Search

Your search keyword '"WEO Department"' showing total 3 results
Start Over Author "WEO Department" Topic 13. climate action
3 results on '"WEO Department"'

1. A graphical method to study suspended sediment dynamics during flood events in the Wadi Sebdou, NW Algeria (1973-2004)

Author

Sylvain Ouillon, Abdelali Terfous, A. Megnounif, Laboratoire EOLE, Université Aboubekr Belkaid - University of Belkaïd Abou Bekr [Tlemcen], Laboratoire de Génie de la Conception (LGeco), Institut National des Sciences Appliquées - Strasbourg (INSA Strasbourg), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), Echanges Côte-Large (ECOLA), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA), Institut de Mécanique des Fluides et des Solides (IMFS), École Nationale du Génie de l'Eau et de l'Environnement de Strasbourg (ENGEES)-Centre National de la Recherche Scientifique (CNRS), WEO Department, and University of sciences and technologies of hanoi (USTH)

Subjects
010504 meteorology & atmospheric sciences, Wadi, 0207 environmental engineering, Suspended sediment concentration, 02 engineering and technology, Rating curve, Structural basin, 01 natural sciences, Flood, medicine, Clockwise, 020701 environmental engineering, ComputingMilieux_MISCELLANEOUS, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, Water Science and Technology, Hydrology, geography, geography.geographical_feature_category, Flood myth, Hysteresis, Sediment, Seasonality, medicine.disease, 6. Clean water, 13. Climate action, Algeria, [SDE]Environmental Sciences, Sedimentary rock, Semiarid watershed, Geology
Abstract

International audience; Small sub-basins are numerous in Mediterranean area and global sedimentary budgets cannot be obtained without a detailed understanding of the hydroclimatic processes that govern sediment fluxes in these small river systems. In this study, the shape of the relationship between sediment concentration (C) and water discharge (Q) during flood events of a 31-years period (1973-2004) was analyzed at the outlet of the Wadi Sebdou basin (256 km2) in northwest Algeria, using a new graphical analysis method based on features of hysteresis loops. Each flood was decomposed as successive stages - each of which being characterized by a sediment rating curve - and used to quantify the contribution of diverse sediment sources within the basin. Seven common classes of hydrological events (single valued and six hysteresis loops: clockwise, counter-clockwise, eight-shaped, single valued plus one loop, either clockwise or counter-clockwise, and single valued plus at least two loops) were explored. Sediment supply from locally derived sources (or "base load") was high and reached 77% of total sediment yield for the study period, and was attributed to weathering of bed material or gullies. The remainder portion was derived from hill-slopes, re-suspension of fresh fine deposits in the river bed, or bank collapse. The ratio of suspended sediment load derived from active sediment source varies considerably from one flood to another depending on many factors, such as seasonality and antecedent type of flood. The simpler floods were the most frequent ones but produced less sediment. The most frequent floods were clockwise or anticlockwise (52% of floods) but brought only 34% of the total sediment flux. The 18% of the most complex floods (single valued plus at least two loops) produced more than 53% of the sediments, mainly supplied by base load (84%). Intra-annual variability was very high. Over 31-years, the five biggest floods cumulated 64% of the total sediment flux and were of three classes, the most complex floods being dominant. The largest contribution occurred during one single 33-days long hydrological event with complex form which represented 26% of the total sediment flux. Apart from the five biggest flood events, the base load represented 53%. The biggest floods favour base load as compared to the smallest ones.

Published
2013
Full Text
View/download PDF

2. Seasonal effect on trace metal elements behaviour in a reservoir of northern Thailand

Author

Warinya Thothong, Marie-Paule Bonnet, Arthorn Boonsaner, Séraphine Grellier, Christelle Lagane, Jl Janeau, Patrick Seyler, WEO Department, University of sciences and technologies of hanoi (USTH), Biogéochimie et écologie des milieux continentaux (Bioemco), Centre National de la Recherche Scientifique (CNRS)-AgroParisTech-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Recherche Agronomique (INRA)-École normale supérieure - Paris (ENS Paris), National Park, Wild Life and Plant Conservation Department (DNP), National Park Wild Life and Plant Conservation Department, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), University of Science and Technology of Hanoi (USTH), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-AgroParisTech-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-AgroParisTech-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)

Subjects
Pollution, Wet season, VARIATION SAISONNIERE, 010504 meteorology & atmospheric sciences, media_common.quotation_subject, Fresh Water, 010501 environmental sciences, Management, Monitoring, Policy and Law, 01 natural sciences, MATIERE EN SOLUTION, ELEMENT EN TRACE, Water column, Water Supply, STRATIFICATION, Dry season, Water Pollution, Chemical, Trace metal, Dissolution, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, General Environmental Science, media_common, Hydrology, General Medicine, Thailand, Anoxic waters, 6. Clean water, PROFIL VERTICAL, 13. Climate action, Metals, PLUIE, Environmental chemistry, [SDE]Environmental Sciences, METAL LOURD, Environmental science, RESERVOIR, Hypolimnion, POLLUTION DES EAUX CONTINENTALES, MILIEU RURAL, Water Pollutants, Chemical, Environmental Monitoring
Abstract

Trace metal elements (TME) can be real threats for living organisms. However, few studies dealt with TME in reservoirs in rural areas where farming practises could induce negative effects. Mae Thang res- ervoir (northern Thailand) has been studied for 3 years to understand the seasonal behaviour of dissolved TME: Fe, Mn, Cd, Al, Pb, V, Cr, Co, Ni, Cu, Zn, Mo, U and As and associated physicochemical parameters. In situ measure- ments of these parameters were done during the dry and the wet seasons as well as water samples along the water column for further analyses and TME determination by inductively coupled plasma-mass spectrometry (ICP- MS). In the dry season, the water column was character- ized by a strong stratification and anoxic conditions in the hypolimnion. High rain and water input from the water- shed during the wet season induced mixing of the water. All TME, except Ni, Co and Cr were less concentrated in the wet season indicating a dilution effect by water input. There was thus no important dissolved pollution coming from the watershed. The anoxic conditions in the dry season enhanced the reduction of Fe and Mn and the desorption processes. Depth, and thus oxic-anoxic con- ditions were the main drivers of TME in the dry season, while in the wet season, dissolution processes from par- ent rocks of watershed were favoured. The average con- centrations of TME in the reservoir were in the limit of the international and Thai standards. Only localized val- ues in the bottom of the reservoir for Fe and Mn were higher than the limits.

Published
2013

3. Positive versus negative environmental impacts of tree encroachment in South Africa

Author

Séraphine Grellier, Simon Lorentz, Luc Abbadie, Pascal Podwojewski, David Ward, Sébastien Barot, Jean-Louis Janeau, Christian Valentin, WEO Department, University of sciences and technologies of hanoi (USTH), University of KwaZulu-Natal (UKZN), Biogéochimie et écologie des milieux continentaux (Bioemco), Centre National de la Recherche Scientifique (CNRS)-AgroParisTech-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Recherche Agronomique (INRA)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), University of Science and Technology of Hanoi (USTH), University of KwaZulu-Natal [Durban, Afrique du Sud] (UKZN), École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-AgroParisTech-Centre National de la Recherche Scientifique (CNRS)

Subjects
0106 biological sciences, INVASION, Acacia, DIVERSITE SPECIFIQUE, SAVANE, QUALITE, 010603 evolutionary biology, 01 natural sciences, Grassland, AZOTE, COMPETITION INTERSPECIFIQUE, PROPRIETE PHYSICOCHIMIQUE, DYNAMIQUE DE VEGETATION, Magnesium ion, Ecology, Evolution, Behavior and Systematics, Nature and Landscape Conservation, 2. Zero hunger, Biomass (ecology), geography, geography.geographical_feature_category, BIOMASSE, biology, SOL, Ecology, Agroforestry, STRATE HERBACEE, PATURAGE, Acacia sieberiana, ARBUSTE, PLANTE FOURRAGERE, 04 agricultural and veterinary sciences, Soil carbon, 15. Life on land, Herbaceous plant, biology.organism_classification, CARBONE, Agronomy, 13. Climate action, [SDE]Environmental Sciences, 040103 agronomy & agriculture, 0401 agriculture, forestry, and fisheries, HERBACEE, ZONE DE MONTAGNE, Woody plant, IMPACT SUR L'ENVIRONNEMENT
Abstract

International audience; Woody plant encroachment in grasslands is a worldwide phenomenon. Despite many studies, the consequences of woody plant encroachment on sub-canopy vegetation and soil properties are still unclear. To better understand the impacts of trees on grassland properties we examined the following questions using a mountainous sub-tropical grassland of South Africa encroached by an indigenous tree, Acacia sieberiana as a case study: (1) Do trees increase sub-canopy herbaceous diversity, quality and biomass and soil nitrogen content? (2) Do large trees have a stronger effect than medium-sized trees on grass and soil properties? (3) Does the impact of trees change with the presence of livestock and position of trees in a catena? We studied grass and non-graminoid species diversity and biomass, grass quality and soil properties during the wet season of 2009. Nitrogen in grass leaves, soil cation exchange capacity and calcium and magnesium ion concentrations in the soil increased under tall Acacia versus open areas. Medium-sized Acacia decreased the gross energy content, digestibility and neutral detergent fibre of grasses but increased the species richness of non-graminoids. Tall and medium Acacia trees were associated with the presence of Senecio inaequidens, an indigenous species that is toxic to horses and cattle. The presence of livestock resulted in a decrease in herbaceous root biomass and an increase in soil carbon and leaf biomass of grass under Acacia. Tree position in the catena did not modify the impact of trees on the herbaceous layer and soil properties. For management of livestock we recommend retaining tall Acacia trees and partially removing medium-sized Acacia trees because the latter had negative effects on grass quality.

Published
2013
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results