Total Suspended Sediment

Une base de données numériques d'états de mer en Méditerranée est en cours de construction à partir de simulations effectuées avec le logiciel de TOMAWAC sur la période 1979-2008 afin de venir compléter l'actuelle base de donnée ANEMOC couvrant la façade Atlantique-Manche-Mer du Nord des côtes françaises. Les champs de vent utilisés en entrée sont issus de la réanalyse météorologique NCEP2 du U.S. Climate Diagnostics Center of the National Oceanic and Atmospheric Administration (CDC-NOAA). Les résultats du modèle sont comparés à des mesures de bouées et des mesures satellitaires altimétriques. Les premières comparaisons des résultats de simulations aux mesures montrent un biais moyen négatif (sous-estimation) de la hauteur significative d'état de mer, qu'il convient d'améliorer en travaillant sur les champs de vent et en ajustant les paramètres physiques des termes puits / sources du modèle d'états de mer.

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light e...

Cetteétude analyse la sensibilité d'un modèle hydrodynamique de maréeà la paramétrisation de la rugosité des fonds rocheux au niveau du Passage du Fromveur en pointe Bretagne. L'attention est portée sur les estimations des courants, de la puissance associée et de la contrainte de cisaillement de fond sans et avec la présence d'un parc hydrolien. Les prédictions de la puissance du courant disponible présentent des variations allant jusqu'à 30 % en fonction de la rugosité de fond retenue. L'extraction de cette puissance par un parc hydrolien induit une réduction substantielle des courants de marée et de la contrainte de cisaillement de fond associéeà plus de 10 km du Passage du Fromveur. La rugosité de fond influe sur l'amplitude de cette réduction avec des variations de la contrainte de cisaillement comprises entre 9 et 17 % au niveau du banc sableux du Four.

Water quality in the Paso Piedras Reservoir has deteriorated, primarily due to periodic blue-green algal blooms, making it temporarily unfit for human consumption. This phenomenon results from the eutrophication of waters of the watershed, and nutrients are considered to be the primary contributors to degradation of freshwater quality. In order to reduce the levels of nitrogen and, most of all, phosphorus, entering the Paso Piedras Reservoir, it is necessary to understand the incidence of diffuse transfers of nutrients from agricultural soils. The nitrogen composition, soluble reactive phosphorus (SRP) and other physico-chemical parameters of the water were analysed in various different parts of the watershed in order to characterize water input to the reservoir from areas with different anthropogenic activity. The upper Sauce Grande basin was divided into three areas with different edaphic characteristics. The physico-chemical parameters measured in sampling surveys included: SRP, ammonium and nitrate, pH, conductivity, turbidity, and total solids. The results showed that the water of the Sauce Grande (areas 1 and 2) was not strongly contaminated, but in El Divisorio (Area 3, which is a sub-watershed whose stream flows directly into the Paso Piedras Reservoir), the levels of conductivity, total suspended sediments and SRP were so high that its contribution to the reservoir accounts for nearly 50% of the total SRP input. The main characteristics of El Divisorio watershed that make it a diffuse source of SRP were not only that its soils, under agriculturallivestock production, have significant slopes, so that water and wind erosion are faster, but also that human intervention had caused the destruction of aggregates. The results showed the influence of the soil characteristics, production systems and the micro-environment developed in the reservoir on the characteristics of waters flowing out of the reservoir. The two villages located in Area 2 had no significant influence on the concentration of nitrogen compounds and SRP found downstream.

This study describes the geochemistry of dissolved elements in the Caura River and gives information about weathering rates and associated CO2 consumption in an Orinoco River subbasin. Physicochemical variables (pH, conductivity, HCO3−, dissolved O2, and temperature), dissolved elements (Na, K, Ca, Mg, Si, Al, Fe, Cu, Mn, Zn, and Cr), total suspended sediments (TSS), and dissolved organic carbon (DOC) concentrations were measured monthly from June 2007 to August 2008 in the Caura River. Major element concentrations (Na, Ca, Mg, and Si) showed an inverse correlation with discharge, whereas K showed high concentration values during the rising waters, probably due to biogenic sources. All these elements are provided mainly from weathering of plagioclases and K feldspars. The weathering rate (riverine flux of dissolved major cations and SiO2 derived from weathering per unit area) and the CO2 consumption rate in the Caura basin (15.4 tons km−2 yr−1 and 1.1 × 105 mol km−2 yr−1, respective...

A three-dimensional (3-D) suspended sediment model was coupled with a 3-D hydrodynamic numerical model and used to examine the spatial and temporal distribution of suspended sediments in the Satilla River estuary of Georgia. The hydrodynamic model was a modified ECOM-si model with inclusion of the flooding-drying cycle over intertidal salt marshes. The suspended sediment model consisted of a simple passive tracer equation with inclusion of sinking, resuspension, and sedimentation processes. The coupled model was driven by tidal forcing at the open boundary over the inner shelf of the South Atlantic Bight and real-time river discharge at the upstream end of the estuary, with a uniform initial distribution of total suspended sediment (TSS). The initial conditions for salinity were specified using observations taken along the estuary. The coupled model provided a reasonable simulation of both the spatial and temporal distributions of observed TSS concentration. Model-predicted TSS concentrations varied over a tidal cycle; they were highest at maximum flood and ebb tidal phases and lowest at slack tides. Model-guided process studies suggest that the spatial distribution of TSS concentration in the Satilla River estuary is controlled by a complex nonlinear physical process associated with the convergence and divergence of residual flow, a non-uniform along-estuary distribution of bottom stress, and the inertial effects of a curved shoreline.

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light e...

The objective of this research study was to assess the potential of remotely sensed data for estimation of water quality parameters in water bodies. The assessment was based on the field measurements, laboratory examination and data analysis of the collected hyperspectral reflectance data. The factors influencing the qualitative and quantitative nature of the spectra were also analyzed. The hyperspectral data is integrated into ALOS/AVNIR-2 band widths. Examination and correlation of simulated ALOS data reveals that multiplicative two band approach by using Band 4 (NIR) and Band 3 (Red) is best predictor of suspended sediments in water bodies. The ratio of ALOS/AVNIR-2 Band 3 and Band 1 was most closely correlated with Chl-a concentration. For estimation of total suspended sediments (TSS), a higher accuracy was achieved using the Band 4 /Band 2 ratios. Color dissolved organic matters (CDOM) were found to be well correlated with Band 1/Band 2. Regression models were developed and the...

La maintenance des chenaux de navigation et des zones portuaires implique la réalisation d'opérations de dragage pour garantir une profondeur d'eau suffisante. Les produits de dragages sont déposés en mer (opération de clapage) si les conditions d'immersion fixées par la convention d'Oslo sont satisfaites. Toutefois, le clapage de sédiments peut induire des nuisances sur l'environnement. Nous utilisons un modèle de transport sédimentaire à deux phases que nous avons développé (BARBRY et al., 2000 ; NGUYEN et al., 2009 ; CHAUCHAT et al., 2008) pour simuler le phénomène de clapage de sédiment fin. La comparaison des simulations aux résultats expérimentaux réalisés en canal par BOUTIN (2000), VILLARET et al. (1997) et VILLARET et al. (1998) montre le bon comportement du modèle pour décrire les différentes phases dynamiques de ce phénomène.

Available secondary suspended sediment data from the 1980s was analyzed together with new data collected during 2001-2003 at instrumented sites upstream and downstream of open-cast mining activities ($4.2 km 2) in an enclosure within the Kudremukh National Park in south India. More than 50% of the suspended sediment load in both the Bhadra River and Bhadra Reservoir comes from mining-affected lands that occupy <1% of the total catchment area (1968 km 2). For baseflow conditions during the post-monsoon period of 2001, 0.02 Mg km À2 day À1 of suspended sediment was discharged at the upstream site compared with 0.74 Mg km À2 day À1 downstream of the mine. During the 2002 and 2003 monsoons, these rates increased to about 1.99 and 7.89 Mg km À2 day À1 for upstream and downstream sites, respectively. The specific sediment yield above the mine is 239 Mg km À2 year À1 versus 947 Mg km À2 year À1 downstream. Sediment concentration downstream was significantly higher than upstream for all conditions. The current annual suspended sediment load below the mine ranges from 100,000 to over 150,000 Mg, depending on the size and frequency of large rain events. During the 2002 and 2003 monsoon seasons, 20-30% of the total suspended sediment load during the sampling period of 67 and 123 days, respectively, was transported in one single day and over one-third of the total recorded suspended load is discharged in less than 4 days in each monsoon. Daily rainfall and maximum hourly rainfall intensity were reasonable predictors of daily sediment loads downstream of the mine (R 2 = 0.71 and 0.575, respectively; p < 0.001). However, the upstream response was not predicted well by these variables, suggesting an absence of rapid overland pathways and/or reduced availability of easily transportable sediment on the less-disturbed lands above the mining area. Large episodic sediment events downstream of the mine were associated with daily rainfall >150 mm and hourly intensities exceeding 20 mm. One hundred and nine such episodic events occurred between 1990 and 2001 alone. A conservative estimate of the total suspended sediment load in the Bhadra River after mining commenced in the 1980s is 1.37 Â 10 6 Mg, although the actual value could be considerably higher, up to 10 7 Mg. Comparison of historic data and another study in 1994, with recent measurements confirm that mining and associated activities in Kudremukh National Park are the greatest sources of sediment entering the Bhadra River; and the Bhadra river carries considerably more sediment now than before mining started damaging riverine ecosystems and disrupting downstream water resources.

In this study, an attempt has been made to evaluate the temporal variations in specific stream power and the total energy available for geomorphic work during the monsoon season for the Tapi River, in central India. Continuous daily discharge data (1978-1990), hydraulic geometry equations and the relationship between discharge and water surface slope were used to compute the daily specific stream power (ω) for the Savkheda gauging site in the lower Tapi Basin. The total amount of energy generated by all the monsoon flows was estimated by integrating the area under the ω-graph derived for the monsoon season. The analyses of the 13-year daily discharge data reveal that the average and maximum ω values range from 4-20 W m − 2 , and 22-964 W m − 2 respectively. Specific stream power duration curve derived for the site shows that for 25% of the time the power per unit area is N 10 W m − 2. Furthermore, unit stream power was found to be above the Williams' [Williams, G.P., 1983. Paleohydrological methods and some examples from Swedish fluvial environments. I. Cobble and boulder deposits. Geografiska Annaler 65A, 227-243.] threshold of pebble-movement (1.5 W m − 2), cobble-movement (16 W m − 2) and boulder-movement (90 W m − 2) for 71%, 15% and 2% of the time, respectively. Computations further indicate that the total amount of energy generated by the flows during the monsoon season is in the range of 37 MJ (deficit monsoon years) to 256 MJ (excess monsoon and/or flood years). Large floods have one-third share in the total monsoon energy expenditure. In the absence of appropriate data on the yearwise geomorphic effects, the geomorphic work was evaluated in terms of the total suspended sediment load transported. The total monsoon sediment load is strongly related to the total monsoon energy. The results of the study indicate that the average flow competence and capacity are remarkably higher during wetter monsoon seasons and flood years than during the shorter and drier monsoon seasons. The present analyses demonstrate that the flows are geomorphically effective for a greater part of the monsoon season, except during the deficient monsoon years, and there is little doubt that large-magnitude floods are effective agents of geomorphic change in monsoonal rivers.

Deposition of Hudson River sediment into New York Harbor interferes with navigation lanes and requires continuous dredging. Sediment dynamics at the Hudson estuary turbidity maximum (ETM) have received considerable study, but delivery of sediment to the ETM through the freshwater reach of the estuary has received relatively little attention and few direct measurements. An acoustic Doppler current profiler was positioned at the approximate limit of continuous freshwater to develop a 4-year time series of water velocity, discharge, suspended sediment concentration, and suspended sediment discharge. This data set was compared with suspended sediment discharge data collected during the same period at two sites just above the Hudson head-of-tide (the Federal Dam at Troy) that together represent the single largest source of sediment entering the estuary. The mean annual suspended sedimentdischarge from the freshwater reach of the estuary was 737,000 metric tons. Unexpectedly, the total suspended sediment discharge at the study site in November and December slightly exceeded that observed during March and April, the months during which rain and snowmelt typically result in the largest sediment discharge to the estuary. Suspended sediment discharge at the study site exceeded that from the Federal Dam, even though the intervening reach appears to store significant amounts of sediment, suggesting that 30-40% of sediment discharge observed at the study site is derived from tributaries to the estuary between the Federal Dam and study site. A simple model of sediment entering and passing through the freshwater reach on a timescale of weeks appears reasonable during normal hydrologic conditions in adjoining watersheds; however, this simple model may dramatically overestimate sediment delivery during extreme tributary high flows, especially those at the end of, or after, the "flushing season" (October through April). Previous estimates of annual or seasonal sediment delivery from tributaries and the Federal Dam to the ETM and harbor may be high for those years with extreme tributary highflow events.

The CANWET (Canadian ArcView Nutrient and Water Evaluation Tool) and HSPF (Hydrologic Simulation Program-FORTRAN) models were applied to Upper Canagagigue Creek watershed of the Grand River basin in southern Ontario, Canada, for hydrology and sediment evaluations. Both the models have similarity in structure where CANWET is simpler, both in algorithms and use, than HSPF. The outputs of both the models for water budgeting components were compared on annual, seasonal, and monthly basis. The water budget components, evapotranspiration, surface runoff, and subsurface runoff produced by both the models were comparable on annual and seasonal time steps; however, there were some discrepancies in monthly and daily simulations. The seasonal, monthly, and daily Nash-Sutcliffe efficiency coefficient with observed stream flows were 0.83, 0.81, and 0.48 for HSPF, respectively, and 0.80, 0.67, and 0.24 for CANWET, respectively. The monthly and daily simulations by HSPF model were better since HSPF algorithm has more control on temporal variation in parameters sensitive for hydrologic simulations. The sediment simulations by both the models were consistently close for erosion and sediment yield on annual basis. However, superiority in predictions for total suspended sediment yield of one model over the other could not be concluded because of lack of observed data. The daily load of sediment modeled by HSPF followed flow peaks and available observed sediment data points.

The CANWET (Canadian ArcView Nutrient and Water Evaluation Tool) and HSPF (Hydrologic Simulation Program-FORTRAN) models were applied to Upper Canagagigue Creek watershed of the Grand River basin in southern Ontario, Canada, for hydrology and sediment evaluations. Both the models have similarity in structure where CANWET is simpler, both in algorithms and use, than HSPF. The outputs of both the models for water budgeting components were compared on annual, seasonal, and monthly basis. The water budget components, evapotranspiration, surface runoff, and subsurface runoff produced by both the models were comparable on annual and seasonal time steps; however, there were some discrepancies in monthly and daily simulations. The seasonal, monthly, and daily Nash-Sutcliffe efficiency coefficient with observed stream flows were 0.83, 0.81, and 0.48 for HSPF, respectively, and 0.80, 0.67, and 0.24 for CANWET, respectively. The monthly and daily simulations by HSPF model were better since HSPF algorithm has more control on temporal variation in parameters sensitive for hydrologic simulations. The sediment simulations by both the models were consistently close for erosion and sediment yield on annual basis. However, superiority in predictions for total suspended sediment yield of one model over the other could not be concluded because of lack of observed data. The daily load of sediment modeled by HSPF followed flow peaks and available observed sediment data points.

The scope of this research was to study lake morphology using spatial simulation technique, to develop revised elevation-capacity curve, to develop elevation-water spread area curve, to study the relation between suspended sediment and remote sensing satellite data, and to estimate suspended sediment load in the lake using a Geographic Information System coupled with ground truth. The

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light e...

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light e...

A one-dimensional model of the vertical exchange of suspended sediment in a tidal boundary layer is proposed. The model includes two linearized momentum equations for the horizontal velocity components and a series of advection–diffusion equations for concentrations of suspended sediment of specific size. Turbulence generated at the sea-bed is computed with the aid of a two-equation closure describing the time–space

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light e...

This study describes the geochemistry of dissolved elements in the Caura River and gives information about weathering rates and associated CO 2 consumption in an Orinoco River subbasin. Physicochemical variables (pH, conductivity, HCO 3 − , dissolved O 2 , and temperature), dissolved elements (Na, K, Ca, Mg, Si, Al, Fe, Cu, Mn, Zn, and Cr), total suspended sediments (TSS), and dissolved organic carbon (DOC) concentrations were measured monthly from June 2007 to August 2008 in the Caura River. Major element concentrations (Na, Ca, Mg, and Si) showed an inverse correlation with discharge, whereas K showed high concentration values during the rising waters, probably due to biogenic sources. All these elements are provided mainly from weathering of plagioclases and K feldspars. The weathering rate (riverine flux of dissolved major cations and SiO 2 derived from weathering per unit area) and the CO 2 consumption rate in the Caura basin (15.4 tons km −2 yr −1 and 1.1 × 10 5 mol km −2 yr −1 , respectively) were higher than those reported for the Orinoco basin and other black water river basins. This fact can be due to several factors such as lithology (volcanic rocks), high runoff, and the presence of organic acids, which can enhance the chemical weathering. The variability of the trace elements showed a different behavior than major elements. Fe and Al concentrations were correlated with DOC. Dissolved Mn content was correlated with pH, whereas the low concentrations of Cu and Cr are possibly associated with the low content of small size organic colloids. The high values of Zn observed during the decreasing stage suggest biogenic input of Zn to river waters.

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light e...

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light e...

Fertilizer management, in the long term, can affect the amount of P that can be in excess compared to the cultural needs and modify the soil P buffer capacity. These factors can led to P losses from soil to waters, especially via runoff and as particulate P (90% of TP). Soil texture and the amount of organic matter are the main key factors to estimate soil disperdibility but, in turn, the P amount and its forms can also have a dispersive effect and can influence P enrichment of particles potentially lost during runoff processes and its contribution to water eutrophication. The environmental impact due to the P transfer depends on P speciation, because only the inorganic and soluble P forms, or the most degradable organic P ones, are bioavailable. To evaluate the effect of agronomic practices on P losses and on its bioavailability in the long term, soil samples from a middle term experiment have been selected. The field experiment is based on maize cropping systems applying different...

The objective of this research study was to assess the potential of remotely sensed data for estimation of water quality parameters in water bodies. The assessment was based on the field measurements, laboratory examination and data analysis of the collected hyperspectral reflectance data. The factors influencing the qualitative and quantitative nature of the spectra were also analyzed. The hyperspectral data is integrated into ALOS/AVNIR-2 band widths. Examination and correlation of simulated ALOS data reveals that multiplicative two band approach by using Band 4 (NIR) and Band 3 (Red) is best predictor of suspended sediments in water bodies. The ratio of ALOS/AVNIR-2 Band 3 and Band 1 was most closely correlated with Chl-a concentration. For estimation of total suspended sediments (TSS), a higher accuracy was achieved using the Band 4 /Band 2 ratios. Color dissolved organic matters (CDOM) were found to be well correlated with Band 1/Band 2. Regression models were developed and the...

Une base de données numériques d'états de mer en Méditerranée est en cours de construction à partir de simulations effectuées avec le logiciel de TOMAWAC sur la période 1979-2008 afin de venir compléter l'actuelle base de donnée ANEMOC couvrant la façade Atlantique-Manche-Mer du Nord des côtes françaises. Les champs de vent utilisés en entrée sont issus de la réanalyse météorologique NCEP2 du U.S. Climate Diagnostics Center of the National Oceanic and Atmospheric Administration (CDC-NOAA). Les résultats du modèle sont comparés à des mesures de bouées et des mesures satellitaires altimétriques. Les premières comparaisons des résultats de simulations aux mesures montrent un biais moyen négatif (sous-estimation) de la hauteur significative d'état de mer, qu'il convient d'améliorer en travaillant sur les champs de vent et en ajustant les paramètres physiques des termes puits / sources du modèle d'états de mer.

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light e...

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light e...

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light e...

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light e...

Water quality in the Paso Piedras Reservoir has deteriorated, primarily due to periodic blue-green algal blooms, making it temporarily unfit for human consumption. This phenomenon results from the eutrophication of waters of the watershed, and nutrients are considered to be the primary contributors to degradation of freshwater quality. In order to reduce the levels of nitrogen and, most of all, phosphorus, entering the Paso Piedras Reservoir, it is necessary to understand the incidence of diffuse transfers of nutrients from agricultural soils. The nitrogen composition, soluble reactive phosphorus (SRP) and other physico-chemical parameters of the water were analysed in various different parts of the watershed in order to characterize water input to the reservoir from areas with different anthropogenic activity. The upper Sauce Grande basin was divided into three areas with different edaphic characteristics. The physico-chemical parameters measured in sampling surveys included: SRP, ammonium and nitrate, pH, conductivity, turbidity, and total solids. The results showed that the water of the Sauce Grande (areas 1 and 2) was not strongly contaminated, but in El Divisorio (Area 3, which is a sub-watershed whose stream flows directly into the Paso Piedras Reservoir), the levels of conductivity, total suspended sediments and SRP were so high that its contribution to the reservoir accounts for nearly 50% of the total SRP input. The main characteristics of El Divisorio watershed that make it a diffuse source of SRP were not only that its soils, under agriculturallivestock production, have significant slopes, so that water and wind erosion are faster, but also that human intervention had caused the destruction of aggregates. The results showed the influence of the soil characteristics, production systems and the micro-environment developed in the reservoir on the characteristics of waters flowing out of the reservoir. The two villages located in Area 2 had no significant influence on the concentration of nitrogen compounds and SRP found downstream.

This document describes work undertaken as part of a programme of study at the International Institute for Geo-information Science and Earth Observation. All views and opinions expressed therein remain the sole responsibility of the author, and do not necessarily represent those of the institute.

Une base de données numériques d'états de mer en Méditerranée est en cours de construction à partir de simulations effectuées avec le logiciel de TOMAWAC sur la période 1979-2008 afin de venir compléter l'actuelle base de donnée ANEMOC couvrant la façade Atlantique-Manche-Mer du Nord des côtes françaises. Les champs de vent utilisés en entrée sont issus de la réanalyse météorologique NCEP2 du U.S. Climate Diagnostics Center of the National Oceanic and Atmospheric Administration (CDC-NOAA). Les résultats du modèle sont comparés à des mesures de bouées et des mesures satellitaires altimétriques. Les premières comparaisons des résultats de simulations aux mesures montrent un biais moyen négatif (sous-estimation) de la hauteur significative d'état de mer, qu'il convient d'améliorer en travaillant sur les champs de vent et en ajustant les paramètres physiques des termes puits / sources du modèle d'états de mer.

Two field campaigns were used to demonstrate the usefulness of an atmospheric correction method specifically developed for Case 2 waters. The correction method utilizes bio-optical reflectance modeling and principal component analysis. The MODTRAN radiative transfer code simulations were conducted to obtain a statistical database for varying atmospheric situations. Bio-optical reflectance model takes into account the water quality and it&#39;s influence on the detected reflectance. Both field campaigns represent high concentrations of optically active substances such as chlorophyll-a, total suspended sediment and humus. The first field campaign was held at a coastal site of Finland, on the Gulf of Finland, while the other field campaign represents a Finnish lake water area. On both campaigns MERIS satellite instrument and airborne spectrometer data were available.

... The low pH buffering capacity in combination with the reigning redox conditions, as can be seen in Table 2, creates a reducing environment, thus ensuring the presence of substantial amounts of Fe 2+ in the groundwater ([AMINAL, 1995], [Blommaert et al., 1988] and [VLM, 1997 ...

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light e...

Basin, located at the head of Chignecto Bay, Bay of Fundy, exhibits a seaward (exponential) decreasing, time-dependent, surface sediment concentration. There is a strong correlation between suspended sediment concentration and longitudinal concentration gradient. A similar correlation was found in Shepody Bay, Chignecto Bay, and Minas Basin, suggesting that an equilibrium condition exists between the two variables. Total suspended mass in Cumberland Basin was constant over 2 years of observation (10 TM g) despite changes in sediment concentration and concentration gradient. Temporal controls on suspended sediment concentration are fiver influx, ice melting, dispersion, settling on the intertidal mud flats, and water mass exchange at the mouth of the basin. This exchange is due to cross-channel velocity variations; exchanges due to tidal current asymmetry and settling lag are small. A simple box model was developed to study the temporal variation of total suspended sediment in the basin. The results show that the water mass exchange at the basin mouth varies with time and is the dominant factor controlling suspended mass due to efficient dampening of temporal fluctuations in suspended mass. 1. where So is the value of S at x-15, t is time [Greenberg and Amos, 1983], and K• is an empirical coefficient. It follows that the sediment concentration gradient (OS/Ox) in the estuarine water mass at any time is directly related to K• and S OS/Ox =-Kl(t)S(x, t) loge 10 15 > x > 45 km (lb) The parameter K• is therefore an important index of estuarine sedimentary character, but on what does K• depend? Observations in Shepody Bay and Chignecto Bay, Bay of Fundy, show similar trends in suspended sediment concentration. These estuaries differ markedly, however, in scale, geometry, degree of wave exposure, ice influences, and sediment type. Can an exponent K1 be defined for these estuaries, and if so, what is the significance of this to estuaries in general? Cumberland Basin has been well studied. Consequently, it is used first to evaluate the longitudinal distribution of surface suspended sediment concentration within the tidal prism with time, to verify the down-estuary exponential decrease in suspended sediment concentration below the turbidity maximum and to derive values of K• through time.

An original method coupling a spherical factor analysis and a series of kriging is applied in the English Channel to the spatial interpolation of a sampled grain size distribution dataset. The number of factorial axes produces various spatial repartitions of bottom sediments numerically degraded with respect to the original data. These surficial sediments characterizations varying by their correlation degrees towards the sampled data are integrated to a hydrodynamic and sediment transport model. The modeling procedure is based on the coupling of the three-dimensional tidal circulation model COHERENS with multicomponent sediment transport modules. The analysis identifies the variability of “key” parameters of (i) hydrodynamic like the bottom roughness, the current amplitude and the bottom shear stress and (ii) sediment transport such as bedload and suspended load transport rates. A low sensitivity of current predictions is obtained. This result contrasts with the noticeable variabili...

Former mining activities lasting 140 years in the Ducktown Mining District, Tennessee, USA, has contaminated the streams draining the district with acid-mine drainage (AMD). North Potato Creek and its major tributary, Burra Burra Creek, are two of the most heavily AMD-impacted streams in the district. The removal of dissolved metals from the water in these creeks is largely attributable to the sorption of Cu, Zn, Co, Al, and Mn on suspended hydroxide precipitates of Fe. The fraction of trace metals remaining in solution decreases with increasing pH in the sequence Pb<Cu<Zn<Co. The concentration of Fe in solution also decreases with increasing pH due to the formation of ferric hydroxide precipitates which accounted for up to 81.4% by weight of the total suspended sediment. The concentration of suspended sediment substantially decreases as the water of North Potato Creek flows through a large settling basin, where 1.3 (±0.3)×10 6 kg/ year of trace-metal-laden suspended sediment would be annually deposited. In spite of this attempt to purify it, the water discharged into the river is acidic (pH 3.6) and still contains high concentrations of dissolved trace metals, which would resorb on to suspended sediment and be ultimately transported to a downstream reservoir, Ocoee No. 3 Lake.

The CANWET (Canadian ArcView Nutrient and Water Evaluation Tool) and HSPF (Hydrologic Simulation Program-FORTRAN) models were applied to Upper Canagagigue Creek watershed of the Grand River basin in southern Ontario, Canada, for hydrology and sediment evaluations. Both the models have similarity in structure where CANWET is simpler, both in algorithms and use, than HSPF. The outputs of both the models for water budgeting components were compared on annual, seasonal, and monthly basis. The water budget components, evapotranspiration, surface runoff, and subsurface runoff produced by both the models were comparable on annual and seasonal time steps; however, there were some discrepancies in monthly and daily simulations. The seasonal, monthly, and daily Nash-Sutcliffe efficiency coefficient with observed stream flows were 0.83, 0.81, and 0.48 for HSPF, respectively, and 0.80, 0.67, and 0.24 for CANWET, respectively. The monthly and daily simulations by HSPF model were better since HSPF algorithm has more control on temporal variation in parameters sensitive for hydrologic simulations. The sediment simulations by both the models were consistently close for erosion and sediment yield on annual basis. However, superiority in predictions for total suspended sediment yield of one model over the other could not be concluded because of lack of observed data. The daily load of sediment modeled by HSPF followed flow peaks and available observed sediment data points.

Dans ce travail on s'intéresse à une modélisation numérique qui permet de décrire la prise en compte de la houle dans un écoulement généré par les courants de marée. Notre contribution à cette étude a été réalisée à partir de deux modèles : le modèle MECCA, et le modèle SWAN. L'interaction houle-courant a été incluse. Les résultats entrepris dans ce travail montrent l'effet de la superposition de la houle et du courant sur le cisaillement au fond par rapport au courant seul. Autrement dit, près du fond, l'effet de la houle augmente la turbulence, de ce fait, le cisaillement et le frottement augmentent en entraînant une réduction de la vitesse près du fond.

La maintenance des chenaux de navigation et des zones portuaires implique la réalisation d'opérations de dragage pour garantir une profondeur d'eau suffisante. Les produits de dragages sont déposés en mer (opération de clapage) si les conditions d'immersion fixées par la convention d'Oslo sont satisfaites. Toutefois, le clapage de sédiments peut induire des nuisances sur l'environnement. Nous utilisons un modèle de transport sédimentaire à deux phases que nous avons développé (BARBRY et al., 2000 ; NGUYEN et al., 2009 ; CHAUCHAT et al., 2008) pour simuler le phénomène de clapage de sédiment fin. La comparaison des simulations aux résultats expérimentaux réalisés en canal par BOUTIN (2000), VILLARET et al. (1997) et VILLARET et al. (1998) montre le bon comportement du modèle pour décrire les différentes phases dynamiques de ce phénomène.

Discharge and suspended sediment were measured throughout the ablation seasons between May and October 1999 and 2000 in the proglacial stream that drains the Gangotri Glacier into the Ganges River basin. During the observation periods in 1999 and 2000, the total discharge volume was estimated to be 581.87 and 547.47 x 10 6 m', respectively, and the total suspended sediment was 165.62 and 104.99 x 10 4 t, respectively. The lower discharge and suspended sediment in the 2000 season are in response to lower snow and glacier icemelt. A large part of the total discharge volume and suspended sediment was contributed between July and September when solar radiation is strong. Marked variations were noticed in the mean daily discharge and suspended sediment concentrations in different months under the influence of seasonal flushing events during both the study years. However, the mean daily discharge and suspended sediment concentration are more loosely correlated on the seasonal scale in 2000. The rate of decline of suspended sediment is much greater than that of the discharge in both years. Key words meltwater discharge; suspended sediments; discharge volume; Gangotri Glacier; Garhwal Himalaya; India Débits et matières en suspension dans les eaux de fonte du glacier de Gangotri, Himalaya du Garhwal, Inde ' échelle de la saison pour 1 ' année 2000. Le taux de décroissance de la teneur en matières en suspension est bien plus élevé que celui des volumes écoulés pour les deux années. Mots clefs débits de fonte; matières en suspension; volumes écoulés; glacier de Gangotri, Inde

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light e...

18th World IMACS / MODSIM Congress, Cairns, Australia 13-17 July 2009 http://mssanz.org.au /modsim09 ... Hydrological modelling of coastal catchments in New ... Mark Littleboy1, Jon Sayers2 and Jocelyn Dela-Cruz3 ... 1 NSW Department of Environment and Climate Change, ...

This study describes the geochemistry of dissolved elements in the Caura River and gives information about weathering rates and associated CO 2 consumption in an Orinoco River subbasin. Physicochemical variables (pH, conductivity, HCO 3 − , dissolved O 2 , and temperature), dissolved elements (Na, K, Ca, Mg, Si, Al, Fe, Cu, Mn, Zn, and Cr), total suspended sediments (TSS), and dissolved organic carbon (DOC) concentrations were measured monthly from June 2007 to August 2008 in the Caura River. Major element concentrations (Na, Ca, Mg, and Si) showed an inverse correlation with discharge, whereas K showed high concentration values during the rising waters, probably due to biogenic sources. All these elements are provided mainly from weathering of plagioclases and K feldspars. The weathering rate (riverine flux of dissolved major cations and SiO 2 derived from weathering per unit area) and the CO 2 consumption rate in the Caura basin (15.4 tons km −2 yr −1 and 1.1 × 10 5 mol km −2 yr −1 , respectively) were higher than those reported for the Orinoco basin and other black water river basins. This fact can be due to several factors such as lithology (volcanic rocks), high runoff, and the presence of organic acids, which can enhance the chemical weathering. The variability of the trace elements showed a different behavior than major elements. Fe and Al concentrations were correlated with DOC. Dissolved Mn content was correlated with pH, whereas the low concentrations of Cu and Cr are possibly associated with the low content of small size organic colloids. The high values of Zn observed during the decreasing stage suggest biogenic input of Zn to river waters.