scholarly journals Determination of the Hydrodynamic Parameters of Two Types of Soil in the Senegal River Delta. Simulation of Hydro-saline Transfers: Application to the Wind Deflation Phenomenon

2021 ◽  
pp. 24-34
Author(s):  
Fary Diome ◽  
Landing Biaye
Keyword(s):  
Water Table ◽  
Salt Water ◽  
River Delta ◽  
Hydrodynamic Characteristics ◽  
Evaporative Demand ◽  
Senegal River ◽  
Hydrodynamic Parameters ◽  
Massive Structure ◽  
Undisturbed Samples ◽  
Van Genuchten Model

In the Senegal River delta, the presence of a shallow salt water table associated with a strong evaporative demand sometimes leads to an upwelling of salts that crystallize on the surface. This phenomenon can be observed in the vicinity of the Diawling Basin, where a powdery structure sensitive to wind deflation and a massive structure with a fractionation into platelets that cannot be transported by the wind are noted. To understand the hydrodynamic characteristics of these soils, we used numerical simulation of water and solute transfers. The hydrodynamic parameters were determined in the laboratory using Wind's method on undisturbed samples. The experimental retention h() and hydraulic conductivity K(h) curves were fitted using the Van Genuchten model. The simulations show that the soil with a powdery structure has hydrodynamic characteristics that favour the ascent of salts from the water table to the surface. For the soil with a massive structure, the hydrodynamic conditions impose a deposition of salts in the subsurface.

scholarly journals Impacts of Irrigation Water on the Hydrodynamics and Saline Behavior of the Shallow Alluvial Aquifer in the Senegal River Delta

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 311
Author(s):  
Abdoul Aziz Gning ◽  
Philippe Orban ◽  
Raymond Malou ◽  
Joost Wellens ◽  
Johan Derouane ◽  
...  
Keyword(s):  
Water Table ◽  
Shallow Groundwater ◽  
Monitoring Network ◽  
Rice Paddy ◽  
Soil Salinization ◽  
River Delta ◽  
Solute Flux ◽  
Saint Louis ◽  
Senegal River ◽  
Soil Zone

The Senegal River Delta located in north-western Senegal is a strategic region for the development of irrigated rice cultivation for achieving rice self-sufficiency. The presence of a shallow salty water table is often considered as a brake to the development of irrigation, by causing salinization of the soil, although the mechanisms of operation are not well known. An experimental study was carried out in a rice paddy located in the village of Ndiaye, 35 km north from Saint Louis, to characterize the water and solute flux processes below the irrigated plots. The objective was to better understand the irrigation-driven dynamics of soil salinization processes. An experimental monitoring network was installed for monitoring the transit of water at the plot level, in the unsaturated zone and in the aquifer. The results show that the supply of water by irrigation contributes to significantly recharging the water table, as shown by the rise in piezometric level, with a concomitant dilution of the water salinity in the soil zone and in the shallow groundwater. However, when irrigation is stopped, the groundwater level and salinity return within a month to their initial level and salinity status because of the evaporative recovery, which strongly governs these processes. Thus, water flow and solute transfers operate in the delta following a recharge–discharge and dilution–concentration cycle controlled by the water balance, and we do not expect to observe in the short- to middle-term any significant reduction in soil salinization processes by drainage.

scholarly journals Partitioning CO<sub>2</sub> net ecosystem exchange fluxes on the microsite scale in the Lena River Delta, Siberia

2018 ◽  
Author(s):  
Tim Eckhardt ◽  
Christian Knoblauch ◽  
Lars Kutzbach ◽  
Gillian Simpson ◽  
Evgeny Abakumov ◽  
...  
Keyword(s):  
Water Table ◽  
Net Ecosystem Exchange ◽  
Growing Season ◽  
Arctic Tundra ◽  
High Water ◽  
Water Levels ◽  
River Delta ◽  
Lena River ◽  
Hydrological Conditions ◽  
Lena River Delta

Abstract. Arctic tundra ecosystems are currently facing rates of amplified climate change. This is critical as these ecosystems store significant amounts of carbon in their soils, which can be mineralized to CO2 and CH4 and released to the atmosphere. To understand how the CO2 net ecosystem exchange (NEE) fluxes will react to changing climatic conditions, it is necessary to understand the individual responses of the physiological processes contributing to CO2 NEE. Therefore, this study aimed: (i) to partition NEE fluxes at the soil-plant-atmosphere interface in an arctic tundra ecosystem; and (ii) to identify the main environmental drivers of these fluxes. Hereby, the NEE fluxes were partitioned into gross primary productivity (GPP) and ecosystem respiration (Reco) and further into autotrophic (RA) and heterotrophic respiration (RH). The study examined flux data collected during the growing season in 2015 using closed chamber measurements in a polygonal tundra landscape in the Lena River Delta, northeastern Siberia. The measured fluxes on the microscale (1 m–10 m) were used to model the NEE, GPP, Reco, RH, RA and net ecosystem production (NPP) over the growing season. Here, for the first time, the differing response of in situ measured RA and RH fluxes from permafrost-affected soils to hydrological conditions have been examined. It was shown that low RA fluxes are associated to a high water table, most likely due to the submersion of mosses, while an effect of water table fluctuations on RH fluxes was not observed. Furthermore, this work found the polygonal tundra in the Lena River Delta to be a sink for atmospheric CO2 during the growing season. Spatial heterogeneity was apparent with the net CO2 uptake at a wet, depressed polygon center being more than twice as high as that measured at a drier polygon rim. In addition to higher GPP fluxes, the differences in NEE between the two microsites were caused by lower Reco fluxes at the center compared to the rim. Here, the contrasting hydrological conditions caused the CO2 flux differences between the microsites, where high water levels lad to lower decomposition rates due to anoxic conditions.

Phytoplankton growth control and risk of cyanobacterial blooms in the lower Senegal River delta region

2008 ◽  
Vol 42 (4-5) ◽  
pp. 1023-1034 ◽  
Author(s):  
Catherine Quiblier ◽  
Christophe Leboulanger ◽  
Seyni Sané ◽  
Philippe Dufour
Keyword(s):  
Growth Control ◽  
Phytoplankton Growth ◽  
River Delta ◽  
Cyanobacterial Blooms ◽  
Delta Region ◽  
Senegal River

scholarly journals SPATIAL MODELING OF BIOMASS PRODUCTION AND RICE YIELD (ORYZA SATIVA L.) IN THE SENEGAL RIVER DELTA

2020 ◽  
Vol 05 (06) ◽  
pp. 79-91
Author(s):  
Eric KALY ◽  
Daouda NGOM ◽  
Sékouna DIATTA ◽  
Abdoul Aziz DIOUF ◽  
Raymond MALOU
Keyword(s):  
Oryza Sativa ◽  
Biomass Production ◽  
Spatial Modeling ◽  
Rice Yield ◽  
Oryza Sativa L ◽  
River Delta ◽  
Senegal River

scholarly journals Numerical Modelling and Experimental Testing of the Hydrodynamic Characteristics for an Open-Frame Remotely Operated Vehicle

2020 ◽  
Vol 8 (9) ◽  
pp. 688
Author(s):  
Qian Li ◽  
Yu Cao ◽  
Boyang Li ◽  
David M. Ingram ◽  
Aristides Kiprakis
Keyword(s):  
Numerical Model ◽  
Experimental Testing ◽  
Offshore Structures ◽  
Nonlinear Flow ◽  
Navier Stokes ◽  
Effective Control ◽  
Hydrodynamic Characteristics ◽  
Remotely Operated Vehicle ◽  
Hydrodynamic Parameters ◽  
And Performance

The remotely operated vehicles (ROVs) are important to provide the technology support for both the traditional offshore structures and rapidly-growing renewable energy facilities during their full-lifecycles, such as site survey, installation, inspection, maintenance and repair. Regarding the motion and performance of a ROV, the understanding of its hydrodynamic properties is essential when exposing to the disturbances of wave and current. In this study, a numerical model is proposed within the frame of an open-source platform OpenFOAM. The hydrodynamics of the adopted ROV (BlueRov2) in its four principal degrees of freedoms (DOFs) is numerically simulated by a Reynolds-Averaged Navier-Stokes (RANS) solver. Meanwhile, an experimental test is carried out by using a novel technique on measuring the hydrodynamic forces and moments. To validate the numerical prediction methodologies, a set of systematic simulations of the ROV subjected to the disturbances caused by various flow conditions are performed. Comparing to the model test measurement, the numerical model proved to be reliable in offering a good estimation of the hydrodynamic parameters. This also indicates that the presented numerical methodologies and experimental techniques can be applied to other types of open-frame ROVs in quantifying the hydrodynamic parameters, capturing the physics of the fluid-structure interaction (FSI) and feature of the turbulent vorticity which are all essential for the effective control of the ROVs under the nonlinear flow disturbances.

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