The Experts below are selected from a list of 187173 Experts worldwide ranked by ideXlab platform
Jiansheng Cao - One of the best experts on this subject based on the ideXlab platform.
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response of soil water movement and groundwater Recharge to extreme precipitation in a headwater catchment in the north china plain
Journal of Hydrology, 2019Co-Authors: Wenbo Zheng, Shiqin Wang, Matthias Sprenger, Bingxia Liu, Jiansheng CaoAbstract:Abstract Soil water storage and movement are highly heterogeneous across landscapes and their response to spatiotemporal variations in meteorological forcing is complex. While different pools of soil water (including bound and mobile water) are observed, the mechanisms of soil water movement in semi-arid and sub-humid regions are not well understood due to high variation in soil water storage conditions. The Taihang Mountain is a headwater region that Recharges both groundwater and surface water systems of the North China Plain, where groundwater levels have been declining and water storage loss is serious. Increasing land cultivation in the Taihang Mountain areas has increased evapotranspiration and reduced both surface runoff and groundwater Recharge. Although extreme precipitation is critical for groundwater Recharge in the headwater regions, the response mechanism of soil water movement and groundwater Recharge remains unclear. In this study, soil water movement and groundwater Recharge mechanisms in a cultivated farmland (FL) and land under natural vegetation (NV) were determined for a normal and an extreme precipitation year through the combined use of soil water content and stable isotopes of water (18O and 2H). Soil water got enriched in δ18O and δ2H (δ18O changed from −11.2 to −7.0‰ at NV and from −11.1 to −4.4‰ at FL; δ2H changed from −71 to −49‰ at NV and from −73 to −30% at FL) with increasing soil depth during the growing season suggesting that winter precipitation was generally transported via advection dispersion flow mechanism. However, this process was accompanied by the mixing of previously enriched soil water after large rain events (20–50 mm/day) during the rainy season in a normal precipitation year. Water movement changed from translatory flow to preferential flow after extreme precipitation in a wet precipitation year. Cultivation intensified water evaporation in the top soil layer (upper 10–20 cm), and induced preferential flow down to 50 cm soil depth under FL relative to land under NV. Thus, cropping significantly reduced groundwater Recharge. Excessive storm during a wet year produced bypass flow after the first rainstorm, which rapidly Recharged deep soil layers (50–100 cm depth). Bypass flow induced by excessive precipitation and contributed the most to groundwater in FL. The observed rapid response of soil water and groundwater to extreme precipitation events is critical for soil and water management to mitigate problems such as nitrate leaching and groundwater contamination in headwater regions of semi-arid and sub-humid areas.
Julio Goncalves - One of the best experts on this subject based on the ideXlab platform.
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Revisiting Recharge and sustainability of the North-Western Sahara aquifers
Regional Environmental Change, 2020Co-Authors: Julio Goncalves, Jade Petersen, Pierre Deschamps, Bruno Hamelin, Christine Vallet-coulomb, Amine ChekirebAbstract:In recent years, geochemical and geophysical studies have challenged the commonly held view that the use of fossil Sahara aquifers is completely unsustainable because they have not been Recharged since the last wet period of the Holocene. Here, we use gravity data and groundwater flow modeling to provide further evidence of modern Recharge of the North-Western Sahara Aquifer System (NWSAS, Algeria, Tunisia, and Libya). The rainfall-Recharge relationship previously established using data from the Gravity Recovery and Climate Experiment (GRACE) allows to produce a time series of the cumulated Recharge of the NWSAS between 1950 and 2016. This reconstruction yields a mean value of 1.3 km^3 year^−1 while a near-zero Recharge is obtained using GRACE data for the current decade. According to our hydrogeological model, the Recharge of the confined aquifer amounts to 0.3 km^3 year^−1, representing almost 25% of the overall Recharge. Comparison with the time evolution of pumping rates reveals that unsustainable exploitation came fully into effect around 1980, causing a tremendous decline in natural outflows. We show here that the natural outflow of the deep aquifer at Gabès (Tunisia), which partly sustains the coastal aquifer of the Djeffara plain, will vanish in the coming decade, highlighting unsustainable aquifer exploitation. Current population growth and climate change projections are both leading to a degree of groundwater over-exploitation which can only become increasingly unsustainable. Only the enforced regulation of irrigation practices supported both by current oasis pilot experiments and future fully integrated hydro-economic models will be effective in limiting this evolution.
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Quantifying paleoRecharge in the Continental Intercalaire (CI) aquifer by a Monte-Carlo inversion approach of 36Cl/Cl data
Applied Geochemistry, 2014Co-Authors: Jade Petersen, Pierre Deschamps, Julio Goncalves, Bruno Hamelin, Jean-luc Michelot, A. Guendouz, K. ZouariAbstract:Past variations of the Recharge is estimated in the Atlas Mountains, the main Recharge area of the Continental Intercalaire (CI) aquifer, one of the major Saharan aquifers, over the last 775 kyr. In this Mediterranean climatic context, continental archives generally record single humid events, grouped in hypothetical time interval and do not offer continuous chronicles of precipitation. We propose to use spatially distributed image data as a temporal constraint, to infer the past Recharge in the Atlas area. Based on a simplified but robust climatic scenario, assuming a piston model, we apply a Markov Chain Monte Carlo (MCMC) inversion approach to attribute a specific Recharge to the last nine interglacial periods and an undifferentiated Recharge to the glacial periods. The interglacial Recharge values vary from a few mm yr−1 to more than 60 mm yr−1. Glacial Recharge is less than 1 mm yr−1. These values are then analyzed in terms of intensity and allow questioning some initial hypothesis, especially the generally accepted value of the initial image value (around image). Our analysis suggests a higher value, around image. This approach allows us to bring out paleoclimatic information retained in these continental archives. Especially, computed Recharges provide reliable evidence that Marine Isotope Stage (MIS) 5 was more humid than the Holocene period in agreement with marine archives that document wet condition in the North Sahara during that period.
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Quantifying paleoRecharge in the Continental Intercalaire (CI) aquifer by a Monte-Carlo inversion approach of 36Cl/Cl data
Applied Geochemistry, 2014Co-Authors: J.o. Petersen, Pierre Deschamps, Julio Goncalves, Jean-luc Michelot, A. Guendouz, J.l. Hamelin, K. ZouariAbstract:Past variations of the Recharge is estimated in the Atlas Mountains, the main Recharge area of the Continental Intercalaire (CI) aquifer, one of the major Saharan aquifers, over the last 775 kyr. In this Mediterranean climatic context, continental archives generally record single humid events, grouped in hypothetical time interval and do not offer continuous chronicles of precipitation. We propose to use spatially distributed 36Cl/Cl36Cl/Cl data as a temporal constraint, to infer the past Recharge in the Atlas area. Based on a simplified but robust climatic scenario, assuming a piston model, we apply a Markov Chain Monte Carlo (MCMC) inversion approach to attribute a specific Recharge to the last nine interglacial periods and an undifferentiated Recharge to the glacial periods. The interglacial Recharge values vary from a few mm yr−1 to more than 60 mm yr−1. Glacial Recharge is less than 1 mm yr−1. These values are then analyzed in terms of intensity and allow questioning some initial hypothesis, especially the generally accepted value of the initial 36Cl/Cl36Cl/Cl value (around View the MathML source133×10-15atat-1). Our analysis suggests a higher value, around View the MathML source175×10-15atat-1. This approach allows us to bring out paleoclimatic information retained in these continental archives. Especially, computed Recharges provide reliable evidence that Marine Isotope Stage (MIS) 5 was more humid than the Holocene period in agreement with marine archives that document wet condition in the North Sahara during that period.
Amine Chekireb - One of the best experts on this subject based on the ideXlab platform.
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Revisiting Recharge and sustainability of the North-Western Sahara aquifers
Regional Environmental Change, 2020Co-Authors: Julio Goncalves, Jade Petersen, Pierre Deschamps, Bruno Hamelin, Christine Vallet-coulomb, Amine ChekirebAbstract:In recent years, geochemical and geophysical studies have challenged the commonly held view that the use of fossil Sahara aquifers is completely unsustainable because they have not been Recharged since the last wet period of the Holocene. Here, we use gravity data and groundwater flow modeling to provide further evidence of modern Recharge of the North-Western Sahara Aquifer System (NWSAS, Algeria, Tunisia, and Libya). The rainfall-Recharge relationship previously established using data from the Gravity Recovery and Climate Experiment (GRACE) allows to produce a time series of the cumulated Recharge of the NWSAS between 1950 and 2016. This reconstruction yields a mean value of 1.3 km^3 year^−1 while a near-zero Recharge is obtained using GRACE data for the current decade. According to our hydrogeological model, the Recharge of the confined aquifer amounts to 0.3 km^3 year^−1, representing almost 25% of the overall Recharge. Comparison with the time evolution of pumping rates reveals that unsustainable exploitation came fully into effect around 1980, causing a tremendous decline in natural outflows. We show here that the natural outflow of the deep aquifer at Gabès (Tunisia), which partly sustains the coastal aquifer of the Djeffara plain, will vanish in the coming decade, highlighting unsustainable aquifer exploitation. Current population growth and climate change projections are both leading to a degree of groundwater over-exploitation which can only become increasingly unsustainable. Only the enforced regulation of irrigation practices supported both by current oasis pilot experiments and future fully integrated hydro-economic models will be effective in limiting this evolution.
Matthias Sprenger - One of the best experts on this subject based on the ideXlab platform.
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response of soil water movement and groundwater Recharge to extreme precipitation in a headwater catchment in the north china plain
Journal of Hydrology, 2019Co-Authors: Wenbo Zheng, Shiqin Wang, Matthias Sprenger, Bingxia Liu, Jiansheng CaoAbstract:Abstract Soil water storage and movement are highly heterogeneous across landscapes and their response to spatiotemporal variations in meteorological forcing is complex. While different pools of soil water (including bound and mobile water) are observed, the mechanisms of soil water movement in semi-arid and sub-humid regions are not well understood due to high variation in soil water storage conditions. The Taihang Mountain is a headwater region that Recharges both groundwater and surface water systems of the North China Plain, where groundwater levels have been declining and water storage loss is serious. Increasing land cultivation in the Taihang Mountain areas has increased evapotranspiration and reduced both surface runoff and groundwater Recharge. Although extreme precipitation is critical for groundwater Recharge in the headwater regions, the response mechanism of soil water movement and groundwater Recharge remains unclear. In this study, soil water movement and groundwater Recharge mechanisms in a cultivated farmland (FL) and land under natural vegetation (NV) were determined for a normal and an extreme precipitation year through the combined use of soil water content and stable isotopes of water (18O and 2H). Soil water got enriched in δ18O and δ2H (δ18O changed from −11.2 to −7.0‰ at NV and from −11.1 to −4.4‰ at FL; δ2H changed from −71 to −49‰ at NV and from −73 to −30% at FL) with increasing soil depth during the growing season suggesting that winter precipitation was generally transported via advection dispersion flow mechanism. However, this process was accompanied by the mixing of previously enriched soil water after large rain events (20–50 mm/day) during the rainy season in a normal precipitation year. Water movement changed from translatory flow to preferential flow after extreme precipitation in a wet precipitation year. Cultivation intensified water evaporation in the top soil layer (upper 10–20 cm), and induced preferential flow down to 50 cm soil depth under FL relative to land under NV. Thus, cropping significantly reduced groundwater Recharge. Excessive storm during a wet year produced bypass flow after the first rainstorm, which rapidly Recharged deep soil layers (50–100 cm depth). Bypass flow induced by excessive precipitation and contributed the most to groundwater in FL. The observed rapid response of soil water and groundwater to extreme precipitation events is critical for soil and water management to mitigate problems such as nitrate leaching and groundwater contamination in headwater regions of semi-arid and sub-humid areas.
Van Linh Nguyen - One of the best experts on this subject based on the ideXlab platform.
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Couplage des systèmes photovoltaïques et des véhicules électriques au réseau Problèmes et solutions
2014Co-Authors: Van Linh NguyenAbstract:Le raccordement des systèmes photovoltaïques (PV) et/ou des systèmes de Recharge des véhicules électriques (VE) au réseau de distribution peut avoir divers impacts sur le fonctionnement du réseau de distribution. Mais par contre, ils recèlent des potentialités de réglage inutilisées jusqu’à présent. C’est pourquoi, l’objectif de cette thèse est de développer des stratégies de contrôle et de gestion optimale pour les onduleurs PV et les systèmes de Recharge des VE afin de : •Réduire le coût total du système PV ou du système de Recharge •Augmenter les performances des onduleurs PV raccordés au réseau •Augmenter le taux de pénétration des systèmes PV et/ou de Recharge des VE Dans le cadre de ce travail, les services système que les systèmes PV et/ou les systèmes de Recharges des VE peuvent apporter au réseau sont élaborés dans un but prospectif : gestion de congestion (réduction de pics de consommation), respect du plan de tension par régulation, absorption/production de puissance réactive selon le besoin, tenue aux creux de tension, amélioration de la qualité de l’énergie.
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Couplage des systèmes photovoltaïques et des véhicules électriques au réseau : problèmes et solutions
2014Co-Authors: Van Linh NguyenAbstract:Le raccordement des systèmes PV ou des systèmes de Recharge des VE au réseau peut avoir des impacts sur le fonctionnement du réseau:• Variation de tension• Déséquilibre de tension entre phases• Impact du caractère intermittent de la ressource solaire• Impact du caractère aléatoire des systèmes de Recharge des VE• Injection d'harmoniques de découpage au réseau si les onduleurs ne sont pas munis de filtres efficaces• Interactions harmoniques entre onduleurs à travers le réseau• Injection de courant continu au réseau• Courants de fuite• Impact sur les pertes• Impact sur la congestion en cas de Recharge des VE…C'est pourquoi, l'objectif de cette thèse est de développer les stratégies de contrôles/commandes intelligents pour les onduleurs PV et les systèmes de Recharge des VE de afin de- réduire le coût total du système PV ou du système de Recharge,- augmenter la performance des onduleurs PV raccordés au réseau- augmenter le taux de pénétration des systèmes PV ou de Recharge des VE- assurer la continuité de service- participer au réglage de tension et de fréquence du réseau- contribuer à la stabiliser le réseau en cas nécessaire- améliorer la qualité de l'énergie- éviter les congestions…Dans le cadre du travail, la définition des services apportés par systèmes PV ou les systèmes de la Recharge des VE est nécessaire. Ces services que les systèmes PV ou les systèmes de Recharges qui peuvent apporter au réseau, sont élaborés dans un but prospectif : respect du plan de tension par régulation, absorption/production de puissance réactive selon le besoin, tenue aux creux de tension, amélioration de la qualité.Les études concernées :- Etude des interactions (impacts) entre les onduleurs PV et le réseau- Etude des interactions (impacts) entre les onduleurs de la Recharge des VE et le réseau- Définition des services apportés par ces systèmes- Développement et modélisation d'un onduleur bidirectionnel- Développement des systèmes de contrôle/commande intelligent pour ces services:o Réglage de tension. Gestion de congestion. Amélioration de la qualité (ex : harmoniques). Capacité de tenue aux creux de tension.
