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The fabrication of nano reinforced metal matrix composites (MMCs) is scientifically essential to further upgrade the thermal, electrical, and mechanical properties of current MMCs. Here, we present a green molecular mixing (MLM) of silver (Ag) and graphene (G) to overcome these challenges. Experimental results show that the green MLM allows to homogeneously mix 3 vol. % of G as observed with traditional MLM while adding a control on the oxidation steps. Metal and GO reductions can be precisely control by varying the solution temperature. Highly thermal conductivity and strong elastic modulus nanocomposites are fabricated making it an eco-friendlier mixing process.

Les agriculteurs utilisant les eaux des khettaras, galeries souterraines drainant la nappe phréatique et donnant un accès collectif à l’eau souterraine dans les oasis, font aujourd’hui face à un dilemme. Les khettaras se tarissent sous l’effet conjugué du pompage pour l’eau potable et de l’irrigation des exploitations agricoles des nouvelles extensions, et d’une recharge décroissante de la nappe. Leurs khettaras menacées de disparition, certains collectifs ont choisi d’installer des puits ou des forages alimentés par l’énergie solaire. Cela permet de renforcer le débit des khettaras et ainsi de maintenir l’accès collectif à l’eau souterraine, mais ces installations contribuent aussi à sa surexploitation. Dans cet article, nous mettons en discussion ce choix cornélien des communautés oasiennes dans le sud du Maroc. Des observations de terrain, l’analyse des images satellites, et des enquêtes avec les agriculteurs ont permis de comprendre le contexte d’émergence d’un dispositif associant la khettara au pompage par énergie solaire, d’analyser sa conception technique et de mettre en évidence la capacité des oasiens à intervenir sur les règles de gestion pour superposer ce dispositif technique et institutionnel nouveau au système traditionnel des khettaras. Cet article contribue à une réflexion sur la durabilité de l’accès à l’eau souterraine dans ce contexte présaharien.

“Merjas” represent temporary wetlands in the Sebou-Delta in the northwest of Morocco. These temporary wetlands have been partially incorporated in a large-scale irrigation system, but this ecosystem still provides ecosystem services to the riparian population besides providing a habitat area for animal and plant species, contributing to flood control and other cultural ecosystem services. However, temporary wetlands and the services they provide are perceived differently by stakeholders. In particular, the opposition of viewing them as productive lands that need to be further developed through drainage and irrigation facilities or as buffer zones for flood protection generates conflicts of their use and creates an unknown future of them. Nature Based Solutions, as an emergent umbrella concept that is based on natural processes enhancing biodiversity and the provision of ecosystem services, provides an interesting lens to study the (conflicting) multiple ecosystem services in temporary wetlands.The objective of this study is to analyze the hydrological dynamics of merjas on a spatio-temporal scale using remote sensing, and how existing and future irrigation development could affect the provision of ecosystem services.Our work combines hydrological analysis using remote sensing with an analysis of ecosystem services, based on field surveys. The results of the study will be formalized in different management scenarios and then used for discussion in multi-actor workshops. Our multidisciplinary approach brings about the originality of the work in a low-informed context where access to data is difficult.The use of NBS in the case of the Gharb plain could contribute to solving the problem of flooding and conserve its socio-environmental heritage. We developed a framework consisting of 3 steps: definition of the framework, identification of the challenge and co-creation of scenarios. For our case study, we highlight the ecosystem characteristics of the environment and the importance of the participatory approach for the success of NBS. This roadmap aims to provide the actors involved with an updated reflection on the developments that could be implemented for temporary wetlands in the Sebou-Delta and to develop an approach of interest to other wetlands elsewhere to preserve natural resources and taking into consideration the effects of climate change.

The oases of the pre-Saharan basin of Wadi Ferkla in southeastern Morocco receives low and erratic rainfall (average of 141 mm/year and inter-annual standard deviation of 70 mm - Ait-Bouijane rain gauge over the period 1961-2018). From the 70's, surface and groundwater are increasingly used due to the expansion of irrigation, mainly along two wadis, namely Wadis Ferkla and Satt originating in the High-Atlas and the Anti-Atlas Mountains, respectively. Their flows reach the Ferkla’s irrigated perimeters only when the volume of the flood events exceed upstream evaporation, withdrawals and riverbed's infiltration.Nowadays, these irrigated perimeters exert significant pressure on groundwater resources, through numerous drillings equipped with pumping systems, most of them are powered by solar energy. This unsustainable situation incentivizes individual farmers to design and implement innovative technics to increase water access for their farms. For instance, the spreading of floodwaters - an ancestral and collective irrigation practice in traditional oases - is currently being adopted and adapted by individuals at the farm level. The technique consists on partially diverting flood flows into earthen basins. The stored water either infiltrates to recharge local aquifers, or is pumped for flood irrigation of date palms.An experimental protocol was set up to characterize groundwater recharge below one of these on-farm basins equipped with a recharge well. Barometric probes were installed in the basin, in the recharge well and in neighboring boreholes to automatically monitor water table levels (10-minute-time-step). Manual measurements were performed regularly to calibrate the monitoring probes. A topographic survey of the monitoring points and of the basin aimed at deriving piezometric levels from water levels measurements and estimating the height-surface-volume curves of the basin. After 7 months of continuous monitoring, 3 flood events were recorded. The establishment of the basin water balance at a fine time-resolution allowed estimating its different components including the infiltration rate influencing groundwater recharge. An Analytical modeling of this process was developed to explore alternative design and management options of the basin. This approach aims to contribute to a broader reflection on securing water management in this fragile oasis ecosystem.

International audience; Despite the attention given to the water-energy-food nexus, there is little field evidence of how this plays out for irrigators. This article analyses the diversity of irrigation system configurations and their related water and energy use in semi-arid Morocco, where groundwater-fed and pressurized drip irrigation, although supposedly thrifty, is energy intensive. The analysis relying on onhydraulic calculations and multiple linear regressions was based on interviews,observations and measurements on irrigation systems in 25 farms. The resultsshow that each farmer used between one and three pumps and up to two stor-age reservoirs to pump groundwater from up to 120 m deep borehole(s) andtransfer it along a distance often exceeding 2 km to reach available fertile landsthat are rented. Such distances had little effect on the system-wise energy con-sumption, varying between 4.62 and 4.88 kWh m3, although the recycled carengines powering these irrigation systems were largely inefficient, consumingon average 2.5 kWh m3. State subsidies encourage these water-intensive andenergy-inefficient farming systems, increasing pressure on groundwater andland. These findings underline the importance of going beyond a strict nexusperspective, as expansion of the‘groundwater economy’is accompanied byconflicts over tenure and increasing inequalities in access to water thatthreaten the sustainability of irrigated agriculture.

Coastal agricultural systems in Southeast Asia are vulnerable to climate change. The combination of rising sea levels and extreme rainfall events is eroding fragile coastlines that protect emblematic “rice bowls” across the region. A series of recent damaging floods in Southeastern Thailand has raised concerns about their increased frequency. Local and regional trends in rainfall variables relevant to farming were investigated using the resampling-based Mann–Kendall test applied to four rainfall stations of the Songkhla lagoon basin during the period 1957–2019. Using the findings from long-term and multi-scale agrarian change surveys based on Mazoyer and Roudard's methodology, a vulnerability framework was used to assess the sensitivity and response capacity to these trends of the great Songkhla spit agroecosystem. Significant positive trends in the rainfall depth, number of rainy days, and maximum daily rainfall were observed in January at individual stations and across the region, especially since the early 1980s. Moreover, the annual frequency of extreme rainfall events consistently increased over the same period. The impacts on the unstable coastal main sandbar that protects the flood plain are discussed, while the effects on rice production are analyzed. The coping responses of the cultural rice and sugar palm-based agroforestry system, and the lack of adaptation of recent land-use changes are examined. The agro-ecological, economic, and social importance of the dense hedges of sugar palms to mitigate climatic risks and maintain the resilience of local livelihood systems is underlined. Propositions for short and longer-term measures to adapt water management, diversify cropping systems, and foster participatory disaster risk management are made.

The Outer Tracker of the Compact Muon Solenoid (CMS), one of the large experiments at the CERN Large Hadron Collider, will consist of about 13,200 modules, each built up of two silicon sensors. The modules and support structures include thousands of parts that contribute to positioning and cooling the sensors during operation at −30 °C. These parts should be low mass while featuring high thermal conductivity, stiffness and strength. Their thermal expansion coefficient should match that of silicon to avoid deformations during cooling cycles. Due to their unique thermal and mechanical properties, aluminium-carbon fibre (Al/Cf) Metal Matrix Composites are the material of choice to produce such light and stable thermal management components for High Energy Physics detectors. For the CMS Outer Tracker, about 500,000 cm3 of Al/Cf raw material will be required to be produced through a reliable process to guarantee consistent properties throughout parts manufacturing. Two Al/Cf production routes are currently considered: liquid casting by gas-pressure infiltration and a powder metallurgy process based on continuous semi-liquid phase sintering. The dimensional stability of the resulting material is of paramount importance. Irreversible change of shape may be induced by moisture adsorption and the onset of galvanic corrosion at the discontinuous interfaces between Cf and Al. This paper presents the results of an extensive investigation through Computed Microtomography, direct microscopical investigations, analysis of the interfaces and metrology measurements aimed at comparing and interpreting the response to different environments of the respective products. The results obtained confirm the suitability of the two investigated Al/Cf MMCs for application to components of the CMS Outer Tracker, requiring tight geometrical control and microstructural stability over time. However, for PM parts sintered through the semi-liquid phase process, a multilayered protective noble metal coating is necessary the make them impervious to moisture, allowing dimensional stability to be guaranteed and the onset of corrosion phenomena to be avoided, while the product obtained by gas-pressure infiltration has shown less sensitive even to extreme temperature-humidity cycles and may be used uncoated.

Purpose: This study aimed to define the behavioral determinants influencing the decision of intensivists to consult a poison center (PC) when managing patients with calcium channel blocker (CCB) poisoning. Material and methods: Semi-structured interviews were conducted involving a convenience sample of 18 intensivists. Two independent reviewers analyzed the interview responses using the Theoretical Domains Framework. Based on the impact and frequency of the reported behaviors, we selected the most relevant domains likely to influence intensivists’ decision to consult a PC for CCB poisoning. Results: Beliefs influencing physicians positively to consult a PC for CCB poisoning were identified in the following domains: knowledge (e.g., lower level of evidence), social or professional role and identity (e.g., high credibility attributed to the PC), reinforcement (e.g., multiple drug poisoning, infrequent or potentially lethal poisoning, medicolegal considerations), and behavioral regulation (e.g., facilitated access of PC to patient’s hospital chart, direct communication with a toxicologist). Beliefs deterring physicians from consulting a PC for CCB poisoning were identified in the following domains: knowledge (e.g., better awareness of recommendations decreases tendency to call), goals (e.g., priority for patient stabilization), and memory, attention, and decision process (e.g., cognitive overload due to an unstable patient). Conclusion: This qualitative study identified potential behavioral targets that future implementation strategies should address to improve collaboration between PCs and intensivists. In light of our results, the Québec PC now asks clinicians if the poisoned patient is unstable prior to collecting any other information. When necessary, a teleconference with the toxicologist is proposed earlier than before.

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.

Hydropower production is altering the Mekong River basin’s riverine ecosystems, which contain the world’s largest inland fishery and provide food security and livelihoods to millions of people. The basin’s hydropower reservoir storage, which may rise from ∼2% of its mean annual flow in 2008 to ∼20% in 2025, is attenuating seasonal flow variability downstream of many dams with integral powerhouses and large storage reservoirs. In addition, tributary diversions for off-stream energy production are reducing downstream flows and augmenting them in recipient tributaries. To help manage tradeoffs between dam benefits (hydropower, irrigation, flood control, domestic water supply, and navigation) and their consequences for livelihoods and ecosystems, we review observed and projected impacts on river flows along both the Mekong mainstream and its tributaries. We include the effects of diversions and inter-basin transfers, which prior reviews of flow alteration in the Mekong basin have largely neglected. We also discuss the extent to which concurrent changes in climate, water demand, and land use, may offset or exacerbate hydropower-induced flow alteration. Our major recommendations for assessing hydrological impacts in the Mekong and other basins undergoing rapid hydropower development include synchronizing and integrating observational and modeling studies, improving the accuracy of reservoir water balances, evaluating multi-objective reservoir operating rules, examining hydropeaking-induced flow alteration, conducting multi-dam safety assessments, evaluating flow indicators relevant to local ecosystems and livelihoods, and considering alternative energy sources and reservoir sedimentation in long-term projections. Finally, we strongly recommend that dam impact studies consider hydrological alteration in conjunction with fish passage barriers, geomorphic changes and other contemporaneous stressors.

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.

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.

In PNAS, Fan et al. (1) propose that landscape-scale hydrologic convergence along topography is the main driver of rooting depth. Fan et al. (1) base their assessment on a compilation of published reports and the development of an inverse modeling applied at the global scale. One of the central hypotheses of Fan et al. (1) is that the water table depth (WTD) both determines—as a readily available water supply—and restricts—due to lack of oxygen below the water table—rooting depth, as indicated by the alignment of points with 1:1 line in their figure 3 F . However, some points in their figure … [↵][1]1To whom correspondence should be addressed. Email: alain.pierret{at}ird.fr. [1]: #xref-corresp-1-1

Groundwater resources are vital for the well-being and livelihoods of most of the ten million people living in the Dry Zone of central Myanmar. Despite this importance, there is remarkably little known or documented on the nature, extent and use of these resources. This contribution has attempted to address this gap by reviewing the literature, gathering data and stakeholder consultations. The study reveals that utilizable groundwater is present across most of the Dry Zone, most notably in the unconsolidated sedimentary aquifers that are present across large portions of the region. However, rates of replenishment appear to be relatively modest, and use is limited by high levels of salinity and arsenic that are naturally present in some areas. The scope to access groundwater is generally good, and development has steadily increased to provide water supply for domestic, agriculture and industry. In broad terms, is would appear that prospects to expand groundwater use for irrigation and other purposes are good in almost all districts. In more hydrogeologically complex settings in particular, a lack of information creates more risk that may add to drilling costs. More detailed assessments and databases are required to support effective resource management.

This study focuses on Laos, a landlocked nation located in South-East Asia with sub-tropical climate and highly seasonal rainfall distribution. Laos is one of the world’s least developed countries, and currently witnesses an unprecedented level of development that is highly reliant on its natural resources, including groundwater. There is currently very limited data and no nationwide assessment of shallow (

Groundwater recharge remains almost totally unknown across the Mekong River Basin, hindering the evaluation of groundwater potential for irrigation. A regional regression model was developed to map groundwater recharge across the Lower Mekong Basin where agricultural water demand is increasing, especially during the dry season. The model was calibrated with baseflow computed with the local-minimum flow separation method applied to streamflow recorded in 65 unregulated sub-catchments since 1951. Our results, in agreement with previous local studies, indicate that spatial variations in groundwater recharge are predominantly controlled by the climate (rainfall and evapotranspiration) while aquifer characteristics seem to play a secondary role at this regional scale. While this analysis suggests large scope for expanding agricultural groundwater use, the map derived from this study provides a simple way to assess the limits of groundwater-fed irrigation development. Further data measurements to capture local variations in hydrogeology will be required to refine the evaluation of recharge rates to support practical implementations.

Melioidosis, a severe infection with the environmental bacterium Burkholderia pseudomallei, is being recognised increasingly frequently. What determines its uneven distribution within endemic areas is poorly understood. We cultured soil from a rice field in Laos for B. pseudomallei at different depths on 4 occasions over a 13-month period. We also measured physical and chemical parameters in order to identify associated characteristics. Overall, 195 of 653 samples (29.7%) yielded B. pseudomallei. A higher prevalence of B. pseudomallei was found at soil depths greater than the 30 cm currently recommended for B. pseudomallei environmental sampling. B. pseudomallei was associated with a high soil water content and low total nitrogen, carbon and organic matter content. Our results suggested that a sampling grid of 25 five metre square quadrats (i.e. 25 × 25 m) should be sufficient to detect B. pseudomallei at a given location if samples are taken at a soil depth of at least 60 cm. However, culture of B. pseudomallei in environmental samples is difficult and liable to variation. Future studies should both rely on molecular approaches and address the micro-heterogeneity of soil when investigating physico-chemical associations with the presence of B. pseudomallei.

Study region: Increasing demographic pressure and economic development in the Mekong Basin result in greater dependency on river water resources and increased vulnerability to streamflow variations. Study focus: Improved knowledge of flow variability is therefore paramount, especially in remote catchments, rarely gauged, and inhabited by vulnerable populations. We present simple multivariate power-law relationships for estimating streamflow metrics in ungauged areas, from easily obtained catchment characteristics. The relations were derived from weighted least square regression applied to streamflow, climate, soil, geographic, geomorphologic and land-cover characteristics of 65 gauged catchments in the Lower Mekong Basin. Step-wise and best subset regressions were used concurrently to maximize the prediction R-squared computed by leave-one-out cross-validations, thus ensuring parsimonious, yet accurate relationships. New hydrological insights for the region : A combination of 3–6 explanatory variables – chosen among annual rainfall, drainage area, perimeter, elevation, slope, drainage density and latitude – is sufficient to predict a range of flow metrics with a prediction R-squared ranging from 84 to 95%. The inclusion of forest or paddy percentage coverage as an additional explanatory variable led to slight improvements in the predictive power of some of the low-flow models (lowest prediction R-squared = 89%). A physical interpretation of the model structure was possible for most of the resulting relationships. Compared to regional regression models developed in other parts of the world, this new set of equations performs reasonably well.

While there is increasing evidence concerning the detrimental effects of expanding rubber plantations on biodiversity and local water balances, their implications on regional hydrology remain uncertain. We studied a mesoscale watershed (100 km2) in the Xishuangbanna prefecture, Yunnan Province, China. The influence of land-cover change on streamflow recorded since 1992 was isolated from that of rainfall variability using cross-simulation matrices produced with the monthly lumped conceptual water balance model GR2M. Our results indicate a statistically significant reduction in wet and dry season streamflow from 1992 to 2002, followed by an insignificant increase until 2006. Analysis of satellite images from 1992, 2002, 2007, and 2010 shows a gradual increase in the areal percentage of rubber tree plantations at the watershed scale. However, there were marked heterogeneities in land conversions (between forest, farmland, grassland, and rubber tree plantations), and in their distribution across elevations and slopes, among the studied periods. Possible effects of this heterogeneity on hydrological processes, controlled mainly by infiltration and evapotranspiration, are discussed in light of the hydrological changes observed over the study period. We suggest pathways to improve the eco-hydrological functionalities of rubber tree plantations, particularly those enhancing dry-season base flow, and recommend how to monitor them.

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.

Trends in rainfall series were investigated at 16 stations in Ghana over the period 1960–2005. Time series were first de-correlated using an effective pre-whitening methodology and then submitted to the resampling-based Mann-Kendall test. Field significances were assessed using the regional average Kendall statistic. Although no significant changes were observed in annual rainfall, the analysis reveals: (a) a reduction in the number of wet season days totalling less than 20 mm of rainfall, between latitudes 6° and 9.5°N; (b) a delay (about 0.5 d year‐1) in the wet season onset at several locations throughout the country; and (c) a lengthening (about 0.1 d year‐1) of rainless periods during the wet season in the south and centre of Ghana. All these changes, which remained insignificant at more than half of the individual stations, were found to be regionally significant at the 95% confidence level. The results highlight the importance of evaluating regional significance when investigating climate ...

Regional and local trends in rainfall intensity, frequency, seasonality, and extremes were analyzed in the central Mekong Basin in continental Southeast Asia over the period 1953–2004 using the modified Mann–Kendall test, accounting for long-term persistence and the regional average of the Kendall's statistic. Regionally significant and insignificant wetting tendencies of the dry and wet seasons, respectively, were found to be consistent with rainfall alterations in the neighboring southeastern part of China and attributed by previous studies to the weakening of the East Asia Summer and Winter Monsoons. These observations suggest the existence of causal links between global warming and rainfall changes observed in continental Southeast Asia. Although these changes most likely did not alter agricultural production, they confirm the need to account for climate change impacts when assessing water resources availability in this region under rapid economic development.

Comme dans la plupart des régions, les zones arides ont bénéficié de plusieurs vagues d'aménagements hydroagricoles durant la seconde moitié du XX e siècle pour ralentir, stocker et rendre accessibles des écoulements sporadiques et violents peu utilisables par des ouvrages au fil de l'eau. Cette succession d'aménagements superposés est souvent mal valorisée comme le montrent divers bilans réalisés dans des bassins du Centre tunisien et du Nord Mexique où les retenues collinaires favorisent, avant tout, les pertes évaporatoires. Sur la base de ces constats, les gouvernements ont cherché à améliorer la gestion technique des ouvrages en favorisant les transferts d'eau vers les réservoirs souterrains et cherchent à mobiliser les ressources en eau non conventionnelles avec quelques succès, mais seulement dans des situations spécifiques en raison de leurs coûts élevés (désalinisation), d'une difficile acceptation (réutilisation des eaux usées) ou de leur volume peu important (eau atmosphérique). Toutes ces initiatives n'ont pas arrêté la surexploitation des nappes phréatiques, et peu à peu se mettent en place plusieurs initiatives pour diminuer la demande en eau tout en augmentant la production alimentaire. Cette nouvelle politique finance l'installation des techniques d'irrigation économes (aspersion, goutte-à-goutte, polymères gonflants, conduites verticales, etc.) pour remplacer l'irrigation gravitaire majoritairement utilisée. Après quelques années, il faut bien reconnaître que l'impact de ces nouvelles techniques est moins important que prévu soit à cause d'une utilisation inadéquate, soit par le fait de nouveaux comportements qu'elles ont suscités. Actuellement, les pouvoirs publics testent des outils complémentaires économiques et réglementaires pour rendre plus efficaces ces changements techniques.

Summary The Merguellil catchment (1183 km2), whose runoff is a major water resource for the Kairouan area in semi-arid Tunisia, was equipped with water and soil conservation works (WSCW) during the 1990s, mainly to reduce soil erosion and silting of the downstream El Haouareb dam. The spatial configuration of the hydro-meteorological station network makes it possible to characterize the catchment-scale hydrological impact of the WSCW. The catchment is subdivided into two parts, the upper subcatchment and the lower subarea. The latter covers 84% of the catchment surface area and gathers 97% of the surfaces controlled by WSCW. The space–time variability of the rainfall–runoff relationship is first analysed, comparing the runoff responses from the two nested catchments for different rain event depth ranges. A non-parametric test, based on a resampling approach, is applied to the lower subarea runoff simulated with the GR4J daily lumped rainfall–runoff model, which is calibrated for several subsets of data. Results indicate that from 1989 to 2005, the runoff produced by rainfall below 40 mm in the lower subarea was reduced by some 71–75%, a significant change at the 95% confidence level. This drop in runoff is estimated at 41–50% when considering all rain depths and at 28–32% when including the upper subcatchment in the analysis. No runoff change is found for above-40 mm rains in the lower subarea, nor for any rain depth range in the upper subcatchment. An analysis of various possible sources for the runoff reduction such as climate, land use/land cover, or water exchanges with the aquifer, led to the conclusion that WSCW, which were developed over 32% of the lower subarea since 1989, are the most likely cause for that reduction. Their sharp hydrological effects should be taken into account in order to manage the water resources at the river basin scale, especially in populated semi-arid areas where conflicts between water uses increase dramatically.

A shortcut review was carried out to establish whether silibinin is better than conservative management at reducing liver transplantation and death after poisoning with amatoxin-containing mushrooms. Thirty-eight papers were found in Medline and 86 in EMBASE using the reported searches. Of these, five presented the best evidence to answer the clinical question. The author, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses of these best papers are tabulated. It is concluded that the evidence is limited, but given the lack of alternative treatments in patients with suspected amatoxin-containing mushroom poisoning and the relatively few adverse effects, silibinin should be considered in some patients.

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.

As hydropower dam construction in rapidly growing economies dislodges communities, rural development experts must help the displaced make their livelihoods in new lacustrine environments. One question is whether the dam infrastructure can directly benefit those who remain within the vicinity of the reservoir. Integrated water resource management seeks to concurrently consider hydrological, socioeconomic, and ecological factors, yet water managers lack the information needed to include livelihoods in their analyses. The objective of this paper is to develop tools and plans for coordinating hydropower reservoir operation and management for rural livelihoods. Specifically, this study investigates how dam management may accommodate vegetable farming on the banks of a reservoir. The intervention investigated is to lower water levels during the cultivation period in order to expose shoreline gardens. Based on the recession agriculture rule, evaluated through simulation of a dam in Lao People's Democratic Republic, the average annual hydropower production was reduced by between 0.4 and 8.1%, depending on the agricultural goal, with the loss to power occurring mainly in the months April to June. By focusing on hydropower reservoir systems, the techniques developed in this study have the potential to be applied to support communities throughout the world that farm on the shorelines of water reservoirs.

Climate vagaries and the lack of irrigation, frequently combined with coarse-textured sandy and unevenly distributed saline soils, explain low crop yields and the endemic relative poverty of the rural population in Northeast Thailand (NET). Local and regional trends in agriculturally-relevant rainfall variables were investigated using the Mann-Kendall test, modified to account for serial correlation, and applied to 17 stations across NET, and the regional average Kendall's statistic. Limited changes in rainfall frequency, intensity and seasonality are observed at individual stations over the study period (1953–2004). But we found a significant regional trend toward a wetter dry season. Based on an intimate knowledge of the local farming systems, we discuss the cropping systems adaptation to these rainfall changes. If the wetting of the dry season extends in the future, as expected according to most climate projections, households would not find it difficult to adapt, except for the problems caused by temperature rise, mainly due to their renowned adaptive capacity and high mobility that historically produced diverse and resilient rural livelihood systems.

International audience; Fully dense carbon fiber-reinforced copper and aluminum matrix (Cu-CF and Al-CF) composites were fabricated by hot press without the need for an interfacial chemical compound. With 30 vol% carbon fiber, the thermal expansion coefficients (TECs) of pure Cu and Al were decreased to 13.5 × 10−6 and 15.5 × 10−6/K, respectively. These improved TECs of Cu-CF and Al-CF composites were maintained after 16 thermal cycles; moreover, the TEC of the 30 vol% Cu-CF composite was stable after 2500 thermal cycles between −40 and 150 °C. The thermal strain caused by the TEC mismatch between the matrix and the carbon fiber enables mechanical enhancement at the matrix/carbon fiber interface and allows conservation of the improved TECs of Cu-CF and Al-CF composites after thermal cycles.

Hydropower and irrigation developments to address rising demand for food and energy are modifying the water balance of the Mekong Basin. Infrastructure investment decisions are also frequently made from a sub-catchment perspective. This paper compares river flows with irrigation development stages in the Nam Ngum sub-basin where the potential for irrigation and hydropower expansion is largely untapped. It shows that full hydropower development in this basin allows irrigation water use to triple, even as it reduces competition with environmental flow requirements. The implications for the wider Mekong are, however, unclear, particularly given uncertainty over parallel transformations elsewhere in the basin.

Though there are surprisingly few estimates of the economic benefits of coordinated infrastructure development and operations in international river basins, there is a widespread belief that improved cooperation is beneficial for managing water scarcity and variability. Hydro-economic optimization models are commonly-used for identifying efficient allocation of water across time and space, but such models typically assume full coordination. In the real world, investment and operational decisions for specific projects are often made without full consideration of potential downstream impacts. This paper describes a tractable methodology for evaluating the economic benefits of infrastructure coordination. We demonstrate its application over a range of water availability scenarios in a catchment of the Mekong located in Lao PDR, the Nam Ngum River Basin. Results from this basin suggest that coordination improves system net benefits from irrigation and hydropower by approximately 3–12% (or US$12-53 million/yr) assuming moderate levels of flood control, and that the magnitude of coordination benefits generally increases with the level of water availability and with inflow variability. Similar analyses would be useful for developing a systematic understanding of the factors that increase the costs of non-cooperation in river basin systems worldwide, and would likely help to improve targeting of efforts to stimulate complicated negotiations over water resources.

International audience; We investigated the impact of land-use change on the hydrology of different major Lao tributary watersheds of Mekong River. The region is the North of Laos centred on Luang Prabang and the watersheds are the Nam Khan, Nam Ou, Nam Suong, Nam Lik and Nam Ngum. An additional small agricultural catchment called Houay Pano close to the Nam Khan, is also considered. We used the lumped rainfall–-runoff conceptual models GR4J and GR2M, developed by Irstea in France, the Mekong River Commission hydro-meteorological database and the Japanese Aphrodite meteorological database. The objective was to detect in the hydrological regime of the watersheds an impact of de(re)forestation, processes known to have occurred since the 1980s, but at a degree which has not been quantified. For this purpose we adopted the cross simulation methodology developed by Irstea which has proved to be efficient to detect trends in long term watershed hydrology. The results did not show any significant hydrological change since 1960. On the other hand the application of the same methodology to the small catchment Houay Pano surveyed since 2001 proved to be convincing. We saw evidence of the impact of slash and burn practice, followed by a long fallow period, on a catchment's hydrology over a seven year period.

The Vietnam War played a decisive role in the pre‐1990s deforestation of the lower Mekong Basin, which in turn likely influenced regional broad‐scale hydrology. This note presents and discusses new analyses that strengthen this thesis. Although concurrent overestimation of discharge and underestimation of rainfall, a couple of years after bombing climaxed in the early 1970s, could theoretically explain the sharp rise in water yield previously attributed to bomb‐induced deforestation, new observations suggest that bombing has durably modified the landscape: by 2002, degraded forests still largely overlapped with areas heavily bombed 30 years earlier. This corroborates observed long‐term hydrological changes and suggests that warfare‐induced deforestation has more profound and durable hydrological effects than previously thought.

International audience; The subject of change detection in climate time series has recently received greater interest as the perception of a human-induced change in the climate is now widely accepted. However, changes in regional precipitation and temperature remain uncertain. This study characterizes projected fine-scale changes in precipitation and temperature in continental Southeast Asia over the period 1960-2049. Twenty four annual variables were derived from grid-based daily precipitation and temperature produced by the PRECIS regional climate model under A2 and B2 scenarios. These time series, capturing precipitation intensities (classified as low, medium and high), seasonality and extremes in precipitation and temperature, were subjected to the modified Mann-Kendall trend detection test accounting for long-term persistence. The results indicate that temperature increases over the whole region with steeper trends in higher latitudes. Increases in annual precipitation, mainly restricted to Myanmar and the Gulf of Thailand, result from increases in high precipitation during the wet season. Decreases are observed mainly over the sea and caused by a reduction of low precipitation. Changes in the occurrence of the monsoon affect the low-latitude sea areas only. By showing that significant precipitation change are minor over land areas, these results challenge most of the previous studies that suggested significant precipitation changes over Southeast Asia, often mixing up multi-decadal variability and long-term unidirectional trends. Significant changes in precipitation and temperature may induce higher agricultural yields as steepest temperature and precipitation increases will predominantly affect the coldest and driest land areas of the region.