repeated measures experiment has been conducted in the Taurion River (France). The experiment design was crossed and balanced, with two sets of 24 teams circulated over two sets of 12 cross sections. A constant flow rate was released from a dam, located immediately upstream of the experimental site. Prior to the statistical analysis, a data quality review was performed using the U.S. Geological Survey QRev software to clean the data set from avoidable errors and to homogenize the discharge computations. A two-way analysis of variance was applied to quantify the cross-section effect, the team effect, and their interaction, which was found to dominate the pure cross-section effect. It was then possible to predict the average uncertainty of multiple-transect ADCP discharge measurements, depending on the number of teams, cross sections, and repeated transects included in the discharge average. The method opens interesting avenues for documenting difficult-to-estimate uncertainty sources of stream gauging techniques in other measuring conditions, especially the most adverse ones.
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