Author: "Oloth Sengtaheuanghoung" - Searchworks@Jio Institute Digital Library Search Results

Your search keyword '"Oloth Sengtaheuanghoung"' showing total 35 results

Start Over Author "Oloth Sengtaheuanghoung"

35 results on '"Oloth Sengtaheuanghoung"'

1. From shifting cultivation to teak plantation: effect on overland flow and sediment yield in a montane tropical catchment

Author: Olivier Ribolzi, Olivier Evrard, Sylvain Huon, Anneke de Rouw, Norbert Silvera, Keo Oudone Latsachack, Bounsamai Soulileuth, Irène Lefèvre, Alain Pierret, Guillaume Lacombe, Oloth Sengtaheuanghoung, and Christian Valentin
Subjects: Medicine, Science
Abstract: Abstract Soil erosion supplies large quantities of sediments to rivers of Southeastern Asia. It reduces soil fertility of agro-ecosystems located on hillslopes, and it degrades, downstream, water resource quality and leads to the siltation of reservoirs. An increase in the surface area covered with commercial perennial monocultures such as teak plantations is currently observed at the expanse of traditional slash-and-burn cultivation systems in steep montane environments of these regions. The impacts of land-use change on the hydrological response and sediment yields have been investigated in a representative catchment of Laos monitored for 13 years. After the gradual conversion of rice-based shifting cultivation to teak plantation-based systems, overland flow contribution to stream flow increased from 16 to 31% and sediment yield raised from 98 to 609 Mg km−2. This result is explained by the higher kinetic energy of raindrops falling from the canopy, the virtual absence of understorey vegetation cover to dissipate drop energy and the formation of an impermeable surface crust accelerating the formation and concentration of overland flow. The 25-to-50% lower 137Cs activities measured in soils collected under mature teak plantations compared to soils under other land uses illustrate the severity of soil erosion processes occurring in teak plantations.
Published: 2017
Full Text: View/download PDF

2. Suspended sediment source and propagation during monsoon events across nested sub-catchments with contrasted land uses in Laos

Author: Sylvain Huon, Olivier Evrard, Elian Gourdin, Irène Lefèvre, Thierry Bariac, Jean-Louis Reyss, Thierry Henry des Tureaux, Oloth Sengtaheuanghoung, Sophie Ayrault, and Olivier Ribolzi
Subjects: Suspended sediments, 137Cs, 210Pbxs, 7Be, Total organic matter composition, Physical geography, GB3-5030, Geology, QE1-996.5
Abstract: Study region: Houay Xon catchment in northern Laos. Study focus: Because agricultural headwater catchments of SE Asia are prone to erosion and deliver a significant proportion of the total suspended sediment supply to major rivers and floodplains, the potential sources of sediments and their dynamics were studied for two successive storm flow events in June 2013. Characterization of suspended sediment loads was carried out along a continuum of 7 monitoring stations, combining analyses of fallout radionuclides, particle borne organic matter and stream water properties. New hydrological insights: Radionuclide activities showed that remobilization of soil particles deposited during the previous rainy season or supplied by riverbank erosion is the dominant process, although pulses of surface-soil derived sediments also propagate downstream. This interpretation is supported by suspended organic matter data that also fingerprints the mixing of surface soil vs. subsurface particles. The study moreover highlights the advantages and the drawbacks of combining fallout radionuclides, particle borne organic matter composition and stream water characteristics to discriminate and quantify sediment sources and dynamics in rural areas undergoing urban sprawl.
Published: 2017
Full Text: View/download PDF

3. Hydrological Regime and Water Shortage as Drivers of the Seasonal Incidence of Diarrheal Diseases in a Tropical Montane Environment.

Author: Laurie Boithias, Marc Choisy, Noy Souliyaseng, Marine Jourdren, Fabrice Quet, Yves Buisson, Chanthamousone Thammahacksa, Norbert Silvera, Keooudone Latsachack, Oloth Sengtaheuanghoung, Alain Pierret, Emma Rochelle-Newall, Sylvia Becerra, and Olivier Ribolzi
Subjects: Arctic medicine. Tropical medicine, RC955-962, Public aspects of medicine, RA1-1270
Abstract: BACKGROUND:The global burden of diarrhea is a leading cause of morbidity and mortality worldwide. In montane areas of South-East Asia such as northern Laos, recent changes in land use have induced increased runoff, soil erosion and in-stream suspended sediment loads, and potential pathogen dissemination. To our knowledge, few studies have related diarrhea incidences to catchment scale hydrological factors such as river discharge, and loads of suspended sediment and of Fecal Indicator Bacteria (FIB) such as Escherichia coli, together with sociological factors such as hygiene practices. We hypothesized that climate factors combined with human behavior control diarrhea incidence, either because higher rainfall, leading to higher stream discharges, suspended sediment loads and FIB counts, are associated with higher numbers of reported diarrhea cases during the rainy season, or because water shortage leads to the use of less safe water sources during the dry season. Using E. coli as a FIB, the objectives of this study were thus (1) to characterize the epidemiological dynamics of diarrhea in Northern Laos, and (2) to identify which hydro-meteorological and sociological risk factors were associated with diarrhea epidemics. METHODS:Considering two unconnected river catchments of 22 and 7,448 km2, respectively, we conducted a retrospective time series analysis of meteorological variables (rainfall, air temperature), hydrological variables (discharge, suspended sediments, FIB counts, water temperature), and the number of diarrheal disease cases reported at 6 health centers located in the 5 southern districts of the Luang Prabang Province, Lao PDR. We also examined the socio-demographic factors potentially affecting vulnerability to the effect of the climate factors, such as drinking water sources, hygiene habits, and recreational water exposure. RESULTS:Using thus a mixed methods approach, we found E. coli to be present all year long (100-1,000 Most Probable Number or MPN 100 mL-1) indicating that fecal contamination is ubiquitous and constant. We found that populations switch their water supply from wells to surface water during drought periods, the latter of which appear to be at higher risk of bacterial contamination than municipal water fountains. We thus found that water shortage in the Luang Prabang area triggers diarrhea peaks during the dry and hot season and that rainfall and aquifer refill ends the epidemic during the wet season. The temporal trends of reported daily diarrhea cases were generally bimodal with hospital admissions peaking in February-March and later in May-July. Annual incidence rates were higher in more densely populated areas and mostly concerned the 0-4 age group and male patients. CONCLUSIONS:We found that anthropogenic drivers, such as hygiene practices, were at least as important as environmental drivers in determining the seasonal pattern of a diarrhea epidemic. For diarrheal disease risk monitoring, discharge or groundwater level can be considered as relevant proxies. These variables should be monitored in the framework of an early warning system provided that a tradeoff is found between the size of the monitored catchment and the frequency of the measurement.
Published: 2016
Full Text: View/download PDF

4. Escherichia coli concentration, multiscale monitoring over the decade 2011–2021 in the Mekong River basin, Lao PDR

Author: Laurie Boithias, Olivier Ribolzi, Emma Rochelle-Newall, Chanthanousone Thammahacksa, Paty Nakhle, Bounsamay Soulileuth, Anne Pando-Bahuon, Keooudone Latsachack, Norbert Silvera, Phabvilay Sounyafong, Khampaseuth Xayyathip, Rosalie Zimmermann, Sayaphet Rattanavong, Priscia Oliva, Thomas Pommier, Olivier Evrard, Sylvain Huon, Jean Causse, Thierry Henry-des-Tureaux, Oloth Sengtaheuanghoung, Nivong Sipaseuth, and Alain Pierret
Subjects: General Earth and Planetary Sciences
Abstract: Bacterial pathogens in surface waters may threaten human health, especially in developing countries, where untreated surface water is often used for domestic needs. The objective of the long-term multiscale monitoring of Escherichia coli ([E. coli]) concentration in stream water, and that of associated variables (temperature (T), electrical conductance (EC), dissolved oxygen concentration ([DO]) and saturation (DO%), pH (pH), oxidation-reduction potential (ORP), turbidity (Turb), and total suspended sediment concentration ([TSS])), was to identify the drivers of bacterial dissemination across tropical catchments. This data description paper presents three datasets (see “Data availability” section) collected at 31 sampling stations located within the Mekong River and its tributaries in Lao PDR (0.6–25 946 km2) from 2011 to 2021. The 1602 records have been used to describe the hydrological processes driving in-stream E. coli concentration during flood events, to understand the land-use impact on bacterial dissemination on small and large catchment scales, to relate stream water quality and diarrhea outbreaks, and to build numerical models. The database may be further used, e.g., to interpret new variables measured in the monitored catchments, or to map the health risk posed by fecal pathogens.
Published: 2022
Full Text: View/download PDF

5. Escherichia coli concentration, multiscale monitoring over the decade 2011–2021 in the Mekong basin, Lao PDR

Author: Laurie Boithias, Olivier Ribolzi, Emma Rochelle-Newall, Chanthanousone Thammahacksa, Paty Nakhle, Bounsamay Soulileuth, Anne Pando-Bahuon, Keooudone Latsachack, Norbert Silvera, Phabvilay Sounyafong, Khampaseuth Xayyathip, Rosalie Zimmermann, Sayaphet Rattanavong, Priscia Oliva, Thomas Pommier, Olivier Evrard, Sylvain Huon, Jean Causse, Thierry Henry-Des-Tureaux, Oloth Sengtaheuanghoung, Nivong Sipaseuth, and Alain Pierret
Abstract: Bacterial pathogens in surface waters may threaten human health, especially in developing countries, where untreated surface water is often used for domestic needs. The objective of the long-term multiscale monitoring of Escherichia coli concentration in stream water, and that of associated variables (temperature, electrical conductance, dissolved oxygen concentration and saturation, pH, oxidation-reduction potential, turbidity, and total suspended sediment concentration), was to identify the drivers of bacterial dissemination across tropical catchments. This data description paper presents three datasets (see section Data availability) collected at 31 sampling stations located within the Mekong river and its tributaries in Lao PDR (0.6–25,946 km2) from 2011 to 2021. The 1,602 records have been used to describe the hydrological processes driving in-stream Escherichia coli concentration during flood events, to understand land-use impact on bacterial dissemination on small and large catchment scales, to relate stream water quality and diarrhea outbreaks, and to build numerical models. The database may be further used e.g. to interpret new variables measured in the monitored catchments, or to map the health risk posed by fecal pathogens.
Published: 2022

6. Experimental and modelling evidence of splash effects on manure borne Escherichia coli washoff

Author: Jean-Louis Janeau, Christian Valentin, Olivier Ribolzi, Thierry Henry-des-Tureaux, Keooudone Latsachack, Emma Rochelle-Newall, Chanthamousone Thammahacksa, Emilie Jardé, Claude Mügler, Marion Viguier, Oloth Sengtaheuanghoung, Modélisation Hydrologique (HYDRO), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), 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), Institut d'écologie et des sciences de l'environnement de Paris (iEES Paris ), Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Department of Agricultural Land Management [Vientiane] (DALaM), Ministry of Agriculture and Forestry of Laos, Pastek program of the GIS-Climat, Institut de recherche pour le développement (IRD), Géosciences Environnement Toulouse, ANR-13-AGRO-0007,TecItEasy,Effets conjugués de l'expansion des plantations d'arbres et du changement climatique sur le fonctionnement hydro-sédimentaire des bassins versants tropicaux de montagne: la diversité microbienne aquatique comme un proxy de la conversion d'usage des terres(2013), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDV.SA]Life Sciences [q-bio]/Agricultural sciences, Runoff, Health, Toxicology and Mutagenesis, Faecal indicator bacteria (FIB), 010501 environmental sciences, Physics-based modelling, Raindrop impact, 01 natural sciences, complex mixtures, Lao PDR, Hydraulic conductivity, Environmental Chemistry, 0105 earth and related environmental sciences, 2. Zero hunger, Hydrology, Splash, fungi, Tropical agro-ecosystems, Sediment, General Medicine, Vegetation, 15. Life on land, Pollution, Manure, 6. Clean water, 13. Climate action, Soil water, Erosion, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Surface runoff
Abstract: International audience; In tropical montane South-East Asia, recent changes in land use have induced increased runoff, soil erosion and in-stream suspended sediment loads. Land use change is also contributing to increased microbial pathogen dissemination and contamination of stream waters. Escherichia coli (E. coli) is frequently used as an indicator of faecal contamination. Field rain simulations were conducted to examine how E. coli is exported from the surface of upland, agricultural soils during runoff events. The objectives were to characterize the loss dynamics of this indicator from agricultural soils contaminated with livestock waste, and to identify the effect of splash on washoff. Experiments were performed on nine 1 m2 plots, amended or not with pig or poultry manure. Each plot was divided into two 0.5 m2 sub-plots. One of the two sub-plots was protected with a mosquito net for limiting the raindrop impact effects. Runoff, soil detachment by raindrop impact and its entrainment by runoff, and E. coli loads and discharge were measured for each sub-plot. The results show that raindrop impact strongly enhances runoff generation, soil detachment and entrainment and E. coli export. When the impact of raindrops was reduced with a mosquito net, total runoff was reduced by more than 50%, soil erosion was on average reduced by 90% and E. coli export from the amended soil surface was on average 3 to 8 times lower. A coupled physics-based approach was performed using the Cast3M platform for modelling the time evolutions of runoff, solid particles detachment and transfer and bacteria transport that were measured for one of the nine plots. After estimation of the saturated hydraulic conductivity, soil erodibility and attachment rate of bacteria, model outputs were consistent with measured runoff coefficients, suspended sediment and E. coli loads. This work therefore underlines the need to maintain adequate vegetation at the soil surface to avoid the erosion and export of soil borne potential pathogens towards downstream aquatic systems.
Published: 2021
Full Text: View/download PDF

7. Linking tree-rooting profiles to leaf phenology: a first attempt on Tectona Grandis Linn F

Author: Chanthanousone Thammahacksa, Bounsamay Soulileuth, Christian Hartmann, Kampaseuth Xayyathip, Corentin Clement, Alain Pierret, Keoudone Latsachack, Jean-Luc Maeght, Phabvilay Sounyafong, Oloth Sengtaheuanghoung, Institut d'écologie et des sciences de l'environnement de Paris (iEES Paris ), Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), International Water Management Institute, Institut d'écologie et des sciences de l'environnement de Paris (IEES), Institut National de la Recherche Agronomique (INRA)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), UMR Climat, Sol, Environnement (UMR CSE), Institut National de la Recherche Agronomique (INRA), Department of Plant Science and Agricultural Resources, Khon Kaen University, Representation du Laos (IRD), NAFRI, National Agricultural and Forestry Research Institute, Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), and Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])
Subjects: 0106 biological sciences, Canopy, 010504 meteorology & atmospheric sciences, Physiology, Plant Science, [SDV.BID.SPT]Life Sciences [q-bio]/Biodiversity/Systematics, Phylogenetics and taxonomy, 01 natural sciences, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, Deep roots · Leaf flushing, Afforestation, Mono-crop teak forest, Tectona grandis, Tropical deciduous tree phenology, 0105 earth and related environmental sciences, Topsoil, Ecology, biology, Phenology, Deep roots, Diameter at breast height, Forestry, [SDV.BV.BOT]Life Sciences [q-bio]/Vegetal Biology/Botanics, 15. Life on land, biology.organism_classification, Leaf flushing, Agronomy, Tectona, [SDE]Environmental Sciences, Soil horizon, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, 010606 plant biology & botany, Woody plant
Abstract: Key message In this study, deep roots of teak tree seem to have acted as a "safety net", allowing trees to maintain their canopy cover longer, thus coping with inter- and intra-seasonal drought. Abstract Most deciduous species of dry monsoon forest, such as teak tree (Tectona grandis Linn F.), establish new foliage slightly before, or at the onset of the rainy season, when the upper soil layers are the driest. This phenomenon suggests that trees rely upon deep water storage to cover their need for the new canopy development. Therefore, we hypothesized that deeper rooted trees may display phenological patterns that confer them physiological advantages with regard to access to water. At an upland location in Northern Laos, we characterized 10 mono-specific teak tree plantations corresponding to micro-environments that differed with regard to soil, slope, elevation, and orientation. We compared the leaf phenology of trees, taking into account their age, diameter at breast height (DBH), and rooting pattern down to 3.5 m depth. With at least 5% of its total fine roots below 2 m, teak trees were found to be deep rooted. There was no correlation between the timing of leaf flushing and rooting depth nor with primary production (assessed on the basis of tree girth increase). Leaf flushing was strongly synchronous with rainfall rather pointing out that its primary determinant is the water status of topsoil and near-surface soil horizons that results from seasonal rainfall, even though the mechanism(s) underlying such a process remain to be clarified. However, deeper rooted teak trees tended to maintain a denser canopy cover over longer periods than trees with shallower rooting systems. This suggests that, deep roots may play a role as a "safety net", i.e., providing improved resilience to inter- and intra-seasonal drought events, but do not influence the timing of the leaf flushing.
Published: 2019
Full Text: View/download PDF

8. The Multiscale <scp>TROPIcal CatchmentS</scp> critical zone observatory <scp>M‐TROPICS</scp> dataset <scp>II</scp> : Land use, hydrology and sediment production monitoring in Houay Pano, northern Lao <scp>PDR</scp>

Author: Chanthamousone Thammahacksa, Norbert Silvera, Sylvain Huon, Khambai Phanthavong, Guillaume Lestrelin, Henri Robain, Keooudone Latsachack, Andrew Noble, Vincent Chaplot, Alain Pierret, Xaysatith Souliyavongsa, Yann Le Troquer, Jean-Pierre Thiébaux, Phapvilay Sounyaphong, Laurie Boithias, Khampaseuth Xayyathip, Jean-Louis Janeau, Kongkeo Phachomphon, Jean Riotte, Stéphane Audry, Olga Vigiak, Yves Auda, Anneke de Rouw, Nivong Sipaseuth, Marion Viguier, Sengkeo Tasaketh, Olivier Ribolzi, Pierre Marchand, Alounsavath Chanhphengxay, Thierry Henry des Tureaux, Anne Pando-Bahuon, Saysongkham Sayavong, Bounsamay Soulileuth, Jean-Luc Maeght, Oloth Sengtaheuanghoung, Jean-Pierre Bricquet, Pierre Moreau, Emma Rochelle-Newall, and Christian Valentin
Subjects: 2. Zero hunger, Hydrology, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, 0207 environmental engineering, Drainage basin, Sediment, Tropics, 02 engineering and technology, 15. Life on land, 01 natural sciences, 6. Clean water, Water level, Catchment hydrology, Hydrology (agriculture), 13. Climate action, Environmental science, Water quality, 020701 environmental engineering, Surface runoff, 0105 earth and related environmental sciences, Water Science and Technology
Abstract: Mountain regions of the humid tropics are characterized by steep slopes and heavy rains. These regions are thus prone to both high surface runoff and soil erosion. In Southeast Asia, uplands are also subject to rapid land-use change, predominantly as a result of increased population pressure and market forces. Since 1998, the Houay Pano site, located in northern Lao PDR (19.85°N 102.17°E) within the Mekong basin, aims at assessing the long-term impact of the conversion of traditional slash-and-burn cultivation systems to commercial perennial monocultures such as teak tree plantations, on the catchment hydrological response and sediment yield. The instrumented site monitors hydro-meteorological and soil loss parameters at both microplot (1 m2) and small catchment (0.6 km2) scales. The monitored catchment is part of the network of critical zone observatories named Multiscale TROPIcal CatchmentS (M-TROPICS). The data shared by M-TROPICS in Houay Pano are (1) rainfall, (2) air temperature, air relative humidity, wind speed, and global radiation, (3) catchment land use, (4) stream water level, suspended particulate matter, bed particulate matter and stones, (5) soil surface features, and (6) soil surface runoff and soil detachment. The dataset has already been used to interpret suspended particulate matter and bed particulate matter sources and dynamics, to assess the impact of land-use change on catchment hydrology, soil erosion, and sediment yields, to understand bacteria fate and weed seed transport across the catchment, and to build catchment-scale models focused on hydrology and water quality issues. The dataset may be further used to e.g. assess the role of headwater catchments in large tropical river basin hydrology, support the interpretation of new variables measured in the catchment (e.g. contaminants other than fecal bacteria), and assess the relative impacts of both climate and land-use change on the catchment.
Published: 2021
Full Text: View/download PDF

9. Understorey vegetation drives surface runoff and soil loss in teak plantation-based system of Northern Laos

Author: Olivier Ribolzi, Laurie Boithias, Bounsamai Soulileuth, Oloth Sengtaheuanghoung, Layheang Song, Alain Pierret, Phabvilay Sounyafong, Norbert Silvera, Chantha Oeurng, Anneke de Rouw, and Christian Valentin
Subjects: Hydrology, Soil loss, Environmental science, Understorey vegetation, Surface runoff
Abstract: Humid tropical mountainous area experiences serious soil erosion due to rapid changes in landuse, sometimes implying erosion prone management practices. In this study, we hypothesized that keeping understorey in teak tree plantation would protect soil and avoid soil erosion. We assessed the effects of 4 management practices in teak tree plantation area on water and soil losses using 6 replicated 1-m2 microplots in four plantations situated in Northern Laos during the wet season of 2017. The landuses in the four plantations were teak without understorey (TNU), teak with low density of understorey (TLU), teak with high density of understorey (THU), and teak with broom grass, Thysanolaena latifolia (TBG). During the wet season of 2017, we monitored surface runoff and soil loss for 22 rainfall events. We also measured some of the teak tree and understorey characteristics (i.e. height and percentage of cover) and the percentage areas of soil surface features (i.e. litter, free aggregates, crusting, etc.). Relationships among these variables was estimated through multiple statistics and regression analyses. We found that runoff coefficient and soil loss were the smallest for THU and TBG: runoff coefficient was 23% for both treatments, and soil losses were 465 and 381 g m-2, respectively. Runoff coefficient and soil loss for TLU were 35% and 1115 g m-2, respectively. We observed the highest runoff coefficient and soil loss under TNU (60%, 5455 g m-2) associated to the highest crusting rate (82%). High runoff coefficient and soil loss under TNU was explained by the kinetic energy of rain drops falling from the broad leaves of the tall teak trees down to bare soil, devoid of plant residues, thus leading to severe soil surface crusting and detachment. Overall, promoting understorey such as broom grass in teak tree plantations would (1) limit surface runoff and improve soil infiltrability, thus increase the soil water stock available for both root absorption and groundwater recharge, and (2) mitigate soil loss and favour soil fertility conservation.
Published: 2020
Full Text: View/download PDF

10. Linking crop structure, throughfall, soil surface conditions, runoff and soil detachment: 10 land uses analyzed in Northern Laos

Author: Anneke de Rouw, Norbert Silvera, Christian Valentin, Olivier Ribolzi, Guillaume Lacombe, Alain Pierret, Phabvilay Sounyafong, Bounsamai Soulileuth, and Oloth Sengtaheuanghoung
Subjects: Environmental Engineering, 010504 meteorology & atmospheric sciences, Erosion control, F08 - Systèmes et modes de culture, Micro-plot experiment, Conservation des sols, 01 natural sciences, Soil crust, couverture du sol, Environmental Chemistry, Couverture végétale, Throughfall kinetic energy, Waste Management and Disposal, Multiple linear regression, 0105 earth and related environmental sciences, P36 - Érosion, conservation et récupération des sols, Hydrology, Utilisation des terres, Montane Southeast Asia, 04 agricultural and veterinary sciences, Plant litter, Throughfall, Pollution, Soil loss, Ruissellement, E11 - Économie et politique foncières, Soil water, 040103 agronomy & agriculture, Erosion, 0401 agriculture, forestry, and fisheries, Environmental science, Plant cover, Surface runoff
Abstract: In Montane Southeast Asia, deforestation and unsuitable combinations of crops and agricultural practices degrade soils at an unprecedented rate. Typically, smallholder farmers gain income from "available" land by replacing fallow or secondary forest by perennial crops. We aimed to understand how these practices increase or reduce soil erosion. Ten land uses were monitored in Northern Laos during the 2015 monsoon, using local farmers' fields. Experiments included plots of the conventional system(food crops and fallow), and land uses corresponding to new market opportunities (e.g. commercial tree plantations). Land uses were characterized by measuring plant cover and plant mean height per vegetation layer. Recorded meteorological variables included rainfall intensity, throughfall amount, throughfall kinetic energy (TKE), and raindrop size. Runoff coefficient, soil loss, and the percentage areas of soil surface types (free aggregates and gravel; crusts; macro-faunal, vegetal and pedestal features; plant litter) were derived from observations and measurements in 1-m(2) micro-plots. Relationships between these variables were explored with multiple regression analyses. Our results indicate that TKE induces soil crusting and soil loss. By reducing rainfall infiltration, crusted area enhances runoff, which removes and transports soil particles detached by splash over non-crusted areas. TKE is lower under land uses reducing the velocity of raindrops and/or preventing an increase in their size. Optimal vegetation structures combine minimum height of the lowest layer (to reduce drop velocity at ground level) and maximum coverage (to intercept the largest amount of rainfall), as exemplified by broom grass (Thysanolaena latifolia). In contrast, high canopies with large leaves will increase TKE by enlarging raindrops, as exemplified by teak trees (Tectona grandis), unless a protective understorey exists under the trees. Policies that ban the burning of multi-layered vegetation structure under tree plantations should be enforced. Shade-tolerant shrubs and grasses with potential economic return could be promoted as understorey.
Published: 2018
Full Text: View/download PDF

11. Experimental and modelling evidence of short-term effect of raindrop impact on hydraulic conductivity and overland flow intensity

Author: Chanthamousone Thammahacksa, Claude Mügler, Marion Viguier, Keooudone Latsachack, Emilie Jardé, Emma Rochelle-Newall, Olivier Ribolzi, Thierry Henri-des-Tureaux, Christian Valentin, Oloth Sengtaheuanghoung, Jean-Louis Janeau, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Modélisation Hydrologique (HYDRO), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Géosciences Environnement Toulouse (GET), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Institut d'écologie et des sciences de l'environnement de Paris (iEES Paris), Institut National de la Recherche Agronomique (INRA)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Géosciences Rennes (GR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Agriculture Land-Use Planning Center, Agence Nationale de la Recherche, IRD, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-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), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), and Institut d'écologie et des sciences de l'environnement de Paris (IEES (UMR_7618 / UMR_D_242 / UMR_A_1392 / UM_113) )
Subjects: 010504 meteorology & atmospheric sciences, Hydraulic conductivity, 0207 environmental engineering, Soil science, 02 engineering and technology, Raindrop impact, 01 natural sciences, GEOF, Soil crusting, Hydrology (agriculture), Lao PDR, Runoff modelling, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, 020701 environmental engineering, Water pollution, 0105 earth and related environmental sciences, Water Science and Technology, Splash, Tropical agro-ecosystems, 15. Life on land, 6. Clean water, Soil conditioner, Soil water, Erosion, Environmental science, Surface runoff
Abstract: International audience; Tropical montane areas of Southeast Asia are exposed to high-intensity rainfall during the monsoon period. This is particularly problematic in areas where soils on steep slopes are cultivated as it can lead to heavy runoff, high soil erosion, and water pollution. The objective of this paper is to analyse the effect of the impact of raindrops on the dynamics of runoff on such steep fields. Experiments under simulated rainfall were performed at the plot scale (1 m2) to quantify water export from the surface of upland agricultural soils during overland flow events. Four 1 m2 plots were divided in duplicated treatment groups: (a) control with no amendments, and (b) amended with pig manure. Each plot was divided into two 0.5 m2 rectangular subplots. One subplot was designated as a rain splash treatment; the other sub-plot was covered with a 2 mm grid size wire screen that was located 12 cm above the soil surface. The purpose of the screen was to break the raindrops into fine droplets and to reduce fall height in order to drastically reduce their kinetic energy. Runoff was measured for each sub-plot. The results show that raindrop impact drastically enhances runoff generation on both bare soils and on manure amended soils. When the impact of raindrops was limited by screening, runoff was higher on amended soils than on bare soils.The temporal evolution of runoff was correctly modelled using a soil hydraulic conductivity that exponentially decreases over time of exposure to rainfall. Both experimental and modelling results showed that droplet energy induces a rapid evolution of the hydraulic properties of the soil surface due to crusting, resulting in a reduction of hydraulic conductivity and a concomitant increase in runoff rate.
Published: 2019
Full Text: View/download PDF

12. Quantifying the effect of overland flow on Escherichia coli pulses during floods: Use of a tracer-based approach in an erosion-prone tropical catchment

Author: Olivier Ribolzi, Cyril Zouiten, Laurie Boithias, Bounsamay Soulileuth, Guillaume Lacombe, Emma Rochelle-Newall, Olivier Evrard, Elodie Robert, Thomas Pommier, Chanthamousone Thammahacksa, Norbert Silvera, Keooudone Latsachack, Yves Auda, Marion Viguier, Sylvain Huon, Oloth Sengtaheuanghoung, 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-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Gestion de l'Eau, Acteurs, Usages (UMR G-EAU), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-AgroParisTech-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro - Montpellier SupAgro, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Département Environnements et Sociétés (Cirad-ES), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), Institut de Recherche pour le Développement (IRD), Institut d'écologie et des sciences de l'environnement de Paris (iEES Paris ), Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Géochimie Des Impacts (GEDI), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Ecologie Microbienne - UMR 5557 (LEM), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Ecole Nationale Vétérinaire de Lyon (ENVL)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Department of Agricultural Land Management [Vientiane] (DALaM), Ministry of Agriculture and Forestry of Laos, ANR-13-AGRO-0007,TecItEasy,Effets conjugués de l'expansion des plantations d'arbres et du changement climatique sur le fonctionnement hydro-sédimentaire des bassins versants tropicaux de montagne: la diversité microbienne aquatique comme un proxy de la conversion d'usage des terres(2013), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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 de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-AgroParisTech-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and 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)
Subjects: Turbidité, 010504 meteorology & atmospheric sciences, Drainage basin, 02 engineering and technology, 01 natural sciences, Panoply, Turbidity, 020701 environmental engineering, Hydrologie, Water Science and Technology, geography.geographical_feature_category, Northern uplands of Lao PDR, Inondation, Contamination biologique, Surface runoff, Ruissellement, 6. Clean water, Circulation de l'eau, S50 - Santé humaine, [SDE]Environmental Sciences, Erosion, Surface-sub surface flow separation, Storm flow, Land-use change, 0207 environmental engineering, faecal pollution [EN], Indicator bacteria, Context (language use), parasitic diseases, Escherichia coli, P10 - Ressources en eau et leur gestion, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, 0105 earth and related environmental sciences, Hydrology, geography, Flood myth, fungi, Fecal coliform, Fecal indicator bacteria, 13. Climate action, Environmental science
Abstract: International audience; Bacterial pathogens in surface waters threaten human health. The health risk is especially high in developing countries where sanitation systems are often lacking or deficient. Considering twelve flash-flood events sampled from 2011 to 2015 at the outlet of a 60-ha tropical montane headwater catchment in Northern Lao PDR, and using Escherichia coli as a fecal indicator bacteria, our objective was to quantify the contributions of both surface runoff and sub-surface flow to the in-stream concentration of E. coli during flood events, by (1) investigating E. coli dynamics during flood events and among flood events and (2) designing and comparing simple statistical and mixing models to predict E. coli concentration in stream flow during flood events. We found that in-stream E. coli concentration is high regardless of the contributions of both surface runoff and sub-surface flow to the flood event. However, we measured the highest concentration of E. coli during the flood events that are predominantly driven by surface runoff. This indicates that surface runoff, and causatively soil surface erosion, are the primary drivers of in-stream E. coli contamination. This was further confirmed by the step-wise regression applied to instantaneous E. coli concentration measured in individual water samples collected during the flood events, and by the three models applied to each flood event (linear model, partial least square model, and mixing model). The three models showed that the percentage of surface runoff in stream flow was the best predictor of the flood event mean E. coli concentration. The mixing model yielded a Nash-Sutcliffe efficiency of 0.65 and showed that on average, 89% of the in-stream concentration of E. coli resulted from surface runoff, while the overall contribution of surface runoff to the stream flow was 41%. We also showed that stream flow turbidity and E. coli concentration were positively correlated, but that turbidity was not a strong predictor of E. coli concentration during flood events. These findings will help building adequate catchment-scale models to predict E. coli fate and transport, and mapping the related risk of fecal contamination in a global changing context.
Published: 2021
Full Text: View/download PDF

13. Understory Limits Surface Runoff and Soil Loss in Teak Tree Plantations of Northern Lao PDR

Author: Christian Valentin, Layheang Song, Anneke de Rouw, Chantha Oeurng, Bounchanh Lattanavongkot, Phabvilay Sounyafong, Alain Pierret, Olivier Ribolzi, Oloth Sengtaheuanghoung, Norbert Silvera, Bounsamay Soulileuth, Laurie Boithias, Bounthan Souksavath, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), 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), Department of Agricultural Land Management [Vientiane] (DALaM), Ministry of Agriculture and Forestry of Laos, Institut d'écologie et des sciences de l'environnement de Paris (iEES Paris ), and Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
Subjects: Wet season, lcsh:Hydraulic engineering, 010504 meteorology & atmospheric sciences, Geography, Planning and Development, teak tree plantation, South East Asia, 010501 environmental sciences, Aquatic Science, 01 natural sciences, Biochemistry, lcsh:Water supply for domestic and industrial purposes, overland flow, lcsh:TC1-978, inter-rill erosion, 0105 earth and related environmental sciences, Water Science and Technology, [SDV.EE]Life Sciences [q-bio]/Ecology, environment, lcsh:TD201-500, broom grass, soil erosion, Land use, Broom, land management, Understory, Groundwater recharge, Agronomy, understory, Soil water, Environmental science, Soil fertility, Surface runoff, South–East Asia
Abstract: Many mountainous regions of the humid tropics experience serious soil erosion following rapid changes in land use. In northern Lao People&rsquo, s Democratic Republic (PDR), the replacement of traditional crops by tree plantations, such as teak trees, has led to a dramatic increase in floods and soil loss and to the degradation of basic soil ecosystem services such as water filtration by soil, fertility maintenance, etc. In this study, we hypothesized that conserving understory under teak trees would protect soil, limit surface runoff, and help reduce soil erosion. Using 1 m2 microplots installed in four teak tree plantations in northern Lao PDR over the rainy season of 2017, this study aimed to: (1) assess the effects on surface runoff and soil loss of four understory management practices, namely teak with no understory (TNU, control treatment), teak with low density of understory (TLU), teak with high density of understory (THU), and teak with broom grass, Thysanolaena latifolia (TBG), (2) suggest soil erosion mitigation management practices, and (3) identify a field visual indicator allowing a rapid appraisal of soil erosion intensity. We monitored surface runoff and soil loss, and measured teak tree and understory characteristics (height and percentage of cover) and soil surface features. We estimated the relationships among these variables through statistics and regression analyses. THU and TBG had the smallest runoff coefficient (23% for both) and soil loss (465 and 381 g&middot, m&minus, 2, respectively). The runoff coefficient and soil loss in TLU were 35% and 1115 g&middot, 2, respectively. TNU had the highest runoff coefficient and soil loss (60%, 5455 g&middot, 2) associated to the highest crusting rate (82%). Hence, the soil loss in TBG was 14-times less than in TNU and teak tree plantation owners could divide soil loss by 14 by keeping understory, such as broom grass, within teak tree plantations. Indeed, a high runoff coefficient and soil loss in TNU was explained by the kinetic energy of rain drops falling from the broad leaves of the tall teak trees down to bare soil, devoid of plant residues, thus leading to severe soil surface crusting and soil detachment. The areal percentage of pedestal features was a reliable indicator of soil erosion intensity. Overall, promoting understory, such as broom grass, in teak tree plantations would: (1) limit surface runoff and improve soil infiltrability, thus increase soil water stock available for both root absorption and groundwater recharge, and (2) mitigate soil loss while favoring soil fertility conservation.
Published: 2020
Full Text: View/download PDF

14. Modeling the Impact of Land Use Change on Basin-scale Transfer of Fecal Indicator Bacteria: SWAT Model Performance

Author: Kyung Hwa Cho, Olivier Ribolzi, Minjeong Kim, Laurie Boithias, and Oloth Sengtaheuanghoung
Subjects: Environmental Engineering, Watershed, Soil and Water Assessment Tool, 0208 environmental biotechnology, 02 engineering and technology, 010501 environmental sciences, Management, Monitoring, Policy and Law, 01 natural sciences, Soil, Rivers, Land use, land-use change and forestry, SWAT model, Waste Management and Disposal, 0105 earth and related environmental sciences, Water Science and Technology, Hydrology, Suspended solids, Land use, Bacteria, Water, Models, Theoretical, Pollution, 020801 environmental engineering, Soil water, Environmental science, Surface runoff
Abstract: Land use change from annual crops to commercial tree plantations can modify flow and transport processes at the watershed scale, including the fate and transport of fecal indicator bacteria (FIB), such as Escherichia coli. The Soil and Water Assessment Tool (SWAT) is a useful means for integrating watershed characteristics and simulating water and contaminants. The objective of this study was to provide a comprehensive assessment of the impact of land use change on microbial transfer from soils to streams using the SWAT model. This study was conducted for the Houay Pano watershed located in northern Lao People's Democratic Republic. Under the observed weather conditions, the SWAT model predicted a decrease from 2011 to 2012 and an increase from 2012 to 2013 in surface runoff, suspended solids, and E. coli transferred from the soil surface to streams. The amount of precipitation was important in simulating surface runoff, and it subsequently affected the fate and transport of suspended solids and bacteria. In simulations of identical weather conditions and different land uses, E. coli fate and transport was more sensitive to the initial number of E. coli than to its drivers (i.e., surface runoff and suspended solids), and leaf area index was a significant factor influencing the determination of the initial number of E. coli on the soil surface. On the basis of these findings, this study identifies several limitations of the SWAT fertilizer and bacteria modules and suggests measures to improve our understanding of the impacts of land use change on FIB in tropical watersheds.
Published: 2018

15. Interacting land use and soil surface dynamics control groundwater outflow in a montane catchment of the lower Mekong basin

Author: Anneke de Rouw, Phabvilay Sounyafong, Bounsamai Soulileuth, Oloth Sengtaheuanghoung, Sylvain Huon, Guillaume Lacombe, Olivier Ribolzi, Norbert Silvera, Emmanuel Mouche, Alain Pierret, Keo Oudone Latxachak, Henri Robain, Christian Valentin, Université Fédérale Toulouse Midi-Pyrénées, International Water Management Institute, International Water Management Institute, Vientiane, Biogéochimie et écologie des milieux continentaux (Bioemco), 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 de Recherche pour le Développement (IRD), Representation du Laos (IRD), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Modélisation Hydrologique (HYDRO), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), National Agriculture and Forestry Research Institute (NAFRI), Université de Toulouse (UT), 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 Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: Érosion hydrique, F08 - Systèmes et modes de culture, 0208 environmental biotechnology, 02 engineering and technology, Hydrologic connectivity, Bassin versant, Streamflow, Evapotranspiration, Electrical resistivity tomography (ERT), Hydrological modelling, P10 - Ressources en eau et leur gestion, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS, P36 - Érosion, conservation et récupération des sols, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, 2. Zero hunger, Hydrology, Baseflow, Ecology, Discharge, Culture itinérante, Montagne, Groundwater recharge, 15. Life on land, 6. Clean water, eau souterraine, 020801 environmental engineering, Infiltration (hydrology), Storm and inter-storm streamflow, 13. Climate action, Environmental science, Animal Science and Zoology, Tracer-based hydrograph separation, Surface runoff, Agronomy and Crop Science, Groundwater
Abstract: Groundwater contribution to streamflow sustains biodiversity and enhances ecosystem services, especially under monsoon-driven climate where stream baseflow is often the only available water resource during the dry season. We assessed how land use change influences streamflow and its groundwater contribution in a small headwater catchment subject to shifting cultivation in Montane Southeast Asia. Continuous time series of rainfall, reference evapotranspiration, groundwater level, stream discharge and electrical conductivity (EC) of surface and groundwater were monitored from 2002 to 2007. With the rainfall-runoff model GR4J, we investigated temporal changes in the hydrological behaviour of the study catchment to verify consistencies with observed land use change. An EC-based hydrograph separation method allowed estimating the groundwater contribution to 104 stormflow events. Mean soil surface crusting rates corresponding to each of the nine land uses identified in the catchment were determined using 236 standard 1-m2 micro-plots. Mean plant cover for each land use was assessed in 10 × 10-m2 plots. Bedrock topography and soil layers’ structure were assessed by electrical resistivity tomography to determine pathways of subsurface storm flows. Our results indicate that an increase in the catchment's areal percentage of fallow from 33% to 71% led to a decrease in the annual runoff coefficient from 43% to 26%. The concurrent reduction of soil crusting rate over the catchment, from 48% to 30%, increased rainwater infiltration. Consecutively, groundwater contribution to storm streamflow increased from 83% to 94%, highlighting the protective role of a dense vegetation cover against flash floods. The overall reduction of the annual basin water yield for inter-storm streamflow from 450 to 185 mm suggests that the potential gain in groundwater recharge was offset by the increased root water uptake for evapotranspiration, as confirmed by the drop in the groundwater level. This analysis illustrates how two different land uses with opposite impacts on soil permeability (i/ extensive soil surface crusting under annual crops resulting in limited runoff infiltration or ii/ fallow regrowth promoting both infiltration and evapotranspiration) both inhibit groundwater recharge. The maintenance of strips of fallow buffers between annual crop plots can slow down runoff and locally promote infiltration and groundwater recharge while limiting evapotranspiration.
Published: 2018
Full Text: View/download PDF

16. Vicinal land use change strongly drives stream bacterial community in a tropical montane catchment

Author: Olivier Ribolzi, Emma Rochelle-Newall, Bounsamay Soulileuth, Yves Auda, Thomas Pommier, Huong T. Le, Elisa Thébault, Oloth Sengtaheuanghoung, Laboratoire d'Ecologie Microbienne - UMR 5557 (LEM), Centre National de la Recherche Scientifique (CNRS)-Ecole Nationale Vétérinaire de Lyon (ENVL)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de la Recherche Agronomique (INRA)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS), Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Ecole Nationale Vétérinaire de Lyon (ENVL), French National Research Agency ANR-13-AGRO-0007, USTH, Vietnam, and IRD (ARTS)
Subjects: 0301 basic medicine, 010504 meteorology & atmospheric sciences, [SDV]Life Sciences [q-bio], Land management, Drainage basin, Biology, DOC, 01 natural sciences, Applied Microbiology and Biotechnology, Microbiology, LU legacy, 03 medical and health sciences, hyporheic zone, Rivers, Dissolved organic carbon, Hyporheic zone, Land use, land-use change and forestry, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Tropical Climate, geography, geography.geographical_feature_category, Bacteria, Ecology, Land use, bacterial diversity, land management, 15. Life on land, Carbon, 6. Clean water, Colored dissolved organic matter, 030104 developmental biology, 13. Climate action, CDOM, Seasons, Species richness
Abstract: International audience; Impact of land use (LU) change on stream environmental conditions and the inhabiting bacterial community remains rarely investigated, especially in tropical montane catchments. We examined the effects of LU change and its legacy along a tropical stream by comparing seasonal patterns of dissolved organic carbon (DOC) / colored dissolved organic matter (CDOM) in relation to variations in structure, diversity and metabolic capacities of particle-attached (PA) and free-living (FL) bacterial communities. We hypothesized that despite seasonal differences, hydrological flows that accumulate allochthonous carbon along the catchment are a major controlling factor of the bacterial community. Surprisingly, local environmental conditions that were largely related to nearby LU and the legacy of LU change were more important for stream bacterial diversity than hydrological connectivity. DOC was strongly correlated with PA richness and diversity. The legacy of LU change between teak plantation and annual crops induced high DOC and high diversity and richness of PA in the adjacent waters, while banana plantations were associated with high diversity of FL. The community structures of both PA and FL differed significantly between seasons. Our results highlight the importance of vicinal LU change and its legacy on aquatic bacterial communities in mixed used tropical watersheds.
Published: 2018
Full Text: View/download PDF

17. Field and modelling studies of Escherichia coli loads in tropical streams of montane agro-ecosystems

Author: Xaypaseuth Olasa, Keo Oudone Latsachak, Olivier Ribolzi, Emma Rochelle-Newall, Chanthamousone Thammahacksa, Josette Garnier, Bounsamay Soulileuth, Thierry Henri-des-Tureaux, Oloth Sengtaheuanghoung, Jean Causse, Gilles Billen, École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL), Centre National de la Recherche Scientifique (CNRS), Institut d'écologie et des sciences de l'environnement de Paris (iEES), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Recherche Agronomique (INRA), National University of Laos, Institut de Recherche pour le Développement, Partenaires INRAE, National Agriculture and Forestry Research Institute (NAFRI), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, GIS-Climat, Federation Ile-de-France de Recherche en Environnement [FIRE-FR3020], Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), École Pratique des Hautes Études (EPHE), and Université de Toulouse (UT)
Subjects: Environmental Engineering, Watershed, [SDV]Life Sciences [q-bio], Faecal indicator bacteria, STREAMS, Management, Monitoring, Policy and Law, Escherichia colt, Modelling, Tributary, Escherichia coli, Environmental Chemistry, Ecosystem, Water Science and Technology, Civil and Structural Engineering, Hydrology, geography, geography.geographical_feature_category, Discharge, 15. Life on land, Contamination, Microbiological water quality, Rural watershed, 6. Clean water, 13. Climate action, Soil water, Environmental science, Stormflow, Surface runoff
Abstract: International audience; The extent of faecal contamination in soils and water is still poorly known in rural tropical areas despite its important consequences on both human health and the economy. Here we explore the sources, pathways, and spatio-temporal dynamic of contamination in rivers of a rural tropical area at different spatial and temporal scales. Concentrations of Escherichia coli (E. coli), a faecal indicator bacteria (FIB), were measured in the Nam Khan river, tributary of the Mekong river (North Lao PDR). Measurements were made from the headwaters to the main stream under contrasted hydrological conditions (i.e. during base flow and stormflow) and during the wet and dry seasons in 2011. The results show that E. coli contamination is controlled by both land use (i.e. stock of bacteria brought to the soil surface by the faeces of human and livestock) and hydrology (i.e. contribution of overland flow to the river discharge). Direct point-source contamination is of minor importance in this rural watershed, however, during high discharge the concentration of FIB frequently exceeds 5000 MPN 100 mL(-1). The E. coli module of the Seneque/Riverstrahler model was adapted to the context of the Nam Khan river, validated with field observations and used to analyse future scenarios of faecal contamination (changing demographic trends and improvements in wastewater management). We found that the risk of worsening FIB contamination was more related to the predicted future rural exodus and to wastewater management practices rather than to an increase in demographic pressure in these upland systems.
Published: 2015
Full Text: View/download PDF

18. Hydrological modeling of Fecal Indicator Bacteria in a tropical mountain catchment

Author: Laurie Boithias, Norbert Silvera, Olivier Ribolzi, Keooudone Latsachack, Kyung Hwa Cho, Chanthamousone Thammahacksa, Oloth Sengtaheuanghoung, Alain Pierret, Emma Rochelle-Newall, Minjeong Kim, Yakov Pachepsky, School of Urban and Environmental Engineering, UNIST The Genomics Institute, Géosciences Environnement Toulouse (GET), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES), Université Fédérale Toulouse Midi-Pyrénées, Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Centre National d'Études Spatiales [Toulouse] (CNES), Department of Agricultural Land Management (DALaM), Institut de Recherche pour le Développement (IRD [France-Ouest]), Institut d'écologie et des sciences de l'environnement de Paris (IEES), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Recherche Agronomique (INRA), Département of Agricultural Land Management (DALam), Environmental Microbial and Food Safety Laborator, USDA-ARS : Agricultural Research Service, Lao Department of Agricultural Land Management (DALaM), MSEC project (Multi-Scale Environment Changes), French National Research Agency (TecItEasy project) [ANR-13-AGRO-0007], Basic Core Technology Development Program for the Oceans, Polar Regions of the National Research Foundation (NRF) - Ministry of Science, ICT AMP, Future Planning [NRF-2016M1A5A1027457], Research Institute for Development (IRD) (Accueil de post-doctorants/Campagne), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Department of Agricultural Land Management [Vientiane] (DALaM), Ministry of Agriculture and Forestry of Laos, Institut d'écologie et des sciences de l'environnement de Paris (iEES), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-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), and Université de Toulouse (UT)
Subjects: Wet season, Environmental Engineering, [SDV]Life Sciences [q-bio], 0208 environmental biotechnology, Indicator bacteria, 02 engineering and technology, Fecal Indicator Organism, Fate and transport, Deposition (geology), Feces, Dry season, Escherichia coli, SWAT, SWAT model, Tropical watershed, Waste Management and Disposal, Water Science and Technology, Civil and Structural Engineering, Hydrology, Tropical Climate, Baseflow, Bacteria, Ecological Modeling, Environmental engineering, Sediment, Soil and Water Assessment Tool, Pollution, 6. Clean water, 020801 environmental engineering, 13. Climate action, Laos, Environmental science, Water Microbiology, Surface water, Environmental Monitoring
Abstract: The occurrence of pathogen bacteria in surface waters is a threat to public health worldwide. In particular, inadequate sanitation resulting in high contamination of surface water with pathogens of fecal origin is a serious issue in developing countries such as Lao P.D.R. Despite the health implications of the consumption of contaminated surface water, the environmental fate and transport of pathogens of fecal origin and their indicators (Fecal Indicator Bacteria or FIB) are still poorly known in tropical areas. In this study, we used measurements of flow rates, suspended sediments and of the FIB Escherichia coli (E. coli) in a 60-ha catchment in Northern Laos to explore the ability of the Soil and Water Assessment Tool (SWAT) to simulate watershed-scale FIB fate and transport. We assessed the influences of 3 in-stream processes, namely bacteria deposition and resuspension, bacterial regrowth, and hyporheic exchange (i.e. transient storage) on predicted FIB numbers. We showed that the SWAT model in its original version does not correctly simulate small E. coli numbers during the dry season. We showed that model's performance could be improved when considering the release of E. coli together with sediment resuspension. We demonstrated that the hyporheic exchange of bacteria across the Sediment-Water Interface (SWI) should be considered when simulating FIB concentration not only during wet weather, but also during the dry season, or baseflow period. In contrast, the implementation of the regrowth process did not improve the model during the dry season without inducing an overestimation during the wet season. This work thus underlines the importance of taking into account in-stream processes, such as deposition and resuspension, regrowth and hyporheic exchange, when using SWAT to simulate FIB dynamics in surface waters.
Published: 2017
Full Text: View/download PDF

19. Organic and Clay-Based Soil Amendments Increase Maize Yield, Total Nutrient Uptake, and Soil Properties in Lao PDR

Author: Nivong Sipaseuth, Andrew Noble, Wolde Mekuria, Deborah A. Bossio, Chu Thai Hoanh, Oloth Sengtaheuanghoung, Simon J. Langan, and Matthew McCartney
Subjects: Renewable Energy, Sustainability and the Environment, Compost, Randomized block design, Development, engineering.material, Husk, Crop, Soil conditioner, Nutrient, Agronomy, Biochar, engineering, Environmental science, Soil fertility, Agronomy and Crop Science
Abstract: In the Lao People’s Democratic Republic (PDR), increasing food security remains a challenge since smallholder agricultural systems, which are the main source of food production, are under serious threat due to poor soil fertility and climate variability. This study was undertaken in Lao PDR to investigate the impacts of organic and clay-based soil amendments on maize yield, total nutrient uptake, and soil properties. Structured field experiments were established over two consecutive years (2011 and 2012) with maize as the test crop at the Veunkham and Naphok sites. Ten treatments were applied in a randomized complete block design with three replications. The treatments were control, rice husk biochar (applied at a rate of 10 t ha−1), bentonite clay (10 t ha−1), compost (4 t ha−1), clay-manure compost (10 t ha−1), rice husk biochar compost (10 t ha−1), and their combinations. All treatments were applied in 2011. Significant (p < 0.05) treatment effects in maize grain yields, total nutrient uptake, and soil...
Published: 2014
Full Text: View/download PDF

20. Combining multiple fallout radionuclides (137Cs, 7Be, 210Pbxs) to investigate temporal sediment source dynamics in tropical, ephemeral riverine systems

Author: Irène Lefèvre, Sylvain Huon, Oloth Sengtaheuanghoung, Olivier Ribolzi, J. Patrick Laceby, Olivier Evrard, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Géochimie Des Impacts (GEDI), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut d'écologie et des sciences de l'environnement de Paris (iEES), Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Department of Agricultural Land Management (DALaM), Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), 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), Lao Department of Agriculture Land Management (DALam), Multi-Scale Environment Changes (MSEC) project, French Centre National de la Recherche Scientifique EC2CO/BIOHEFECT, French National Research Agency [ANR-13-AGRO-0007], ANR-13-AGRO-0007,TecItEasy,Effets conjugués de l'expansion des plantations d'arbres et du changement climatique sur le fonctionnement hydro-sédimentaire des bassins versants tropicaux de montagne: la diversité microbienne aquatique comme un proxy de la conversion d'usage des terres(2013), Patrimoines Locaux et Gouvernance (PALOC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), Institut d'écologie et des sciences de l'environnement de Paris (IEES), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Recherche Agronomique (INRA), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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)
Subjects: Caesium-137, 010504 meteorology & atmospheric sciences, Stratigraphy, Drainage basin, Sediment tracing, 010501 environmental sciences, [SDV.SA.SDS]Life Sciences [q-bio]/Agricultural sciences/Soil study, 01 natural sciences, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Fingerprinting, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Subsoil, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Earth-Surface Processes, Hydrology, Beryllium-7, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Radionuclide, geography, geography.geographical_feature_category, Ephemeral key, Sampling (statistics), Sediment, 15. Life on land, 6. Clean water, 13. Climate action, Laos, Lead-210, Environmental science, Soil conservation
Abstract: International audience; Land use change and the associated acceleration of soil erosion have increased sediment supply to rivers worldwide. To effectively manage sediment loads, it is important to understand sediment dynamics. Fallout radionuclides (i.e. Be-7, excess Pb-210, Cs-137) separately provide spatial and temporal sediment source information. However, their combined application has been limited by an assumption that subsurface sources do not receive Be-7 fallout. Here, we examine this assumption and investigate the utility of combining these radionuclides to simultaneously model spatial and temporal sediment source dynamics. Soil and subsurface material were sampled to characterize potential sediment sources in a 12-km(2) catchment in northern Laos. This included material that was directly sampled from surface and subsurface sources (n = 65) and also in situ sediment source samples that were collected in ephemeral flow on hillslopes (n = 19). Suspended sediment (n = 16) was sampled at two monitoring stations. A distribution modelling approach quantified the relative contributions of surface and subsurface sources, as well as the proportion of material labelled with Be-7. The results from these two end-member models were compared to a four end-member model examining contributions from recently eroded surface, recently eroded subsurface, re-suspended surface and re-suspended subsurface sources. Approximately 80 % of sediment was modelled to be supplied by sources labelled with Be-7. Subsurface sources were modelled to contribute similar to 75 % of sediment. Accordingly, there was similar to 55 % more sediment modelled from subsurface sources than expected if subsurface sources were sheltered from Be-7 fallout. Differences between subsoil and Be-7-labelled source contributions modelled by the two and four end-member models were, with one exception (0.3 %), within the range of model uncertainty, further supporting the existence of re-suspended subsurface sources. At an upstream sampling location (S4), surface sources contributed the majority of sediment (55 %) whereas subsurface sources dominated the supply of sediment downstream (S10-74 %). Importantly, re-suspended subsurface sources, labelled with Be-7, were a significant sediment source at the catchment outlet (S10-60 %) during the investigated event. This study demonstrates the utility of combining multiple radionuclides when investigating spatial and temporal sediment source dynamics in tropical, ephemeral catchments. In the future, this approach should be tested with larger source datasets during the entire wet season and in larger catchments. This research furthers our understanding of sediment propagation in tropical catchments, contributing to the implementation of efficient soil conservation measures to reduce the deleterious effects of suspended sediment loads.
Published: 2016
Full Text: View/download PDF

21. Use of fallout radionuclides (7Be, 210Pb) to estimate resuspension of Escherichia coli from streambed sediments during floods in a tropical montane catchment

Author: Norbert Silvera, Emma Rochelle-Newall, Oloth Sengtaheuanghoung, Chanthamousone Thammahacksac, Olivier Evrard, Thierry Henri-des-Tureaux, Olivier Ribolzi, Sylvain Huon, Géosciences Environnement Toulouse (GET), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Géochimie Des Impacts (GEDI), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut d'écologie et des sciences de l'environnement de Paris (iEES), Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD), Department of Agricultural Land Management (DALaM), Lao Department of Agriculture Land Management (DALAM), MSEC project (Multi-Scale Environment Changes), French Centre National de la Recherche Scientifique EC2CO/BIOHEFECT program (Belcrue project), French Centre National de la Recherche Scientifique EC2CO/BIOHEFECT program (Belkong project), French National Research Agency [ANR-13-AGRO-0007], ANR-13-AGRO-0007,TecItEasy,Effets conjugués de l'expansion des plantations d'arbres et du changement climatique sur le fonctionnement hydro-sédimentaire des bassins versants tropicaux de montagne: la diversité microbienne aquatique comme un proxy de la conversion d'usage des terres(2013), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES), Patrimoines Locaux et Gouvernance (PALOC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD), Institut d'écologie et des sciences de l'environnement de Paris (IEES), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Recherche Agronomique (INRA), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), 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), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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)
Subjects: Radioactive Fallout, Geologic Sediments, Water flow, Rain, Health, Toxicology and Mutagenesis, 0208 environmental biotechnology, Hydrograph, 02 engineering and technology, STREAMS, 010501 environmental sciences, South East Asia, 01 natural sciences, Feces, Overland flow, FIB, Rivers, Streamflow, Escherichia coli, Hydrological modelling, Environmental Chemistry, Water Pollutants, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Radioisotopes, Hydrology, Beryllium-7, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Tropical Climate, General Medicine, 15. Life on land, Pollution, [SDV.MP.BAC]Life Sciences [q-bio]/Microbiology and Parasitology/Bacteriology, Floods, 6. Clean water, 020801 environmental engineering, Lead, 13. Climate action, Erosion, Lead-210, Land use, Beryllium, Surface runoff, Geology, Groundwater, Environmental Monitoring, Return flow
Abstract: Consumption of water polluted by faecal contaminants is responsible for 2 million deaths annually, most of which occur in developing countries without adequate sanitation. In tropical aquatic systems, streambeds can be reservoirs of persistent pathogenic bacteria and high rainfall can lead to contaminated soils entering streams and to the resuspension of sediment-bound microbes in the streambed. Here, we present a novel method using fallout radionuclides ((7)Be and (210)Pbxs) to estimate the proportions of Escherichia coli, an indicator of faecal contamination, associated with recently eroded soil particles and with the resuspension of streambed sediments. We show that using these radionuclides and hydrograph separations we are able to characterize the proportion of particles originating from highly contaminated soils and that from the resuspension of particle-attached bacteria within the streambed. We also found that although overland flow represented just over one tenth of the total flood volume, it was responsible for more than two thirds of the downstream transfer of E. coli. We propose that data obtained using this method can be used to understand the dynamics of faecal indicator bacteria (FIB) in streams thereby providing information for adapted management plans that reduce the health risks to local populations. Graphical Abstract Graphical abstract showing (1) the main water flow processes (i.e. overland flow, groundwater return flow, blue arrows) and sediment flow components (i.e. resuspension and soil erosion, black arrows) during floods in the Houay Pano catchment; (2) the general principle of the method using fallout radionuclide markers (i.e. (7)Be and (210)Pbxs) to estimate E. coli load from the two main sources (i.e. streambed resuspension vs soil surface washoff); and 3) the main results obtained during the 15 May 2012 storm event (i.e. relative percentage contribution of each process to the total streamflow, values in parentheses).
Published: 2016
Full Text: View/download PDF

22. Contradictory hydrological impacts of afforestation in the humid tropics evidenced by long-term field monitoring and simulation modelling

Author: Didier Orange, Olivier Ribolzi, Jean-Louis Janeau, Henri Robain, Alain Pierret, Christian Valentin, Guillaume Lacombe, Toan Tran Duc, Keoudone Latsachak, Adrien Taccoen, Rinh Pham Dinh, Anneke de Rouw, Phouthamaly Sengphaathith, Emmanuel Mouche, Norbert Silvera, Bounsamai Soulileuth, Oloth Sengtaheuanghoung, International Water Management Institute [CGIAR, Laos] (IWMI), International Water Management Institute [CGIAR, Sri Lanka] (IWMI), Consultative Group on International Agricultural Research [CGIAR] (CGIAR)-Consultative Group on International Agricultural Research [CGIAR] (CGIAR), Géosciences Environnement Toulouse (GET), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Institut d'écologie et des sciences de l'environnement de Paris (iEES Paris ), Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Soils and Fertilizers Research Institute (SFRI), Vietnam Academy of Agricultural Sciences (VAAS), Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA), Laboratoire d'Etudes des Ressources Forêt-Bois (LERFoB), Ecole Nationale du Génie Rural, des Eaux et des Forêts (ENGREF)-Institut National de la Recherche Agronomique (INRA), University of Arizona, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Modélisation Hydrologique (HYDRO), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Ministry of Agriculture and Forestry of Laos, Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), 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), Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Géosciences Environnement Toulouse ( GET ), Institut de Recherche pour le Développement ( IRD ) -Université Paul Sabatier - Toulouse 3 ( UPS ) -Observatoire Midi-Pyrénées ( OMP ) -Centre National de la Recherche Scientifique ( CNRS ), Institut d'écologie et des sciences de l'environnement de Paris ( IEES ), Institut National de la Recherche Agronomique ( INRA ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Université Paris-Est Créteil Val-de-Marne - Paris 12 ( UPEC UP12 ) -Centre National de la Recherche Scientifique ( CNRS ), Institut de Recherche pour le Développement ( IRD [France-Ouest] ), Centre de Recherches Interculturelles sur les Domaines Anglophones et Francophones ( CRIDAF ), Université Paris 13 ( UP13 ) -Université Sorbonne Paris Cité ( USPC ), Laboratory of Molecular Neuro-oncology, Howard Hughes Medical Institute ( HHMI ) -The Rockefeller University, Representation du Laos ( IRD ), Unité GEOVAST, Institut de Recherche pour le Développement ( IRD ), Laboratoire de minéralogie, cristallographie de Paris ( LMCP ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -IPG PARIS-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] ( LSCE ), Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université Paris-Saclay-Centre National de la Recherche Scientifique ( CNRS ), Department of Agricultural Land Management ( DALaM ), Soils and Fertilizers Research Institute ( SFRI ), VAAS, Laboratoire Chrono-environnement ( LCE ), Université Bourgogne Franche-Comté ( UBFC ) -Université de Franche-Comté ( UFC ) -Centre National de la Recherche Scientifique ( CNRS ), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Institut d'écologie et des sciences de l'environnement de Paris (IEES), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Recherche Agronomique (INRA), Institut de Recherche pour le Développement (IRD [France-Ouest]), Centre de Recherches Interculturelles sur les Domaines Anglophones et Francophones (CRIDAF), Université Paris 13 (UP13)-Université Sorbonne Paris Cité (USPC), Howard Hugues Medical Institute-The Rockefeller University, Representation du Laos (IRD), Institut de Recherche pour le Développement (IRD), Laboratoire de minéralogie, cristallographie de Paris (LMCP), Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), Department of Agricultural Land Management (DALaM), Laboratoire Chrono-environnement - UFC (UMR 6249) (LCE), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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)
Subjects: [ SDU.OCEAN ] Sciences of the Universe [physics]/Ocean, Atmosphere, 010504 meteorology & atmospheric sciences, Tree planting, 0208 environmental biotechnology, Conservation des sols, 02 engineering and technology, 01 natural sciences, lcsh:Technology, Water balance, Shifting cultivation, Tectona grandis, Afforestation, Forêt tropicale humide, lcsh:Environmental technology. Sanitary engineering, Hydrologie, ComputingMilieux_MISCELLANEOUS, lcsh:Environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, 2. Zero hunger, lcsh:GE1-350, lcsh:Geography. Anthropology. Recreation, Plantation forestière, Reconstitution forestière, lcsh:TD1-1066, Water conservation, Conservation de l'eau, Streamflow, [ SDU.ENVI ] Sciences of the Universe [physics]/Continental interfaces, environment, Hydrometeorology, P10 - Ressources en eau et leur gestion, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, 0105 earth and related environmental sciences, P36 - Érosion, conservation et récupération des sols, Hydrology, lcsh:T, Régénération naturelle, 15. Life on land, K10 - Production forestière, 020801 environmental engineering, Water resources, lcsh:G, 13. Climate action, Environmental science
Abstract: The humid tropics are exposed to an unprecedented modernisation of agriculture involving rapid and mixed land-use changes with contrasted environmental impacts. Afforestation is often mentioned as an unambiguous solution for restoring ecosystem services and enhancing biodiversity. One consequence of afforestation is the alteration of streamflow variability which controls habitats, water resources, and flood risks. We demonstrate that afforestation by tree planting or by natural forest regeneration can induce opposite hydrological changes. An observatory including long-term field measurements of fine-scale land-use mosaics and of hydrometeorological variables has been operating in several headwater catchments in tropical southeast Asia since 2000. The GR2M water balance model, repeatedly calibrated over successive 1-year periods and used in simulation mode with the same year of rainfall input, allowed the hydrological effect of land-use change to be isolated from that of rainfall variability in two of these catchments in Laos and Vietnam. Visual inspection of hydrographs, correlation analyses, and trend detection tests allowed causality between land-use changes and changes in seasonal streamflow to be ascertained. In Laos, the combination of shifting cultivation system (alternation of rice and fallow) and the gradual increase of teak tree plantations replacing fallow led to intricate streamflow patterns: pluri-annual streamflow cycles induced by the shifting system, on top of a gradual streamflow increase over years caused by the spread of the plantations. In Vietnam, the abandonment of continuously cropped areas combined with patches of mix-trees plantations led to the natural re-growth of forest communities followed by a gradual drop in streamflow. Soil infiltrability controlled by surface crusting is the predominant process explaining why two modes of afforestation (natural regeneration vs. planting) led to opposite changes in streamflow regime. Given that commercial tree plantations will continue to expand in the humid tropics, careful consideration is needed before attributing to them positive effects on water and soil conservation.
Published: 2016
Full Text: View/download PDF

23. Land use and soil type determine the presence of the pathogen Burkholderia pseudomallei in tropical rivers

Author: Olivier Ribolzi, Bounsamai Soulileuth, David A. B. Dance, Sabine Dittrich, Yves Auda, Emma Rochelle-Newall, Alain Pierret, Sayaphet Rattanavong, Oloth Sengtaheuanghoung, Michael Knappik, Paul N. Newton, Géosciences Environnement Toulouse (GET), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Institut d'Ecologie et des Sciences de l'Environnement de Paris (IEES Paris), University of Oxford [Oxford], Mahosot Hospital, Institut de Recherche pour le Développement, Partenaires INRAE, Département of Agricultural Land Management (DALam), Inst Ecol & Environm Sci Paris, Inst Rech Dev, Viangchan, Laos, Institut de Recherche pour le Developpement (IRD) through the regional pilot program Soils, Waters, Coastal Zones and Societies in Southern and Southeast Asia (SELTAR-RPP), French ANR 'Teciteasy', French Institut de Recherche pour le Developpement (IRD) [ANR-13-AGRO-0007], Wellcome Trust of Great Britain, Lee Ka Shing Foundation of the University of Oxford [SM40], 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Institut d'écologie et des sciences de l'environnement de Paris (iEES Paris ), and Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
Subjects: 0301 basic medicine, Watershed, Melioidosis, Burkholderia pseudomallei, Health, Toxicology and Mutagenesis, [SDV]Life Sciences [q-bio], 030106 microbiology, Acrisols, Biology, South East Asia, Real-Time Polymerase Chain Reaction, Enrichment culture, 03 medical and health sciences, Soil, Rivers, Turbidity of river water, Tropical climate, medicine, Humans, Environmental Chemistry, Soil Microbiology, Tropical Climate, Ecology, Geographical information system (GIS), Tropics, General Medicine, 15. Life on land, biochemical phenomena, metabolism, and nutrition, Partial least squares discriminant analysis (PLSDA), medicine.disease, Soil type, biology.organism_classification, bacterial infections and mycoses, Pollution, 6. Clean water, bacteria, Ferralsols, Soil microbiology, Research Article
Abstract: International audience; Burkholderia pseudomallei is the bacterium that causes melioidosis in humans. While B. pseudomallei is known to be endemic in South East Asia (SEA), the occurrence of the disease in other parts of the tropics points towards a potentially large global distribution. We investigated the environmental factors that influence the presence (and absence) of B. pseudomallei in a tropical watershed in SEA. Our main objective was to determine whether there is a link between the presence of the organism in the hydrographic network and the upstream soil and land-use type. The presence of B. pseudomallei was determined using a specific quantitative real-time PCR assay following enrichment culture. Land use, soil, geomorphology, and environmental data were then analyzed using partial least squares discriminant analysis (PLSDA) to compare the B. pseudomallei positive and negative sites. Soil type in the surrounding catchment and turbidity had a strong positive influence on the presence (acrisols and luvisols) or absence (ferralsols) of B. pseudomallei. Given the strong apparent links between soil characteristics, water turbidity, and the presence/absence of B. pseudomallei, actions to raise public awareness about factors increasing the risk of exposure should be undertaken in order to reduce the incidence of melioidosis in regions of endemicity.
Published: 2016
Full Text: View/download PDF

24. Economic contribution and the potential use of wood charcoal for soil restoration: a case study of village-based charcoal production in Central Laos

Author: Oloth Sengtaheuanghoung, Wolde Mekuria, Andrew Noble, and Chu Thai Hoanh
Subjects: Agroforestry, Geography, Planning and Development, Management, Monitoring, Policy and Law, Overexploitation, Land reclamation, Deforestation, visual_art, visual_art.visual_art_medium, Production (economics), Environmental science, Economic contribution, Soil restoration, Forest degradation, Charcoal
Abstract: Wood charcoal production provides affordable energy in many developing countries and has substantially contributed to the economy through the provision of rural incomes. In several countries, charcoal production leads to overexploitation of forests due to inefficiencies in processing. This study was undertaken in central Laos to (1) examine and document traditional charcoal production systems; (2) investigate the production capacity, recovery efficiencies and economic gains of existing traditional charcoal production methods; (3) characterize the chemical properties of wood charcoal and investigate the potential for soil restoration and (4) investigate local charcoal producers' perception on forest degradation and their species preferences. Through a socio-economic survey, a cost-based method for economic valuation was undertaken on a range of charcoal production methods currently being used. Laboratory chemical analyses were performed on wood charcoal samples. Results indicated that the traditional mud c...
Published: 2012
Full Text: View/download PDF

25. Afforestation by natural regeneration or by tree planting: examples of opposite hydrological impacts evidenced by long-term field monitoring in the humid tropics

Author: Olivier Ribolzi, P. Sengphaathith, Alain Pierret, J.-L. Janeau, N. Silvera, Emmanuel Mouche, Didier Orange, K.O. Latsachak, Henri Robain, R. Pham Dinh, T. Tran Duc, Guillaume Lacombe, Bounsamay Soulileuth, A. de Rouw, Christian Valentin, Oloth Sengtaheuanghoung, and A. Taccoen
Subjects: Water conservation, Land use, Agroforestry, Tree planting, Environmental science, Afforestation, Soil conservation, Surface runoff, Term (time), Ecosystem services
Abstract: The humid tropics are exposed to an unprecedented modernization of agriculture involving rapid and highly-mixed land-use changes with contrasted environmental impacts. Afforestation is often mentioned as an unambiguous solution for restoring ecosystem services and enhancing biodiversity. One consequence of afforestation is the alteration of streamflow variability controlling habitats, water resources and flood risks. We demonstrate that afforestation by tree planting or by natural forest regeneration can induce opposite hydrological changes. An observatory including long-term field measurements of fine-scale land-use mosaics and of hydro-meteorological variables has been operating in several headwater catchments in tropical Southeast Asia since 2001. The GR2M water balance model repeatedly calibrated over successive 1 year periods, and used in simulation mode with specific rainfall input, allowed the hydrological effect of land-use change to be isolated from that of rainfall variability in two of these catchments in Laos and Vietnam. Visual inspection of hydrographs, correlation analyses and trend detection tests allowed causality between land-use changes and changes in seasonal flows to be ascertained. In Laos, the combination of shifting cultivation system (alternation of rice and fallow) and the gradual increase of teak tree plantations replacing fallow, led to intricate flow patterns: pluri-annual flow cycles induced by the shifting system, on top of a gradual flow increase over years caused by the spread of the plantation. In Vietnam, the abandonment of continuously cropped areas mixed with patches of tree plantations led to the natural re-growth of forest communities followed by a gradual drop in streamflow. Soil infiltrability controlled by surface crusting is the predominant process explaining why two modes of afforestation (natural regeneration or planting) led to opposite changes in flow regime. Given that commercial tree plantations will continue to expand in the humid tropics, careful consideration is needed before attributing to them positive effects on water and soil conservation.
Published: 2015
Full Text: View/download PDF

26. A short review of fecal indicator bacteria in tropical aquatic ecosystems: knowledge gaps and future directions

Author: Thi Phuong Quynh Le, Oloth Sengtaheuanghoung, Olivier Ribolzi, Emma Rochelle-Newall, Thi Mai Huong Nguyen, Institut d'écologie et des sciences de l'environnement de Paris (iEES), Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC), Vietnam Academy of Science and Technology (VAST), National Agriculture and Forestry Research Institute (NAFRI), Institut de Recherche pour le Développement (IRD), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Recherche Agronomique (INRA), and Rochelle Newall, Emma
Subjects: bactérie fécale, EROSION, Water flow, lcsh:QR1-502, ASSAINISSEMENT, BACTERIE, RISQUE SANITAIRE, Review, CULTURE DE MICROORGANISME, écosystème tropical, lcsh:Microbiology, hydrological modeling, LUMIERE, 2. Zero hunger, METHODE D'ANALYSE, education.field_of_study, PREDATION, Ecology, 6. Clean water, CONTAMINATION, INONDATION, FACTEUR CLIMATIQUE, DYNAMIQUE DE POPULATION, INDICATEUR ECOLOGIQUE, UTILISATION DU SOL, Microbiology (medical), EPIDEMIOLOGIE, Population, FACTEUR DE RISQUE, Indicator bacteria, Biology, millennium development goals, Microbiology, FACTEUR ANTHROPIQUE, FIB, Urbanization, Temperate climate, eau potable, education, Indicator organism, biotic and abiotic factors, EAU POTABLE, MATIERE ORGANIQUE, Environmental and Society, E. coli, Tropics, developing countries, PREVENTION SANITAIRE, 15. Life on land, MODELISATION, indicateur fécal, [SDE.ES]Environmental Sciences/Environmental and Society, Fecal coliform, écosystème aquatique, die-off rates, 13. Climate action, CHANGEMENT CLIMATIQUE, E.coli, Environnement et Société, AGENT PATHOGENE
Abstract: International audience; Given the high numbers of deaths and the debilitating nature of diseases caused by the use of unclean water it is imperative that we have an understanding of the factors that control the dispersion of water borne pathogens and their respective indicators. This is all the more important in developing countries where significant proportions of the population often have little or no access to clean drinking water supplies. Moreover, and notwithstanding the importance of these bacteria in terms of public health, at present little work exists on the persistence, transfer and proliferation of these pathogens and their respective indicator organisms e.g. fecal indicator bacteria (FIB) such as Escherichia coli and fecal coliforms in humid tropical systems, such as are found in South East Asia or in the tropical regions of Africa. Both FIB and the waterborne pathogens they are supposed to indicate are particularly susceptible to shifts in water flow and quality and the predicted increases in rainfall and floods due to climate change will only exacerbate the problems of contamination. This will be furthermore compounded by the increasing urbanization and agricultural intensification that developing regions are experiencing. Therefore, recognizing and understanding the link between human activities, natural process and microbial functioning and their ultimate impacts on human health are prerequisites for reducing the risks to the exposed populations. Most of the existing work in tropical systems has been based on the application of temperate indicator organisms, models and mechanisms regardless of their applicability or appropriateness for tropical environments. Here we present a short review on the factors that control FIB dynamics in temperate systems and discuss their applicability to tropical environments. We then highlight some of the knowledge gaps in order to stimulate future research in this field in the tropics.
Published: 2015
Full Text: View/download PDF

27. Backward waters, modern waters : Perception-Based Regional Mapping territory uses and water-related sanitary stakes in Luang Phabang area (Lao PDR)

Author: Sylvia Becerra, Bounsamai Soulileuth, Olivier Ribolzi, Phabvilay Sounyafong, Keoudone Latsachach, Oloth Sengtaheuanghoung, Eric Maire, Marine Jourdren, Mehdi Saqalli, Sylvie Guillerme, Nicolas Maestripieri, Louy Tammahuxsa, Géographie de l'environnement (GEODE), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Institut d'Etudes Politiques, Representation du Laos (IRD), NAFRI, National Agricultural and Forestry Research Institute, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), 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), Université Toulouse - Jean Jaurès (UT2J)-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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), 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: Distribution networks, Perception-Based Regional Mapping, media_common.quotation_subject, Geography, Planning and Development, LUCC, Unit (housing), Environmental protection, Perception, perception-based regional mapping, Mekong river, Environmental planning, General Environmental Science, media_common, Land use, health risk esposure, Forestry, Differential (mechanical device), [SHS.GEO]Humanities and Social Sciences/Geography, Sanitation cover, 15. Life on land, 6. Clean water, Geography, Homogeneous, Laos, Tourism, Leisure and Hospitality Management, Scale (social sciences), sanitation cover, Health risk exposure
Abstract: International audience; This paper examines the suitability of the PBRM, a mapping tool based on the perceptions of local stakeholders, for assessing the connection between land uses and health issues. The area, rural Laos around Luang Phabang city, between the Mekong River valley and mountains, seems to have overcome the formal territorial organization based on exposure risks towards an organization based on access to health and medical facilities. In addition, differential access to safe drinking water has been quite solved by the implementation of private can distribution networks. However, these rapid changes accentuate the social gap between well-connected lowlands and valleys on one hand, and mountain areas on the other hand, increasingly sidelined from this transition. Methodologically, PBRM method explores broader issues at a broader scale but does not give an easy access to non-spatial criteria. Plus, the limits of the SHUs (Spatial Homogeneous Unit) the PBRM establishes are geographically precise regarding topology but not spatiality. These results are action-oriented towards local and development-oriented issues.
Published: 2015
Full Text: View/download PDF

28. Suspended sediment dynamics in a Southeast Asian mountainous catchment: Combining river monitoring and fallout radionuclide tracers

Author: Oloth Sengtaheuanghoung, Irène Lefèvre, Jean-Louis Reyss, Sophie Ayrault, Elian Gourdin, Sylvain Huon, Olivier Evrard, Olivier Ribolzi, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Géochimie Des Impacts (GEDI), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut d'écologie et des sciences de l'environnement de Paris (iEES Paris ), Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Géosciences Environnement Toulouse (GET), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Océan et Interfaces (OCEANIS), Département of Agricultural Land Management (DALam), This work received financial support from the French CNRS EC2CO /628 BIOHEFECT programme (Belcrue project), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and 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)
Subjects: [SDE.MCG]Environmental Sciences/Global Changes, Drainage basin, Southeast asian, Flood, Rainwater harvesting, River monitoring, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Sedimentary budget, Water Science and Technology, Hydrology, Radionuclide, geography, geography.geographical_feature_category, Flood myth, Be-7, Storm, 15. Life on land, 6. Clean water, 13. Climate action, Cs-137, Suspended sediment, [SDE]Environmental Sciences, Unsupported Pb-210, Surface runoff, Geology
Abstract: Part B; International audience; Soil erosion is intense in mountainous tropical regions where heavy storms result in the supply of large quantities of sediment to rivers. The origin and dynamics of suspended sediment were analysed in a catchment located in northern Laos during the first erosive flood of the rainy season in May 2012. The catchment was equipped with 4 successive gauging stations (draining areas ranging 0.2–11.6 km$^2$). Fallout radionuclides (Beryllium-7 – $^7$Be, unsupported Pb-210 –$^{210}$Pb$_{xs}$, and Cesium-137 – $^{137}$Cs) were determined on rainfall, overland flow, stream water, suspended sediment, soil surface and subsurface samples (with $n$ = 3, 19, 75, 75, 65 and 14 respectively). Assumptions underpinning the $^7$Be-labelling method were validated by implementing experiments in the laboratory (i.e., rainwater $^7$Be sorption to soil particles) and in the field (i.e., $^7$Be:$^{210}$Pb$_{xs}$ activity ratio evolution in rainwater and related overland flow during a natural storm event). Radionuclide analyses provided a way to quantify variations in sediment dynamics and origin throughout the flood: (1) a proportion of recently eroded sediment (labelled by $^7$Be, and referred to as “fresh sediment”) ranging between $ca$. 8–35% in suspended loads; (2) higher contributions of fresh sediment at the beginning of the flood rising stage; (3) a progressive dilution of fresh sediment by particles remobilised from the riverbed/channel; (4) the dominance of particles originating from the soil surface (ca. 70–80% of total sediment load) in upper parts and a much larger contribution of subsurface material ($ca$. 64%) at the downstream station. The original contribution of 7Be-labelled particles derived from collapsed riverbanks to sediment export was also demonstrated. This pilot study supports the use of fallout $^7$Be and $^{210}$Pb$_{xs}$ in tropical catchments to constrain sediment dynamics. It also puts forward the need to better characterize the sources of sediment in order to avoid possible misinterpretations.
Published: 2014
Full Text: View/download PDF

29. Spatial and temporal variability of $^7$Be and $^{210}$Pb wet deposition during four successive monsoon storms in a catchment of northern Laos

Author: Sylvain Huon, E. Gourdin, Thierry Bariac, Jean-Louis Reyss, Sophie Ayrault, Olivier Evrard, Oloth Sengtaheuanghoung, Olivier Ribolzi, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Biogéochimie et écologie des milieux continentaux (Bioemco), 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), Océan et Interfaces (OCEANIS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), 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), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), 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)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Géochimie Des Impacts (GEDI), Institut d'écologie et des sciences de l'environnement de Paris (IEES (UMR_7618 / UMR_D_242 / UMR_A_1392 / UM_113) ), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Sorbonne Université (SU)-Université de Paris (UP), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES), Department of Agriculture Land Management (DALam), and National Agriculture and Forestry Research Institute (NAFRI)
Subjects: Radioactive Fallout, Geologic Sediments, Rain, Health, Toxicology and Mutagenesis, [SDE.MCG]Environmental Sciences/Global Changes, Drainage basin, Oxygen Isotopes, Monsoon, Panoply, Rainwater harvesting, Rivers, Radiation Monitoring, Environmental Chemistry, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Waste Management and Disposal, Scavenging, Radioisotopes, Hydrology, geography, Radionuclide, geography.geographical_feature_category, Lead Radioisotopes, General Medicine, Rainout, Pollution, Deposition (aerosol physics), Laos, 13. Climate action, [SDE]Environmental Sciences, Environmental science, Beryllium, Water vapor
Abstract: International audience; Fallout radionuclides $^7$Be and $^{210}$Pb have been identified as potentially relevant temporal tracers for studying soil particles dynamics (surface vs. subsurface sources contribution; remobilization of in-channel sediment) during erosive events in river catchments. An increasing number of studies compared $^7$Be: $^{210}$Pb activity ratio in rainwater and sediment to estimate percentages of freshly eroded particles. However, the lack of data regarding the spatial and temporal variability of radionuclide wet deposition during individual storms has been identified as one of the main gaps in these estimates. In order to determine these key parameters, rainwater samples were collected at three stations during four storms that occurred at the beginning of the monsoon (June 2013) in the Houay Xon mountainous catchment in northern Laos. Rainwater $^7$Be and $^{210}$Pb activities measured using very low background hyperpure Germanium detectors ranged from 0.05 to 1.72 Bq L$^{−1}$ and 0.02 to 0.26 Bq L$^{−1}$, respectively. Water $\delta$18O were determined on the same samples. Total rainfall amount of the four sampled storms ranged from 4.8 to 26.4 mm (51 mm in total) at the time-fractionated collection point. Corresponding cumulative $^7$Be and $^{210}$Pb wet depositions during the sampling period were 17.6 and 2.9 Bq m$^{-2}$, respectively. The $^7$Be: $^{210}$Pb activity ratio varied (1) in space from 6 to 9 for daily deposition and (2) in time from 3 to 12 for samples successively collected. Intra-event evolution of rainwater $^7$Be and $^{210}$Pb activities as well as $\delta$18O highlighted the progressive depletion of local infra-cloud atmosphere radionuclide stock with time (washout), which remains consistent with a Raleigh-type distillation process for water vapour. Intra-storm ratio increasing with time showed the increasing contribution of rainout scavenging. Implications of such variability for soil particle labelling and erosion studies are briefly discussed and recommendations are formulated for the collection of rainwater signature in studies based on the $^7$Be: $^{210}$Pb ratio method, especially in tropical areas under high erosive pressure.
Published: 2014
Full Text: View/download PDF

30. Long-term soil carbon loss and accumulation in a catchment following the conversion of forest to arable land in northern Laos

Author: Pascal Podwojewski, Oloth Sengtaheuanghoung, Henri Robain, Anneke de Rouw, Cyril Girardin, Sylvain Huon, Philippe Bonté, Irène Lefèvre, Yann Le Troquer, Christian Valentin, Institut d'écologie et des sciences de l'environnement de Paris (IEES), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Recherche Agronomique (INRA), 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), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), Environnement et Grandes Cultures (EGC), AgroParisTech-Institut National de la Recherche Agronomique (INRA), National Agriculture and Forestry Research Institute (NAFRI), Institut d'écologie et des sciences de l'environnement de Paris (iEES), Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), 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 Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Géochimie Des Impacts (GEDI), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)
Subjects: 010504 meteorology & atmospheric sciences, [SDV]Life Sciences [q-bio], RESISTIVITE, Wetland, [SDV.SA.SDS]Life Sciences [q-bio]/Agricultural sciences/Soil study, SEDIMENT, 01 natural sciences, Swamp, Shifting cultivation, ALTITUDE, Deforestation, DEGRADATION DU SOL, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, ANALYSE ISOTOPIQUE, TOMOGRAPHIE, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, 0105 earth and related environmental sciences, 2. Zero hunger, Total organic carbon, Hydrology, geography, geography.geographical_feature_category, Ecology, Agroforestry, 04 agricultural and veterinary sciences, Soil carbon, 15. Life on land, RIZICULTURE, JACHERE, CARBONE ORGANIQUE, BASSIN VERSANT, Soil water, [SDE]Environmental Sciences, 040103 agronomy & agriculture, PENTE, 0401 agriculture, forestry, and fisheries, Environmental science, BRULIS, Animal Science and Zoology, EROSION HYDRIQUE, DEFORESTATION, Arable land, Agronomy and Crop Science, VARIATION PLURIANNUELLE, ZONE DE MONTAGNE
Abstract: Quantifying the magnitude of soil organic carbon loss linked to the conversion of forest to arable land in tropical environments requires long-term estimates of soil redistribution trends within the catchment. In order to assess the cumulative soil carbon loss that occurred since deforestation and cropping started in 1967, a multidisciplinary study was carried out in a small catchment (67 ha) with a swamp area in its middle part, characterized by steep slopes under shifting cultivation of upland rice, typical for northern Laos's landscapes. Using 137Cs and total organic carbon (TOC) inventories, it was possible to estimate a soil TOC depletion rate of 0.039 kgC m−2 yr−1 in 42 years (1963–2005), corresponding to ca. 21% of its initial content in the top 10 cm. Because farmers preferred clearing more fertile soils located downhill and leave forest on poorer soils on the crests, the redistribution of 137Cs and TOC along slopes of the catchment was mainly controlled by the topographic position of soils and the cultivation frequency. Estimates of soil TOC accumulation in wetlands with δ13C measurements and sediment volumes by electrical resistivity tomography showed that TOC accumulation rates were linked to land use change since the 1960s with three successive periods corresponding to undisturbed forest, deforestation-first rice crop and rice-fallow rotations. Forest clearing triggered a higher soil TOC delivery to the swamp (19.6 ± 5.5 kgC ha−1 yr−1) over 8 years (1967–1975) than the former undisturbed forest (8.5 ± 1.8 kgC ha−1 yr−1) and crop-fallow rotations over 30 years (1975–2005, 6.4 ± 4.8 kgC ha−1 yr−1). Due to the small size of the area covered by the swamp, only a limited fraction of eroded soil organic carbon (ca. 7 wt.%) was stored in wetlands of the catchment. Mineralization apparently played a key role for soil TOC depletion since first forest clearing.
Published: 2013
Full Text: View/download PDF

31. Impact of slope gradient on soil surface features and infiltration on steep slopes in northern Laos

Author: Jean-Pierre Thiébaux, Olivier Ribolzi, Christian Valentin, Oloth Sengtaheuanghoung, K.O. Latsachack, Emmanuel Mouche, L.M. Bresson, Norbert Silvera, J. Patin, Géosciences Environnement Toulouse (GET), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Environnement et Grandes Cultures (EGC), AgroParisTech-Institut National de la Recherche Agronomique (INRA), International Water Management Institute [CGIAR, Laos] (IWMI), International Water Management Institute [CGIAR, Sri Lanka] (IWMI), Consultative Group on International Agricultural Research [CGIAR] (CGIAR)-Consultative Group on International Agricultural Research [CGIAR] (CGIAR), Modélisation Hydrologique (HYDRO), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Agiculture Land Research Center (ALRC), National Agriculture and Forest Research Institute, Office of Science and Land Development, Institut de Recherche pour le Développement (IRD), Biogéochimie et écologie des milieux continentaux (Bioemco), 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), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), International Water Management Institute, 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), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-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), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), 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: [SDV.SA]Life Sciences [q-bio]/Agricultural sciences, 010504 meteorology & atmospheric sciences, Compaction, STEEP SLOPES, 01 natural sciences, Hydraulic conductivity, Hillslope processes, Vegetation and slope stability, 0105 earth and related environmental sciences, Earth-Surface Processes, Hydrology, RAINFALL SIMULATION, SURFACE DU SOL, HILLSLOPE PROCESSES, HYDROLOGIE, Infiltration, 04 agricultural and veterinary sciences, 15. Life on land, Runoff generation, Infiltration (HVAC), Bulk density, 6. Clean water, Steep slopes, INFILTRATION, Loam, Soil water, 040103 agronomy & agriculture, Rainfall simulation, 0401 agriculture, forestry, and fisheries, RUNOFF GENERATION, Surface runoff, Geology
Abstract: It was recently demonstrated that, infiltration into mountain-tilled soils with highly stable microaggregates, increases with increasing slope gradient. In this work we investigate the processes that underpin this phenomenon by means of field experiments and modelling. The study area is located in northern Laos. Rainfall simulations were conducted in two 1-m 2 plots using a portable field simulator. The drop size distribution and kinetic energy were similar to that occurring on the occasion of tropical downpours. Soils exhibited a clay loam texture and very similar organic matter contents across experimental plots, but differed greatly in slope gradient (30% and 75%). Runoff water samples were collected at intervals ranging from 1 to 3 min, depending on the runoff intensity. Plots microtopography was measured before and after rainfall simulations using an automatic surface roughness meter on a 1-cm grid. High-resolution bulk density images were obtained from soil slices using a standard X-ray generator. Final infiltration rates of 6 and 21 mm h −1 ; soil detachment of 667 and 310 g m −2 ; surface lowering due to soil loss of 0.82 and 0.38 mm; surface lowering due to compaction of 1.21 and 0.90 mm; percentage area with sieving crust of 36% and 90%; percentage area with erosion crust of 63% and 0%; were obtained for the 30% and 75% slopes, respectively. Three main conclusions can be drawn from this work: (1) high intensity rainfall can rapidly transform soil surface features of steep bare soil; (2) on steeper slopes, the micro-relief tends to form micro-terraces much more pervious and less erodible than the ripple-like roughness that formed on gentler slopes; and (3) there was a more pronounced lowering of the soil surface due to compaction and denser microlayers on gentler slopes. The latter conclusion confirms the hypothesis that higher effective rainfall intensity is responsible for the formation of less permeable erosion crusts under 30% slope gradients while more permeable structural crusts develop under 75% slope gradients. The runoff results were modelled with the Green and Ampt model which accounts for time evolution of soil hydraulic conductivity. This modelling shows that soil is undoubtedly non homogeneous, evolves with time and that infiltration kinetics is slower and soil permeability greater for the 75% slope.
Published: 2011
Full Text: View/download PDF

32. Land Use and Water Quality Along a Mekong Tributary in Northern Lao P.D.R

Author: Oloth Sengtaheuanghoung, Claire Mousquès, Alain Pierret, Olivier Ribolzi, Bounsamai Soulileuth, Juliette Cuny, Phonexay Sengsoulichanh, Sylvain Huon, Laboratoire des Mécanismes et Transfert en Géologie (LMTG), 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 de la Recherche Scientifique (CNRS), International Water Management Institute - South East Asia (IWMI-SEA), IWMI, NAFRI, National Agricultural and Forestry Research Institute, 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), Soil Survey and Land Classification Center (SSLCC), Ministry of Agriculture and Forestry, Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), 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), International Water Management Institute [CGIAR, Sri Lanka] (IWMI), Consultative Group on International Agricultural Research [CGIAR] (CGIAR)-Consultative Group on International Agricultural Research [CGIAR] (CGIAR), 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), 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), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)
Subjects: Rain, Population, 0207 environmental engineering, Drainage basin, Wetland, 02 engineering and technology, 010501 environmental sciences, Waste Disposal, Fluid, 01 natural sciences, Rivers, Surveys and Questionnaires, Tributary, Water Movements, Water Pollution, Chemical, 020701 environmental engineering, Water pollution, education, 0105 earth and related environmental sciences, Riparian zone, 2. Zero hunger, Hydrology, Global and Planetary Change, geography, education.field_of_study, geography.geographical_feature_category, Ecology, 1. No poverty, Agriculture, 15. Life on land, Pollution, Floods, 6. Clean water, Laos, 13. Climate action, Public Opinion, [SDE]Environmental Sciences, Environmental science, Water quality, Water Pollutants, Chemical, Environmental Monitoring, Waste disposal
Abstract: Improving access to clean water has the potential to make a major contribution toward poverty reduction in rural communities of Lao P.D.R. This study focuses on stream water quality along a Mekong basin tributary, the Houay Xon that flows within a mountainous, mosaic land-use catchment of northern Lao P.D.R. To compare direct water quality measurements to the perception of water quality within the riparian population, our survey included interviews of villagers. Water quality was found to vary greatly depending on the location along the stream. Overall, it reflected the balance between the stream self-cleaning potential and human pressure on the riparian zone: (i) high bacteria and suspended load levels occurred where livestock are left to free-range within the riparian zone; (ii) very low oxygen content and high bacteriological contamination prevailed downstream from villages; (iii) high concentrations of bacteria were consistently observed along urbanized banks; (iv) low oxygen content were associated with the discharge of organic-rich wastewater from a small industrial plant; (v) very high suspended load and bacteria levels occurred during flood events due to soil erosion from steep cultivated hill slopes. Besides these human induced pollutions we also noted spontaneous enrichments in metals in wetland areas fed by dysoxic groundwater. These biophysical measurements were in agreement with the opinions expressed by the majority of the interviewees who reported poor and decreasing water quality in the Houay Xon catchment. Based on our survey, we propose recommendations to improve or maintain stream water quality in the uplands of northern Lao P.D.R.
Published: 2010
Full Text: View/download PDF

33. Conflict, migration and land-cover changes in Indochina: a hydrological assessment

Author: Chu Thai Hoanh, Guillaume Lacombe, Alain Pierret, Andrew Noble, Oloth Sengtaheuanghoung, International Water Management Institute - South East Asia (IWMI-SEA), International Water Management Institute [CGIAR, Sri Lanka] (IWMI), Consultative Group on International Agricultural Research [CGIAR] (CGIAR)-Consultative Group on International Agricultural Research [CGIAR] (CGIAR), Soil Survey and Land Classification Center (SSLCC), Ministry of Agriculture and Forestry, 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), IWMI, 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: 010504 meteorology & atmospheric sciences, [SDV]Life Sciences [q-bio], 0207 environmental engineering, Drainage basin, evapotranspiration, 02 engineering and technology, Land cover, Aquatic Science, Structural basin, 01 natural sciences, forest, Deforestation, Agricultural land, land-cover, P10 - Ressources en eau et leur gestion, 020701 environmental engineering, Hydrologie, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, Earth-Surface Processes, Hydrology, Mekong, geography, geography.geographical_feature_category, Vietnam War, Ecology, Distribution spatiale, Changement de couvert végétal, Vegetation, 15. Life on land, F40 - Ecologie végétale, Évapotranspiration, Déboisement, 6. Clean water, Catchment hydrology, hydrological change, [SDE]Environmental Sciences, Surface runoff
Abstract: International audience; The Indochinese section of the Mekong Basin has been subjected to major environmental disturbances over the last half century. The Vietnam War is invoked as a central explanation for the extensive deforestation in specific areas while conflictinduced exoduses caused the abandonment of cultivated lands, followed by forest regeneration. Although the socio-economical consequences of these episodes have been analysed, their hydrological impacts remain unknown. This paper investigates hydrological changes in two catchments of the lower Mekong Basin that were either heavily bombed (in southern Laos) or depopulated (in northern Laos). This analysis is based on the widely and independently recognized fact that vegetation, via evapotranspiration, is a central driver of basin water yield. The analysis of the most complete Vietnam War air mission database and of available hydro-meteorological data over the period 1960–2004 reveals a sharp runoff increase in the southern catchment when bombing climaxed in the early 1970s while no hydrological change is observed in the northern catchment over the same period. From 1995 onwards, the northern and southern catchment's runoff productions are significantly lower and higher than in the pre-war conditions, respectively. Although causalities could not be ascertained because of data limitations, these short- and long-term hydrological shifts were found to be consistent, in terms of occurrence, spatial distribution and magnitude, with the expected changes in the vegetation cover, either denser in the north (in response to abandonment of cultivated lands) or sparser in the south (as a result of bomb-induced deforestation and soil degradations).
Published: 2010
Full Text: View/download PDF

34. Trapping efficiencies of cultivated and natural riparian vegetation of northern Laos

Author: Olga Vigiak, Oloth Sengtaheuanghoung, Christian Valentin, Olivier Ribolzi, Alain Pierret, International Water Management Institute - South East Asia (IWMI-SEA), IWMI, 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), MSEC, International Water Management Institute [CGIAR, Sri Lanka] (IWMI), Consultative Group on International Agricultural Research [CGIAR] (CGIAR)-Consultative Group on International Agricultural Research [CGIAR] (CGIAR), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), 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: Bamboo, Environmental Engineering, 010501 environmental sciences, Management, Monitoring, Policy and Law, Upland rice, [SDV.SA.SDS]Life Sciences [q-bio]/Agricultural sciences/Soil study, 01 natural sciences, Waste Management and Disposal, 0105 earth and related environmental sciences, Water Science and Technology, Riparian zone, 2. Zero hunger, Hydrology, geography, geography.geographical_feature_category, Sediment, food and beverages, Agriculture, 04 agricultural and veterinary sciences, Plants, 15. Life on land, Banana plantation, Pollution, 6. Clean water, Laos, 040103 agronomy & agriculture, Erosion, 0401 agriculture, forestry, and fisheries, Environmental science, Water quality, Surface runoff
Abstract: In northern Laos, intensification of cultivation on sloping land leads to accelerated erosion processes. Management of riparian land may counteract the negative impacts of higher sediment delivery rates on water quality. This study assessed water and sediment concentration trapping efficiencies of riparian vegetation in northern Laos and the effect of cultivation of riparian land on water quality. Runoff flowing in and out of selected riparian sites was monitored by means of open troughs. In 2005, two native grass, two bamboo, and two banana sites were monitored. In 2006, adjacent to steep banana, bamboo, and native grass sites, three upland rice sites were established and monitored. Water trapping efficiency (WTE) and sediment concentration trapping efficiency (SCTE) were calculated on an event basis; means and 95% confidence intervals (CIs) were estimated with a bootstrapping approach. Confidence intervals were large and overlapping among sites. Seepage conditions severely limited trapping efficiency. Native grass resulted in the highest WTE (95% CI, -0.10 to 0.23), which was not significantly different from zero. Banana resulted in the highest SCTE (95% CI, 0.06-0.40). Bamboo had negative WTE and SCTE. Median outflow runoff from rice sites was nine times the inflow. Median outflow sediment concentration from rice sites was two to five times that of their adjacent sites and two to five times the inflow sediment concentration. Although low-tillage banana plantation may reduce sediment concentration of runoff, cultivation of annual crops in riparian land leads to delivery of turbid runoff into the stream, thus severely affecting stream water quality.
Published: 2008
Full Text: View/download PDF

35. Interactions between root growth, slope and soil detachment depending on land use : a case study in a small mountain catchment of Northern Laos

Author: Alain Pierret, Keodoune Latchackak, Christian Valentin, Phouthone Chathanvongsa, and Oloth Sengtaheuanghoung
Subjects: Wet season, geography, geography.geographical_feature_category, Watershed, soil erosion, Agroforestry, Drainage basin, Soil Science, Plant Science, root length density, shifting cultivation, teak, Shifting cultivation, Infiltration (hydrology), Soil structure, Agronomy, Laos, Environmental science, Soil horizon, Surface runoff
Abstract: Roots modify the properties of soil in their immediate vicinity. Individually, fine roots (
Published: 2007

Catalog

Books, media, physical & digital resources

See catalog results

Searchworks

Select search scope, currently: Articles

Catalog

books, media & more in Jio Institute collections

Articles

journal articles & other e-resources

Refine your results

35 results on '"Oloth Sengtaheuanghoung"'

1. From shifting cultivation to teak plantation: effect on overland flow and sediment yield in a montane tropical catchment

2. Suspended sediment source and propagation during monsoon events across nested sub-catchments with contrasted land uses in Laos

3. Hydrological Regime and Water Shortage as Drivers of the Seasonal Incidence of Diarrheal Diseases in a Tropical Montane Environment.

4. Escherichia coli concentration, multiscale monitoring over the decade 2011–2021 in the Mekong River basin, Lao PDR

5. Escherichia coli concentration, multiscale monitoring over the decade 2011–2021 in the Mekong basin, Lao PDR

6. Experimental and modelling evidence of splash effects on manure borne Escherichia coli washoff

7. Linking tree-rooting profiles to leaf phenology: a first attempt on Tectona Grandis Linn F

8. The Multiscale <scp>TROPIcal CatchmentS</scp> critical zone observatory <scp>M‐TROPICS</scp> dataset <scp>II</scp> : Land use, hydrology and sediment production monitoring in Houay Pano, northern Lao <scp>PDR</scp>

9. Understorey vegetation drives surface runoff and soil loss in teak plantation-based system of Northern Laos

10. Linking crop structure, throughfall, soil surface conditions, runoff and soil detachment: 10 land uses analyzed in Northern Laos

11. Experimental and modelling evidence of short-term effect of raindrop impact on hydraulic conductivity and overland flow intensity

12. Quantifying the effect of overland flow on Escherichia coli pulses during floods: Use of a tracer-based approach in an erosion-prone tropical catchment

13. Understory Limits Surface Runoff and Soil Loss in Teak Tree Plantations of Northern Lao PDR

14. Modeling the Impact of Land Use Change on Basin-scale Transfer of Fecal Indicator Bacteria: SWAT Model Performance

15. Interacting land use and soil surface dynamics control groundwater outflow in a montane catchment of the lower Mekong basin

16. Vicinal land use change strongly drives stream bacterial community in a tropical montane catchment

17. Field and modelling studies of Escherichia coli loads in tropical streams of montane agro-ecosystems

18. Hydrological modeling of Fecal Indicator Bacteria in a tropical mountain catchment

19. Organic and Clay-Based Soil Amendments Increase Maize Yield, Total Nutrient Uptake, and Soil Properties in Lao PDR

20. Combining multiple fallout radionuclides (137Cs, 7Be, 210Pbxs) to investigate temporal sediment source dynamics in tropical, ephemeral riverine systems

21. Use of fallout radionuclides (7Be, 210Pb) to estimate resuspension of Escherichia coli from streambed sediments during floods in a tropical montane catchment

22. Contradictory hydrological impacts of afforestation in the humid tropics evidenced by long-term field monitoring and simulation modelling

23. Land use and soil type determine the presence of the pathogen Burkholderia pseudomallei in tropical rivers

24. Economic contribution and the potential use of wood charcoal for soil restoration: a case study of village-based charcoal production in Central Laos

25. Afforestation by natural regeneration or by tree planting: examples of opposite hydrological impacts evidenced by long-term field monitoring in the humid tropics

26. A short review of fecal indicator bacteria in tropical aquatic ecosystems: knowledge gaps and future directions

27. Backward waters, modern waters : Perception-Based Regional Mapping territory uses and water-related sanitary stakes in Luang Phabang area (Lao PDR)

28. Suspended sediment dynamics in a Southeast Asian mountainous catchment: Combining river monitoring and fallout radionuclide tracers

29. Spatial and temporal variability of $^7$Be and $^{210}$Pb wet deposition during four successive monsoon storms in a catchment of northern Laos

30. Long-term soil carbon loss and accumulation in a catchment following the conversion of forest to arable land in northern Laos

31. Impact of slope gradient on soil surface features and infiltration on steep slopes in northern Laos

32. Land Use and Water Quality Along a Mekong Tributary in Northern Lao P.D.R

33. Conflict, migration and land-cover changes in Indochina: a hydrological assessment

34. Trapping efficiencies of cultivated and natural riparian vegetation of northern Laos

35. Interactions between root growth, slope and soil detachment depending on land use : a case study in a small mountain catchment of Northern Laos

Catalog

Searchworks

Select search scope, currently: Articles Catalog books, media & more in Jio Institute collections Articles journal articles & other e-resources

Search

Search Constraints

Refine your results

Search Limiters

Topic

Publication Year Range

Language

Publication Type

Journal

Database

Publisher

35 results on '"Oloth Sengtaheuanghoung"'

Search Results

Catalog

Select search scope, currently: Articles

Catalog

books, media & more in Jio Institute collections

Articles

journal articles & other e-resources