Yves Secretan | Institut national de la recherche scientifique (original) (raw)
Papers by Yves Secretan
Canadian Water Resources Journal, 2003
The St. Lawrence River is one of the most important large rivers in North America. This 600-km lo... more The St. Lawrence River is one of the most important large rivers in North America. This 600-km long watercourse is characterized by a high degree of physical heterogeneity, including fast moving narrow reaches separated by fluvial lakes reaching 10 km in width. The mean annual discharge from the outflow of Lake Ontario is 7500 m 3 /s and has been managed for hydropower and transportation since the 1960s. With the management plan currently under review an effort is being made to include criteria that take into account the impacts of regulation on the biotic components of the river ecosystem. High resolution 2D spatial modelling of river habitats and floodplains is a powerful tool to make quantitative impact assessments of the biota. Physical variables commonly used in habitat models include depth, velocity and substrate size. In addition, other abiotic variables such as windgenerated wave stress, light penetration, water temperature, sedimentation of fine particles, specific discharge and bottom slope, that define the local 'hydroperiod' have been suggested. Our proposed approach integrates abiotic data obtained from numerical models, field measurements and biological information to overcome problems inherent in temporally and spatially heterogeneous river systems. This approach was tested with a habitat model applied to submerged aquatic vegetation, various categories of wetlands, benthic organisms and various life stages of a number of fish species. Logistic regression is the statistical model currently used to synthesize the relationships between abiotic and biotic factors. The short-term objective of this modelling exercise in the St. Lawrence River is to understand the underlying links 2 Revue canadienne des ressources hydriques Vol. 28, No. 2, 2003 between fluvial physics and biota. A longer-term objective is to provide a real-time analysis of key variables and to quantify the links between trophic levels.
Limnology and oceanography, methods
Cross-sectional gradients in water levels and velocities play a determining role in the circulati... more Cross-sectional gradients in water levels and velocities play a determining role in the circulation dynamics of tidal rivers and estuaries. Documenting and analyzing their variability throughout a tidal cycle require observations with high spatial and temporal resolution. A survey strategy and a data analysis procedure have been designed to obtain continuous and synoptic water level and velocity fields over a tidal cycle, along 13 cross-sections of the St. Lawrence fluvial estuary dominated by large tidal ranges. The method combines both RTK GPS and ADCP technologies for the simultaneous measurement of water levels and velocities along repeated boat transects, allowing fast data acquisition over wide river sections and under rapidly changing conditions. The reconstruction of continuous and synoptic fields is made by interpolation. Simplifying assumptions about data stationarity and/or homogeneity are avoided by adapting the interpolation procedures to the shape and distribution of t...
Journal of Great Lakes Research, 2000
Lake Saint-François is a fluvial lake of the St. Lawrence system which is used for hydropower pro... more Lake Saint-François is a fluvial lake of the St. Lawrence system which is used for hydropower production and commercial navigation. For 150 years, it was dredged and dammed regularly without any impact analysis being made. The cumulative impact of dredging and damming on large rivers such as the St. Lawrence is an issue with only qualitative answers. Bidimensional hydrodynamics was used to simulate ancient flow conditions and to produce quantitative descriptors. Two Numerical Field Models (NFM) were prepared, one representing present state geometry, which contains 300,000 sounding points, and the other representing pristine state, based on 1900 and 1870 measurements and containing 70,000 soundings. These two NFMs were compared, showing important changes in the morphology of the lake. The NFMs were then used for bidimensional hydrodynamic simulations of both actual and pristine states for 3 different discharges: 5,000 m 3 /s, 7,500 m 3 /s, and 10,000 m 3 /s. Results highlight the cumulative physical transformation of the system. Hydrodynamic simulations and velocity differences show an increase of velocities over shoals for discharge under 8,800 m 3 /s, and a decrease of velocities in deeper water for the same range of discharge. Dredging and straightening around Cornwall Island resulted in changes from 64% to 71% of the total river flow passing through the south channel while the flow in the north channel decreased from 36% to 29%. These hydrodynamic transformations had a definitive impact on sedimentation and most probably on aquatic plant distribution.
River Research and Applications, 2013
A daily averaged two-dimensional water temperature model has been developed for the freshwater pa... more A daily averaged two-dimensional water temperature model has been developed for the freshwater part of the St. Lawrence River, between Lake St. Louis and Trois-Rivières (Québec, Canada). The model was first calibrated and validated for the area of Lake St. Pierre, a natural enlargement of the river subject to strong lateral and longitudinal thermal variations. Forecasts from the Global Environmental Multiscale model were used in preference to observations from meteorological stations for model inputs, both to increase the spatial resolution and ultimately to allow the water temperature model to be used in predictive mode. The resulting model provided daily water temperature estimates with an overall root mean square error (RMSE) of 1.18 C and a Nash-Sutcliffe coefficient of 0.44. Comparisons between Landsat images and simulations demonstrated that the model not only simulated accurate water temperature values but also showed the adequacy of the model in general. It not only simulated local water temperature relatively accurately but also provided a good representation of the spatial water temperature patterns within the study area. The error varied between deep and shallow water areas. In deeper water, the overall RMSE is 0.41 C, and the modified Nash coefficient rises up to 0.92. Because shallow water areas are subject to greater variations, longer, more spatially dense data sets will be needed to refine the hydrodynamic and thermal budget models for those specific areas.
Journal of Atmospheric and Oceanic Technology, 2014
Measuring temporal and spatial variations in water level with high resolution and accuracy can pr... more Measuring temporal and spatial variations in water level with high resolution and accuracy can provide fundamental insights into the hydrodynamics of marine and riverine systems. Real-time kinematic global positioning systems (RTK GPS), and by extension postprocessed kinematic (PPK) positioning, have provided the opportunity to achieve this goal, by allowing fast and straightforward measurements with subdecimeter accuracy. However, boat-mounted GPS are subject to movements of the water surface (e.g., waves, longperiod heaves) as well as to the effects of dynamic draft. The latter contaminate the records and need to be separated and removed from the data. A method is proposed to postcorrect the elevation data using tilt information measured by an attitude sensor-in this case, an acoustic Doppler current profiler (ADCP) equipped with internal pitch and roll sensors. The technique uses iteratively reweighted least squares (IRLS) regressions to determine the position of the center of rotation (COR) of the boat that leads to optimal corrections. The COR is also allowed to change in time by performing the IRLS analyses on data subsamples, thus accounting for changes in weight distribution, for example, due to personnel movements. An example of application is presented using data collected in the Saint Lawrence fluvial estuary. The corrections exhibit significant reductions associated with the boat motion while keeping subtle variations in water levels likely related to local hydrodynamics.
Canadian Water Resources Journal, 2003
The St. Lawrence River is one of the most important large rivers in North America. This 600-km lo... more The St. Lawrence River is one of the most important large rivers in North America. This 600-km long watercourse is characterized by a high degree of physical heterogeneity, including fast moving narrow reaches separated by fluvial lakes reaching 10 km in width. The mean annual discharge from the outflow of Lake Ontario is 7500 m 3 /s and has been managed for hydropower and transportation since the 1960s. With the management plan currently under review an effort is being made to include criteria that take into account the impacts of regulation on the biotic components of the river ecosystem. High resolution 2D spatial modelling of river habitats and floodplains is a powerful tool to make quantitative impact assessments of the biota. Physical variables commonly used in habitat models include depth, velocity and substrate size. In addition, other abiotic variables such as windgenerated wave stress, light penetration, water temperature, sedimentation of fine particles, specific discharge and bottom slope, that define the local 'hydroperiod' have been suggested. Our proposed approach integrates abiotic data obtained from numerical models, field measurements and biological information to overcome problems inherent in temporally and spatially heterogeneous river systems. This approach was tested with a habitat model applied to submerged aquatic vegetation, various categories of wetlands, benthic organisms and various life stages of a number of fish species. Logistic regression is the statistical model currently used to synthesize the relationships between abiotic and biotic factors. The short-term objective of this modelling exercise in the St. Lawrence River is to understand the underlying links 2 Revue canadienne des ressources hydriques Vol. 28, No. 2, 2003 between fluvial physics and biota. A longer-term objective is to provide a real-time analysis of key variables and to quantify the links between trophic levels.
Hydrological Processes, 2014
One of the challenges when modelling a complex variable such as water temperature in rivers is th... more One of the challenges when modelling a complex variable such as water temperature in rivers is that it can be difficult to determine the sources of error and to ensure that the simulations are truly representative of the reality. Therefore, a heat budget study was completed in a controlled environment, which excluded advection and bottom fluxes but enabled observation of all the other fluxes. A 21.42 m 3 pool was installed and insulated to limit heat exchange through the sides and bottom. All the major energy fluxes were monitored for a 50-day period. Different equations for individual heat budget terms were tested to determine their ability to reproduce the observations. This experiment also permitted to assess the relative importance of each component of the heat budget. Performance of each semiempirical equation was determined by comparing predictions and measured values. It was thus possible to choose the formulae that best represented the measured heat exchange processes, while understanding the limits of some of the semi-empirical representations of heat exchange processes. The results highlight the importance of radiative terms into the heat budget because they controlled the major sources and sinks. The study also showed the importance of the wind function determination into the calculation of latent heat flux. The resulting water temperature model returned simulated hourly water temperature with an overall root mean square error of 0.71 C/h and a modified Nash-Sutcliffe coefficient of 0.97.
Journal of Geophysical Research: Oceans, 2014
Predicting tides in upstream reaches of rivers is a challenge, because tides are highly nonlinear... more Predicting tides in upstream reaches of rivers is a challenge, because tides are highly nonlinear and nonstationary, and accurate short-time predictions of river flow are hard to obtain. In the St. Lawrence fluvial estuary, tide forecasts are produced using a one-dimensional model (ONE-D), forced downstream with harmonic constituents, and upstream with daily discharges using 30 day flow forecasts from Lake Ontario and the Ottawa River. Although this operational forecast system serves its purpose of predicting water levels, information about nonstationary tidal-fluvial processes that can be gained from it is limited, particularly the temporal changes in mean water level and tidal properties (i.e., constituent amplitudes and phases), which are function of river flow and ocean tidal range. In this paper, a harmonic model adapted to nonstationary tides, NS_TIDE, was applied to the St. Lawrence fluvial estuary, where the time-varying external forcing is directly built into the tidal basis functions. Model coefficients from 13 analysis stations were spatially interpolated to allow tide predictions at arbitrary locations as well as to provide insights into the spatiotemporal evolution of tides. Model hindcasts showed substantial improvements compared to classical harmonic analyses at upstream stations. The model was further validated by comparison with ONE-D predictions at a total of 32 stations. The slightly lower accuracy obtained with NS_TIDE is compensated by model simplicity, efficiency, and capacity to represent stage and tidal variations in a very compact way and thus represents a new means for understanding tidal rivers.
Revue européenne des éléments finis
Revue européenne des éléments finis, 2005
ABSTRACT La validation par les vitesses d’un modèle hydrodynamique montre que la variabilité du p... more ABSTRACT La validation par les vitesses d’un modèle hydrodynamique montre que la variabilité du profil vertical des vitesses a une influence importante sur le résultat. Ici, cette variabilité a été introduite sous la forme d’un terme de dispersion dans un modèle hydrodynamique qui résout les équations de Saint-Venant 2D par la méthode des éléments finis. Nous tentons ensuite de la représenter à l’aide des variables du modèle (u, v, h). Le modèle appliqué à un canal courbe de 270° montre que la variabilité spatiale de la distribution des vitesses est améliorée, que ce soit par la prise en compte de la variabilité mesurée ou par le paramétrage de celle-ci. Une application est effectuée sur la rivière des Escoumins, petit cours d’eau alluvionnaire à la topographie complexe. Les résultats montrent que la modification du modèle de Saint-Venant améliore la description de l’écoulement mais ne suffit pas à représenter correctement celui-ci.
Anais da Academia Brasileira de Ciencias, 2015
In Belém city is located the potable water supply system of its metropolitan area, which includes... more In Belém city is located the potable water supply system of its metropolitan area, which includes, in addition to this city, four more municipalities. In this water supply complex is the Água Preta lake, which serves as a reservoir for the water pumped from the Guamá river. Due to the great importance of this lake for this system, several works have been devoted to its study, from the monitoring of the quality of its waters to its hydrodynamic modeling. This paper presents the results obtained by computer simulation of the phosphorus dispersion within this reservoir by the numerical solution of two-dimensional equation of advection-diffusion-reaction by the method θ/SUPG. Comparing these results with data concentration of total phosphorus collected from November 2008 to October 2009 and from satellite photos show that the biggest polluters of the water of this lake are the domestic sewage dumps from the population living in its vicinity. The results obtained indicate the need for mo...
Brazil’s has a vast and dense hydrographic network. In Para state’s Tucuruí municipality, about 3... more Brazil’s has a vast and dense hydrographic network. In Para state’s Tucuruí municipality, about 300 km south of Belem, there’s a hydroelectric central which is considered large – the UHE Tucuruí located on Tocantins River. Study area of this current work is restricted to a stretch of Tocantins River starting from the UHE Tucuruí downstream until Tucuruí city. The flow has been modeled for the evaluation of sites where hydrokinetic turbines can be installed to take advantage of UHE Tucuruí remaining potentials. This potential can be used to supply communities still isolated in the region. This study guides on the hydrodynamic modeling of the stretch mentioned above, starting from bathymetric data collecting and substrate composition, elaboration of terrain’s elevation model and substrate model. Hydrodynamic simulations are established by the Saint-Venant Model. Modeling results, i.e., velocities and depths analyzed in the study area, serve to the evaluation and determination of sites...
Na Amazônia, o potencial hidrelétrico pode ser estimado somente nas grandes bacias, pois são as ú... more Na Amazônia, o potencial hidrelétrico pode ser estimado somente nas grandes bacias, pois são as únicas que possuem dados de vazão. Tal fato deixa de lado inúmeras pequenas bacias que poderiam atender às pequenas comunidades isoladas através da implantação de microcentrais hidrelétricas. Os dados comumente disponíveis na região são os pluviométricos. Assim, o objetivo principal deste artigo é a aplicação e a transposição de um modelo chuva-vazão visando à simulação de curvas de permanência. A simulação das vazões é formulada a partir de um sistema linear (entrada-saída) invariável no tempo. O modelo é aplicado a duas pequenas bacias localizadas no Estado do Pará. Uma análise de sensibilidade do modelo, em função do tamanho das amostras de chuva e vazão, é efetuada com o objetivo de determinar o período de dados mais curto que ainda assegure uma boa aplicação do modelo. Como se tem duas pequenas bacias, é efetuada a transposição do modelo e uma análise de sensibilidade em função do ta...
Canadian Water Resources Journal, 2003
The St. Lawrence River is one of the most important large rivers in North America. This 600-km lo... more The St. Lawrence River is one of the most important large rivers in North America. This 600-km long watercourse is characterized by a high degree of physical heterogeneity, including fast moving narrow reaches separated by fluvial lakes reaching 10 km in width. The mean annual discharge from the outflow of Lake Ontario is 7500 m 3 /s and has been managed for hydropower and transportation since the 1960s. With the management plan currently under review an effort is being made to include criteria that take into account the impacts of regulation on the biotic components of the river ecosystem. High resolution 2D spatial modelling of river habitats and floodplains is a powerful tool to make quantitative impact assessments of the biota. Physical variables commonly used in habitat models include depth, velocity and substrate size. In addition, other abiotic variables such as windgenerated wave stress, light penetration, water temperature, sedimentation of fine particles, specific discharge and bottom slope, that define the local 'hydroperiod' have been suggested. Our proposed approach integrates abiotic data obtained from numerical models, field measurements and biological information to overcome problems inherent in temporally and spatially heterogeneous river systems. This approach was tested with a habitat model applied to submerged aquatic vegetation, various categories of wetlands, benthic organisms and various life stages of a number of fish species. Logistic regression is the statistical model currently used to synthesize the relationships between abiotic and biotic factors. The short-term objective of this modelling exercise in the St. Lawrence River is to understand the underlying links 2 Revue canadienne des ressources hydriques Vol. 28, No. 2, 2003 between fluvial physics and biota. A longer-term objective is to provide a real-time analysis of key variables and to quantify the links between trophic levels.
Limnology and oceanography, methods
Cross-sectional gradients in water levels and velocities play a determining role in the circulati... more Cross-sectional gradients in water levels and velocities play a determining role in the circulation dynamics of tidal rivers and estuaries. Documenting and analyzing their variability throughout a tidal cycle require observations with high spatial and temporal resolution. A survey strategy and a data analysis procedure have been designed to obtain continuous and synoptic water level and velocity fields over a tidal cycle, along 13 cross-sections of the St. Lawrence fluvial estuary dominated by large tidal ranges. The method combines both RTK GPS and ADCP technologies for the simultaneous measurement of water levels and velocities along repeated boat transects, allowing fast data acquisition over wide river sections and under rapidly changing conditions. The reconstruction of continuous and synoptic fields is made by interpolation. Simplifying assumptions about data stationarity and/or homogeneity are avoided by adapting the interpolation procedures to the shape and distribution of t...
Journal of Great Lakes Research, 2000
Lake Saint-François is a fluvial lake of the St. Lawrence system which is used for hydropower pro... more Lake Saint-François is a fluvial lake of the St. Lawrence system which is used for hydropower production and commercial navigation. For 150 years, it was dredged and dammed regularly without any impact analysis being made. The cumulative impact of dredging and damming on large rivers such as the St. Lawrence is an issue with only qualitative answers. Bidimensional hydrodynamics was used to simulate ancient flow conditions and to produce quantitative descriptors. Two Numerical Field Models (NFM) were prepared, one representing present state geometry, which contains 300,000 sounding points, and the other representing pristine state, based on 1900 and 1870 measurements and containing 70,000 soundings. These two NFMs were compared, showing important changes in the morphology of the lake. The NFMs were then used for bidimensional hydrodynamic simulations of both actual and pristine states for 3 different discharges: 5,000 m 3 /s, 7,500 m 3 /s, and 10,000 m 3 /s. Results highlight the cumulative physical transformation of the system. Hydrodynamic simulations and velocity differences show an increase of velocities over shoals for discharge under 8,800 m 3 /s, and a decrease of velocities in deeper water for the same range of discharge. Dredging and straightening around Cornwall Island resulted in changes from 64% to 71% of the total river flow passing through the south channel while the flow in the north channel decreased from 36% to 29%. These hydrodynamic transformations had a definitive impact on sedimentation and most probably on aquatic plant distribution.
River Research and Applications, 2013
A daily averaged two-dimensional water temperature model has been developed for the freshwater pa... more A daily averaged two-dimensional water temperature model has been developed for the freshwater part of the St. Lawrence River, between Lake St. Louis and Trois-Rivières (Québec, Canada). The model was first calibrated and validated for the area of Lake St. Pierre, a natural enlargement of the river subject to strong lateral and longitudinal thermal variations. Forecasts from the Global Environmental Multiscale model were used in preference to observations from meteorological stations for model inputs, both to increase the spatial resolution and ultimately to allow the water temperature model to be used in predictive mode. The resulting model provided daily water temperature estimates with an overall root mean square error (RMSE) of 1.18 C and a Nash-Sutcliffe coefficient of 0.44. Comparisons between Landsat images and simulations demonstrated that the model not only simulated accurate water temperature values but also showed the adequacy of the model in general. It not only simulated local water temperature relatively accurately but also provided a good representation of the spatial water temperature patterns within the study area. The error varied between deep and shallow water areas. In deeper water, the overall RMSE is 0.41 C, and the modified Nash coefficient rises up to 0.92. Because shallow water areas are subject to greater variations, longer, more spatially dense data sets will be needed to refine the hydrodynamic and thermal budget models for those specific areas.
Journal of Atmospheric and Oceanic Technology, 2014
Measuring temporal and spatial variations in water level with high resolution and accuracy can pr... more Measuring temporal and spatial variations in water level with high resolution and accuracy can provide fundamental insights into the hydrodynamics of marine and riverine systems. Real-time kinematic global positioning systems (RTK GPS), and by extension postprocessed kinematic (PPK) positioning, have provided the opportunity to achieve this goal, by allowing fast and straightforward measurements with subdecimeter accuracy. However, boat-mounted GPS are subject to movements of the water surface (e.g., waves, longperiod heaves) as well as to the effects of dynamic draft. The latter contaminate the records and need to be separated and removed from the data. A method is proposed to postcorrect the elevation data using tilt information measured by an attitude sensor-in this case, an acoustic Doppler current profiler (ADCP) equipped with internal pitch and roll sensors. The technique uses iteratively reweighted least squares (IRLS) regressions to determine the position of the center of rotation (COR) of the boat that leads to optimal corrections. The COR is also allowed to change in time by performing the IRLS analyses on data subsamples, thus accounting for changes in weight distribution, for example, due to personnel movements. An example of application is presented using data collected in the Saint Lawrence fluvial estuary. The corrections exhibit significant reductions associated with the boat motion while keeping subtle variations in water levels likely related to local hydrodynamics.
Canadian Water Resources Journal, 2003
The St. Lawrence River is one of the most important large rivers in North America. This 600-km lo... more The St. Lawrence River is one of the most important large rivers in North America. This 600-km long watercourse is characterized by a high degree of physical heterogeneity, including fast moving narrow reaches separated by fluvial lakes reaching 10 km in width. The mean annual discharge from the outflow of Lake Ontario is 7500 m 3 /s and has been managed for hydropower and transportation since the 1960s. With the management plan currently under review an effort is being made to include criteria that take into account the impacts of regulation on the biotic components of the river ecosystem. High resolution 2D spatial modelling of river habitats and floodplains is a powerful tool to make quantitative impact assessments of the biota. Physical variables commonly used in habitat models include depth, velocity and substrate size. In addition, other abiotic variables such as windgenerated wave stress, light penetration, water temperature, sedimentation of fine particles, specific discharge and bottom slope, that define the local 'hydroperiod' have been suggested. Our proposed approach integrates abiotic data obtained from numerical models, field measurements and biological information to overcome problems inherent in temporally and spatially heterogeneous river systems. This approach was tested with a habitat model applied to submerged aquatic vegetation, various categories of wetlands, benthic organisms and various life stages of a number of fish species. Logistic regression is the statistical model currently used to synthesize the relationships between abiotic and biotic factors. The short-term objective of this modelling exercise in the St. Lawrence River is to understand the underlying links 2 Revue canadienne des ressources hydriques Vol. 28, No. 2, 2003 between fluvial physics and biota. A longer-term objective is to provide a real-time analysis of key variables and to quantify the links between trophic levels.
Hydrological Processes, 2014
One of the challenges when modelling a complex variable such as water temperature in rivers is th... more One of the challenges when modelling a complex variable such as water temperature in rivers is that it can be difficult to determine the sources of error and to ensure that the simulations are truly representative of the reality. Therefore, a heat budget study was completed in a controlled environment, which excluded advection and bottom fluxes but enabled observation of all the other fluxes. A 21.42 m 3 pool was installed and insulated to limit heat exchange through the sides and bottom. All the major energy fluxes were monitored for a 50-day period. Different equations for individual heat budget terms were tested to determine their ability to reproduce the observations. This experiment also permitted to assess the relative importance of each component of the heat budget. Performance of each semiempirical equation was determined by comparing predictions and measured values. It was thus possible to choose the formulae that best represented the measured heat exchange processes, while understanding the limits of some of the semi-empirical representations of heat exchange processes. The results highlight the importance of radiative terms into the heat budget because they controlled the major sources and sinks. The study also showed the importance of the wind function determination into the calculation of latent heat flux. The resulting water temperature model returned simulated hourly water temperature with an overall root mean square error of 0.71 C/h and a modified Nash-Sutcliffe coefficient of 0.97.
Journal of Geophysical Research: Oceans, 2014
Predicting tides in upstream reaches of rivers is a challenge, because tides are highly nonlinear... more Predicting tides in upstream reaches of rivers is a challenge, because tides are highly nonlinear and nonstationary, and accurate short-time predictions of river flow are hard to obtain. In the St. Lawrence fluvial estuary, tide forecasts are produced using a one-dimensional model (ONE-D), forced downstream with harmonic constituents, and upstream with daily discharges using 30 day flow forecasts from Lake Ontario and the Ottawa River. Although this operational forecast system serves its purpose of predicting water levels, information about nonstationary tidal-fluvial processes that can be gained from it is limited, particularly the temporal changes in mean water level and tidal properties (i.e., constituent amplitudes and phases), which are function of river flow and ocean tidal range. In this paper, a harmonic model adapted to nonstationary tides, NS_TIDE, was applied to the St. Lawrence fluvial estuary, where the time-varying external forcing is directly built into the tidal basis functions. Model coefficients from 13 analysis stations were spatially interpolated to allow tide predictions at arbitrary locations as well as to provide insights into the spatiotemporal evolution of tides. Model hindcasts showed substantial improvements compared to classical harmonic analyses at upstream stations. The model was further validated by comparison with ONE-D predictions at a total of 32 stations. The slightly lower accuracy obtained with NS_TIDE is compensated by model simplicity, efficiency, and capacity to represent stage and tidal variations in a very compact way and thus represents a new means for understanding tidal rivers.
Revue européenne des éléments finis
Revue européenne des éléments finis, 2005
ABSTRACT La validation par les vitesses d’un modèle hydrodynamique montre que la variabilité du p... more ABSTRACT La validation par les vitesses d’un modèle hydrodynamique montre que la variabilité du profil vertical des vitesses a une influence importante sur le résultat. Ici, cette variabilité a été introduite sous la forme d’un terme de dispersion dans un modèle hydrodynamique qui résout les équations de Saint-Venant 2D par la méthode des éléments finis. Nous tentons ensuite de la représenter à l’aide des variables du modèle (u, v, h). Le modèle appliqué à un canal courbe de 270° montre que la variabilité spatiale de la distribution des vitesses est améliorée, que ce soit par la prise en compte de la variabilité mesurée ou par le paramétrage de celle-ci. Une application est effectuée sur la rivière des Escoumins, petit cours d’eau alluvionnaire à la topographie complexe. Les résultats montrent que la modification du modèle de Saint-Venant améliore la description de l’écoulement mais ne suffit pas à représenter correctement celui-ci.
Anais da Academia Brasileira de Ciencias, 2015
In Belém city is located the potable water supply system of its metropolitan area, which includes... more In Belém city is located the potable water supply system of its metropolitan area, which includes, in addition to this city, four more municipalities. In this water supply complex is the Água Preta lake, which serves as a reservoir for the water pumped from the Guamá river. Due to the great importance of this lake for this system, several works have been devoted to its study, from the monitoring of the quality of its waters to its hydrodynamic modeling. This paper presents the results obtained by computer simulation of the phosphorus dispersion within this reservoir by the numerical solution of two-dimensional equation of advection-diffusion-reaction by the method θ/SUPG. Comparing these results with data concentration of total phosphorus collected from November 2008 to October 2009 and from satellite photos show that the biggest polluters of the water of this lake are the domestic sewage dumps from the population living in its vicinity. The results obtained indicate the need for mo...
Brazil’s has a vast and dense hydrographic network. In Para state’s Tucuruí municipality, about 3... more Brazil’s has a vast and dense hydrographic network. In Para state’s Tucuruí municipality, about 300 km south of Belem, there’s a hydroelectric central which is considered large – the UHE Tucuruí located on Tocantins River. Study area of this current work is restricted to a stretch of Tocantins River starting from the UHE Tucuruí downstream until Tucuruí city. The flow has been modeled for the evaluation of sites where hydrokinetic turbines can be installed to take advantage of UHE Tucuruí remaining potentials. This potential can be used to supply communities still isolated in the region. This study guides on the hydrodynamic modeling of the stretch mentioned above, starting from bathymetric data collecting and substrate composition, elaboration of terrain’s elevation model and substrate model. Hydrodynamic simulations are established by the Saint-Venant Model. Modeling results, i.e., velocities and depths analyzed in the study area, serve to the evaluation and determination of sites...
Na Amazônia, o potencial hidrelétrico pode ser estimado somente nas grandes bacias, pois são as ú... more Na Amazônia, o potencial hidrelétrico pode ser estimado somente nas grandes bacias, pois são as únicas que possuem dados de vazão. Tal fato deixa de lado inúmeras pequenas bacias que poderiam atender às pequenas comunidades isoladas através da implantação de microcentrais hidrelétricas. Os dados comumente disponíveis na região são os pluviométricos. Assim, o objetivo principal deste artigo é a aplicação e a transposição de um modelo chuva-vazão visando à simulação de curvas de permanência. A simulação das vazões é formulada a partir de um sistema linear (entrada-saída) invariável no tempo. O modelo é aplicado a duas pequenas bacias localizadas no Estado do Pará. Uma análise de sensibilidade do modelo, em função do tamanho das amostras de chuva e vazão, é efetuada com o objetivo de determinar o período de dados mais curto que ainda assegure uma boa aplicação do modelo. Como se tem duas pequenas bacias, é efetuada a transposição do modelo e uma análise de sensibilidade em função do ta...
River Research and Applications, 2013
A daily averaged two-dimensional water temperature model has been developed for the freshwater pa... more A daily averaged two-dimensional water temperature model has been developed for the freshwater part of the St. Lawrence River, between Lake St. Louis and Trois-Rivières (Québec, Canada). The model was first calibrated and validated for the area of Lake St. Pierre, a natural enlargement of the river subject to strong lateral and longitudinal thermal variations. Forecasts from the Global Environmental Multiscale model were used in preference to observations from meteorological stations for model inputs, both to increase the spatial resolution and ultimately to allow the water temperature model to be used in predictive mode. The resulting model provided daily water temperature estimates with an overall root mean square error (RMSE) of 1.18 C and a Nash-Sutcliffe coefficient of 0.44. Comparisons between Landsat images and simulations demonstrated that the model not only simulated accurate water temperature values but also showed the adequacy of the model in general. It not only simulated local water temperature relatively accurately but also provided a good representation of the spatial water temperature patterns within the study area. The error varied between deep and shallow water areas. In deeper water, the overall RMSE is 0.41 C, and the modified Nash coefficient rises up to 0.92. Because shallow water areas are subject to greater variations, longer, more spatially dense data sets will be needed to refine the hydrodynamic and thermal budget models for those specific areas.
A discussion of the modular program Mikado is presented. Mikado was developed with the goal of cr... more A discussion of the modular program Mikado is presented. Mikado was developed with the goal of creating a flexible graphic tool to display and help analyze the results of finite element fluid flow computations. Mikado works on unstructured meshes, with elements of mixed geometric type, but also offers the possibility of using structured meshes. The program can be operated by both menu and mouse (interactive), or by command file (batch). Mikado is written in FORTRAN, except for a few system dependent subroutines which are in C. It runs presently on Silicon Graphics' workstations and could be easily ported to the IBM-RISC System/6000 family of workstations.