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International audience; Groundwater is essential for early-season agriculture in many arid regions. In such regions, however, groundwater recharge is generally low, leading to groundwater degradation. State responses are seldom effective in addressing this issue, which leads to fatalist narratives of the unsustainability of profitable agricultural growth and the collapse of aquifers. We argue that such narratives make it difficult to recognise more promising instances in which communities find solutions to groundwater degradation. We call for a fine-grained analysis of the social practices around the use of groundwater, which, we argue, represent a process of commoning. We do so while recognising that the collective action of communities is embedded in an intricate set of relations with other stakeholders including the state, and that the positive environmental and transformative social change that is often associated with commoning cannot be taken for granted at the outset. Building on the case of the arid Drâa Valley in Morocco where watermelon production has expanded rapidly, we illustrate how the process of commoning evolves through different social practices, including: 1) the use of new farming practices that reveal the potential of the aquifer; 2) the representation of the aquifer as severely degraded and the development of a narrative around it being a collective good to be protected against outsiders; 3) the defining and negotiating of rules to control groundwater access and use; and 4) the engagement in negotiations and the resolving of conflicts. Our analysis shows that commoning, as performed by young local farmers, is about extending the lifespan of the aquifer for agricultural production rather than preserving it indefinitely; however, an examination of commoning practices also reveals the capacity of the community to change the course of the future.

International audience; This article provides a theoretical introduction to the Special Issue and briefly presents the various contributions. It starts with a general plea for inserting the analysis of groundwater and its gradual depletion into a broader critical analysis of 'development'; it does so in order to trace how particular forms of groundwater use and management are intrinsic to distinct-gendered and racialised-processes of differentiation and exploitation such as settler colonialism and capitalism. We go on to argue, however, that too much insistence on explaining empirical realities in terms of such structural processes has its limitations. It risks strengthening their overwhelming power and reconfirming the oppression and marginalisation that they create. We therefore suggest that methodological and ethnographic attention to practices may help identify less predictable and sometimes surprising trajectories of change. Our foregrounding of practices implies treating terms such as transformation and sustainability as fluid, the discussion of which needs to be anchored in the situated and always-specific practical work of using, accessing, caring for, sharing and knowing groundwater. Theoretical insights about how the world is patterned or structured then serve not as the framework in which to insert empirical findings, but as entry points for further analysis, reflection and conversation, fuelling forms of experimentation and joint learning about how to think and do transformations to groundwater sustainability.

International audience; In many countries, the challenge of sustaining rural water supplies is entrusted to community organizations, which have difficulties in performing durably the operation, maintenance and cost recovery of rural water supply systems. This paper analyzes how rural communities struggle to ensure a sustainable access to water, while seeking close interaction with outside actors such as the State, NGOs, and politicians. The analysis is based on field observations, interviews and participatory workshops in four community-managed water supply systems in Brazil and Tunisia. To sustain the access to water, communities limit their dependance on community-managed water supply systems and diversify water sources for different uses; they adapt the technical and organizational dimensions of water supply systems through bricolage ; and use political leverage to obtain financial and technical support. Understanding how communities adapt the infrastructure and the organization of rural water supply, in close interaction with external actors, may inspire water providers in designing more resilient water systems.; Dans de nombreux pays, l’approvisionnement en eau en milieu rural est confié aux organisations communautaires, qui éprouvent des difficultés à en assurer durablement l’exploitation, la maintenance et le recouvrement des coûts. Cet article analyse comment les communautés rurales luttent pour assurer un accès durable à l’eau, en sollicitant l’État, des ONG et des élus. L’analyse est basée sur des observations de terrain, des entretiens et des ateliers participatifs dans quatre communautés dans un contexte d’extrême rareté de l’eau au Brésil et en Tunisie. Pour maintenir un accès durable à l’eau, les communautés limitent leur dépendance à l’égard des systèmes collectifs et diversifient les sources d’eau pour différents usages ; elles adaptent l’infrastructure et l’organisation des systèmes collectifs par le bricolage ; et elles utilisent l’influence politique pour obtenir des soutiens des acteurs externes. Comprendre comment les communautés adaptent l’infrastructure et l’organisation de l’accès à l’eau, en étroite interaction avec les acteurs externes, peuvent inspirer les fournisseurs d’eau dans la conception de systèmes d’approvisionnement en eau plus résilients.

The current focus on water saving in drip irrigation projects has stifled more classical engineering debates on the relevance of different irrigation techniques for specific field conditions. We show that these debates remain important by analysing a drip irrigation project implemented in a sprinkler irrigation district in north-west Morocco. The objective is to understand the apparent paradox of a state-promoted switch to drip irrigation, provided free of charge to farmers who welcomed the project but continued using sprinkler irrigation. Data were gathered during field observations and in interviews with 138 farmers, while secondary data came from the irrigation authority. The results show that most farmers were interested in the drip irrigation project, which solved existing problems of the sprinkler network, including the difficulty of sharing hydrants, high water bills and sharing mobile sprinkler equipment. However, once the project had provided individual water access and customized water bills, 48% of farmers switched totally or partially back to sprinkler irrigation, which they considered better suited to field conditions (soils, crops, irrigation frequency). The implementation of drip irrigation in large-scale irrigation schemes needs to go beyond the objective of water saving and be adapted to specific natural and socio-economic conditions.

International audience; This study presents a decision support tool that evaluates the environmental efficiency of reusing treated wastewater for agricultural irrigation, among other options. The developed tool is published as open source at https://doi.org/10.18167/DVN1/YLP1BA. The objective of this decision support tool is to facilitate the interpretation of the Life Cycle Assessment (LCA) results by progressively reducing the non-discriminatory impacts to solve the difficulty of making a decision with a large number of criteria. This framework was applied to a representative case of reuse of reclaimed water for vine irrigation at the Murviel-Les-Montpellier experimental site (Hérault, France). It was then generalized through modeling assumptions to consider different reuse scenarios. To highlight situations in which the supply of recycled water for irrigation may or may not provide significant environmental benefits, four main parameters were varied: (i) tertiary treatment technologies, (ii) availability of conventional water sources, (iii) energy mix composition. The results show that the environmental impact of treated wastewater reuse depends directly on the type of tertiary treatment technology and the location of the treatment plant in relation to the field and other water sources. The decision support tool has identified where wastewater reuse is clearly an environmentally beneficial source of irrigation among surface and groundwater sources (e.g., WWTP closer to field than river, groundwater too deep, tertiary treatment environmentally beneficial). However, there are many situations where the decision support process cannot distinguish between reuse of treated wastewater for agricultural irrigation and conventional water sources, especially when the nutrient content of treated municipal wastewater is insufficient to offset the negative effects of high energy requirements and chemicals of tertiary treatment.

International audience; In a climate change context, changing temperature and precipitation patterns are expected to have strong impacts on Brazilian eucalypt plantations. Implementing adaptive water-efficient management practices is thus becoming necessary to maintain high levels of productivity while preserving the water resources. This paper investigates the ability of eucalypt farmers to modify their current silvicultural practices in order to adapt to drought in the near future. We ran a choice experiment in the state of Minas Gerais, among 80 eucalypt tree farmers, who were asked to choose from several management options associated with various financial supports. The results show that adaptation by reducing the length of the eucalypt rotation proves to be by far the preferred option, despite the associated costs. On the contrary, reducing density appears to be the least chosen option by the respondents, which may suggest that they underestimate the benefits of this strategy. We moreover find a clear and relevant segmentation of farmers' choice behavior, the general preference for reducing the length of the eucalypt rotation being driven by the most vulnerable farmers of the sample

Fulfilling both “Water and soil conservation” and “Integrated rural development” objectives, hillside reservoirs are very popular components of water and/or rural management strategies. In Central Tunisia, more than 800 reservoirs have been built since the 1950s. These have been the subject of an abundant literature by both social and physical scientists. However, this literature, which is highly segmented and often centred on the technical and economic assessment of development programs, does not help understand the different logics at work in the appropriation of these technical objects by the different actors involved. To achieve this goal, our research based on a "sociohydrological negotiation", articulates the methods and research questions of hydrology and anthropology on a same case study in Central Tunisia. An initial survey of water use and management practices around hillside reservoirs in the Merguellil Catchment revealed the wide variety of the infrastructures and the multiple functions they fulfil. These initial observations underpinned the process of negotiating an interdisciplinary framework to analyze the social, physical and technical dimensions of hillside reservoirs. To trace the history of watershed development policies implemented in the Merguellil Catchment, we first examined the multiple embedded logics underlying Tunisian hillside reservoir planning. This led to the production of “sociohydrological narratives” for four hillside reservoirs that both combined and enabled us to analyze the inhabitants’ own accounts of their reservoir history. This ethnographical material was then examined through the lense of a “resource making process”. Considering the way in which hydraulic objects function in a landscape that is both socio-political and hydrological enabled us to analyze the different aspects of this resource making process, from water valuation to the production of “hydraulic localities”.

International audience; Background and aims: Agroforestry systems combining trees with crops or pastures have been widely used to reduce water, soil, and nutrient losses and associated water pollution from agricultural lands in both temperate and tropical regions. However, reviews on improvement/efficiency and the scope of such reductions by soil, management, climate, and hydrological processes are limited.Methods: This paper synthesized the available evidence on the reduction in surface runoff, soil erosion, nutrient, and pollutant losses (e.g., herbicides, pesticides, and antibiotics) to quantify the effectiveness of agroforestry systems on water quality improvement based on published studies.Results: On average, agroforestry systems reduced surface runoff, soil, organic carbon, and related nutrient losses by 1–100%, 0–97%, –175–92%, and –265–100%, respectively, with average values of 58%, 65%, 9%, and 50%, respectively. They also lowered herbicide, pesticide, and other pollutant losses by –55–100% (49% on average).Conclusions: Reduction efficiency of agroforestry systems is site-dependent and varies widely depending on different biophysical factors. A comprehensive science-based review is needed to generalize agroforestry design and site adaptability for water and soil conservation where climatic, geographical, ecological, and socio-economic conditions are relatively similar in the world.

La qualité de la datte du Majhoul renseigne beaucoup sur la bonne conduite culturale du palmier dattier. Afin d'évaluer l'effet du régime hydrique sur la qualité et la quantité des dattes au stade tamer, un essai expérimental a été conduit pendant deux années consécutives (Mars 2012-Février 2014). Sept régimes hydriques localisés ont été appliqués: régime agriculteur (T0), 100 % (T1); 80% (T2); 60 % (T3) ; 80-100-60 % (T4); 150 % (T5) et 60-100-80 % (T6) ETM. Les mesures ont porté sur la mensuration du poids frais et sec des fruits, leur teneur en eau, le rendement total et le calibrage des dattes conformément aux normes générales pour la commercialisation de la datte marocaine. Les résultats ont montré que le régime hydrique 60-100-80 % ETM a amélioré qualitativement et quantitativement le rendement des dattes. Tandis que le déficit hydrique contrôlé au seuil de 40 % a un effet significatif sur la productivité des palmiers en augmentant la catégorie I au détriment de la catégorie Extra.

International audience; Echinochloa stagnina (Retz) P. Beauv., a widespread semi-aquatic perennial grass, is a key species for the sustainability of many African wetlands. In an effort to assess interactions between hydrological regimes and management strategies targeting conservation, this study focuses on characterizing the growth of a typical East African wet grassland and describing the relative influence of floods and management practices on its growth rates. Naturally flooded grassland, subjected to a factorial design protocol with different levels of irrigation and cutting frequencies, was sampled during 15 months in the Tana River Delta, Kenya. Statistical analyses of the data, using linear mixed models accounting for temporal auto-correlation, were undertaken. Reduced cutting frequencies slightly increased growth rates, except under water-limited conditions. Increased water supply had a positive effect on growth rates, the latter noting a five- and ten-fold increase from water-limited to water non-limited to flooded conditions. Floods impacted grasslands by increasing growth rates, which attained very high values of 225 kgDM ha−1 day−1, extending growth period and limiting the negative effect of severe phytomass removal through clipping. These results support the view that rangeland and water management for the Tana River Delta, and more widely for tropical floodplain grasslands, should be jointly undertaken.

To improve the irrigation water management in oasian context, evapotranspiration assessment is required. In Tunisian oases, date palm (Phoenix dactylifera L.) is the main crop and its water use is an essential evapotranspiration element. In this research, sap flow measurement was implemented to assess the date palm transpiration inside an irrigated-drained field within which the shallow-groundwater level and the water balance elements were continuously monitored. The site is a Tunisian Saharan oasis, stamped by waterlogging and salinity manifestation and by low-frequency and irregular flooding irrigation. The cropping system is two-storey palm/grass layered system. This paper focuses on one-year period sap flow measurements using a recalibrated Granier's TDP-method. Results showed that the instantly transpiration varied with the air temperature and was high related to the shallow water table nycthemeral fluctuation. The daily transpiration ranged between 0.5 and 3.5 mm d-1 with a clear seasonal variation. A water stress appearance according to water delivery frequency during the summer season was also revealed. The one-year-cumulated date palm transpiration was about 730 mm and represented almost 60% of the overall oasis deduced evapotranspiration. From this experiment case, it was noted that the date palm tree transpiration reflect a modest water consumption (35 to 45%) relatively to the surrounding high evaporative demand and it can be deduced that date palm tree, in itself, isn't a great water consumer in such cropping conditions. After more validation, these elucidations should be considered to rethink the date palm irrigation scheduling and the water management practices inside oasis schemes.

The diversification of cropping systems encompasses different strategies that may help maintain or enhance the sustainability of agriculture. Thousands of experiments have been carried out around the world since almost five decades to evaluate and compare the performances of various diversification strategies in a wide array of agroecosystems and climates. Although these analyses have been synthesized in a growing number of meta-analyses, the information remains somewhat fragmented. A multicriteria systematic synthesis of worldwide agricultural diversification is still lacking. Here, we review all meta-analyses conducted on crop diversification strategies and produce a detailed overview of their results and of their quality. We identified and analyzed 99 meta-analyses summarizing the results of more than 3700 agronomic experiments on seven crop diversification strategies. Among these strategies, rotation and associated plant species are dominant in the literature followed by intercropping, agroforestry and landscape heterogeneity. Our analysis reveals that rotation and intercropping are associated with yield increases. Agroforestry systematically induces an improvement of biodiversity and soil quality—in particular soil organic carbon. We show that, regardless of the context, a combination of several diversification strategies outperforms any individual strategy. Our review reveals that a significant knowledge gap remains, in particular regarding water use, farmers’ profitability, product quality and production stability. Few meta-analyses investigate the performance of landscape heterogeneity and of systems with species other than cereals and pulses. Additionally, we show that most of the meta-analyses studied cannot be considered fully transparent and reproducible. Their conclusions should therefore be interpreted with caution. Our systematic mapping provides a benchmark to guide and improve the relevance and reliability of future meta-analyses in agronomy.

Morocco has well developed irrigation facilities that range from small scale communal systems based on springs, qanats or river diversions to groundwater-based individual initiatives and large scale public schemes. Water demand policies – e.g. water pricing, shift to drip irrigation, 'aquifer contracts' and other forms of participatory management – have shown little potential in curbing overexploitation of resources in many basins. Expansion of irrigated areas and the priority given to productivity have taken their toll on the environment, favored commercial agriculture, and contributed to a net depletion of groundwater estimated at 1 billion m3/year. There is a need to better align agricultural development, water conservation, and environmental objectives. After a short historical perspective, this chapter first reviews a number of trends in the irrigation sector (modernization, development of groundwater resources, wastewater reuse and desalination), before turning to regulatory and institutional issues, including participatory management, economic tools, privatization and an examination of the Plan Maroc Vert. The threats posed by climate change, water scarcity, and environmental degradation are then discussed.

Since 2007, the world has seen a rush towards natural resources, particularly land as well as water. It resulted from a convergence of the 2007- 2008 food price crisis in a context of growing populations and changing diets, and the search for alternatives to financial investment products. Although data is scarce, recent estimates show that about 42 million hectares have been acquired (Nolte, Chamberlain and Giger, 2016). Contrary to what is often highlighted, these lands are not the most marginal, underused and unowned, but are close to other resources, especially water, as well as infrastructure (roads and transport) and services. This means the resource acquisition phenomenon is embedded in a complex matrix of resources and processes which is increasingly under pressure. That said, attention has so far mainly been sectoral, focused on land issues and neglecting this interconnectedness. However, the water implications of these land deals are starting to surface.

International audience; The issues of power and equity are gaining attention in research on ecosystem services (ESs). Stakeholders benefiting from ESs are not necessarily able or authorized to participate in ES management. Thus, we have proposed an analytical framework to identify and qualify stakeholders' roles in relation to ES flows. Building on existing frameworks in the ES literature, we aimed to unravel the different direct and indirect management contributions to ES flows and link them to ES benefits. Direct management targets the functioning of ecosystems, the flows of services, and the benefits received by society, whereas indirect management facilitates, controls, or restricts the activities of direct managers. We applied this framework to the Mariño watershed (Peru) to describe stakeholders' roles using a set of 8 ESs. We have discussed the implications of our findings in terms of equity and power distribution. We conducted face-to-face semistructured interviews with representatives of 52 watershed stakeholders to understand how they managed and benefited from ESs. We used statistical analysis (permutation tests) to detect significant differences in the number of received and managed ESs among stakeholder sectors, i.e., civil society, nongovernmental organizations (NGOs), business, and the public sector, and scales, from local to national levels. Indirect forms of ES management were more frequent than direct ones for all ESs. Water quantity, water quality, and agricultural production were managed by the largest number of stakeholder types. The differences in the number of stakeholder types benefiting from and managing ESs could result from intentional choices, e.g., preferences for local benefits. We also found clear differences in the identity of stakeholders who managed or benefited from ESs. Local stakeholders and the business sector benefited from a higher number of ESs, and public organizations and NGOs were most involved in ES management. More equitable governance of ESs should aim to integrate more diverse stakeholders into decision making. Further empirical research could use our framework to explore the factors determining stakeholders' roles and power distribution. There is a particular need to understand how rights, endowments, and entitlements, as well as spatial configuration, underpin inequities in different social and cultural contexts.

Upscaling instantaneous evapotranspiration retrieved at any specific time-of-day (ETi) to daily evapotranspiration (ETd) is a key challenge in mapping regional ET using polar orbiting sensors. Various studies have unanimously cited the shortwave incoming radiation (RS) to be the most robust reference variable explaining the ratio between ETd and ETi. This study aims to contribute in ETi upscaling for global studies using the ratio between daily and instantaneous incoming shortwave radiation (RSd ∕ RSi) as a factor for converting ETi to ETd.This paper proposes an artificial neural network (ANN) machine-learning algorithm first to predict RSd from RSi followed by using the RSd ∕ RSi ratio to convert ETi to ETd across different terrestrial ecosystems. Using RSi and RSd observations from multiple sub-networks of the FLUXNET database spread across different climates and biomes (to represent inputs that would typically be obtainable from remote sensors during the overpass time) in conjunction with some astronomical variables (e.g. solar zenith angle, day length, exoatmospheric shortwave radiation), we developed the ANN model for reproducing RSd and further used it to upscale ETi to ETd. The efficiency of the ANN is evaluated for different morning and afternoon times of day, under varying sky conditions, and also at different geographic locations. RS-based upscaled ETd produced a significant linear relation (R2 = 0.65 to 0.69), low bias (−0.31 to −0.56 MJ m−2 d−1; approx. 4 %), and good agreement (RMSE 1.55 to 1.86 MJ m−2 d−1; approx. 10 %) with the observed ETd, although a systematic overestimation of ETd was also noted under persistent cloudy sky conditions. Inclusion of soil moisture and rainfall information in ANN training reduced the systematic overestimation tendency in predominantly overcast days. An intercomparison with existing upscaling method at daily, 8-day, monthly, and yearly temporal resolution revealed a robust performance of the ANN-driven RS-based ETi upscaling method and was found to produce lowest RMSE under cloudy conditions. Sensitivity analysis revealed variable sensitivity of the method to biome selection and high ETd prediction errors in forest ecosystems are primarily associated with greater rainfall and cloudiness. The overall methodology appears to be promising and has substantial potential for upscaling ETi to ETd for field and regional-scale evapotranspiration mapping studies using polar orbiting satellites.

This paper is a reflexive analysis of a three-year participatory water research project conducted in the Upper East Region (UER) of Ghana, whose explicit objective was to initiate a multi-level dialogue to support the national Integrated Water Resources Management (IWRM) policy framework. The transdisciplinary team adopted the Companion Modeling approach (ComMod), using role-playing games and a computerized agent-based model to support the identification of a problemshed centered on issues of river bank cultivation, erosion, and flooding, and initiate a multi-level dialogue on ways that this problemshed could be tackled. On the basis of this experience, we identify three key criteria for transdisciplinary research to support innovative water governance: (1) the iterative adaptation of tools and facilitation techniques based on feedback from participants, (2) a common understanding of the objectives pursued and the approach used among researchers, who need to explicit their posture, and crucially, (3) the co-identification of a problemshed that diverse stakeholders are interested in tackling. Finally, we argue that the context in which research is funded and conducted in the development sector constitutes a challenge for researchers to be &ldquo, participants like any other&rdquo, in the projects they coordinate, which constitutes a barrier to true transdisciplinarity.

The objective of this study was to assess the consumption and the multiplier effect of the use of energy and irrigation water for rainfed and irrigated agriculture at the national level in Morocco. Using a social accounting matrix, the direct and indirect economic effects of subsidizing energy used by agriculture were identified. The results show that irrigation water policy in Morocco, which targets 'water-saving' techniques, has increased the use of subsidized energy and that indirect effects, through energy subsidies, exceed the direct effects of agricultural subsidies. A social accounting matrix can help decision makers make the necessary trade-offs between irrigated and rainfed agriculture.

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.

International audience; This essay introduces a collection of articles that explore the future of groundwater-based agriculture in the Mediterranean from an interdisciplinary perspective, in a context of declining water tables due to intensive groundwater use. The imminent crisis that many groundwater economies face due to very rapid and intense global change may have severe irreversible social, economic and environmental consequences, but could also be the opportunity to make a clear break with current agricultural development models and move towards more sustainable agricultural practices. The Mediterranean region is, therefore, an interesting case for the future of intensive groundwater use, as innovative ideas and practices may emerge and inspire similar groundwater-based agricultural systems around the world.

International audience; Much attention has been paid to the issue of groundwater depletion linked to intensive groundwater-based agriculture in (semi-)arid areas. Often referred to as the 'overexploitation' of aquifers, groundwater depletion is generally attributed to the entire agricultural sector without distinguishing between different uses and users. Although it expresses a general concern for future users, the ambiguous term of 'overexploitation' does not acknowledge the contested nature of groundwater use and emerging inequalities. Also, the impact of inequality on groundwater depletion is rarely questioned. The aim of this article is to investigate how and by whom groundwater is depleted, and in turn, how unequal access to groundwater fuels the socioeconomic differentiation of farms and groundwater depletion. Based on a detailed analysis of groundwater use from a user perspective in two irrigated areas in North Africa (Morocco and Algeria), this study shows how the context of groundwater depletion exacerbates'and is exacerbated by'existing inequalities. The paper concludes that knowing how much is withdrawn, where, and by whom provides helpful information for more informed groundwater management by a better understanding of the response of users to declining groundwater conditions and the interests and incentives of different social categories of famers to contribute to groundwater management.

International audience; The aim of this paper is to investigate the notion of collapse of agricultural groundwater economies using the adaptive-cycle analytical framework. This framework was applied to four case studies in southern Europe and North Africa to question and discuss the dynamics of agricultural groundwater economies. In two case studies (Saiss in Morocco and Clain basin in France), the imminent physical or socio-economic collapsewas amajor concern for stakeholders and the early signs of collapse led to re-organization of the groundwater economy. In the other two cases (Biskra in Algeria and Almeria in Spain), collapse was either not yet a concern or had been temporarily resolved through increased efficiency and access to additional water resources. This comparative analysis shows the importance of taking the early signs of collapse into account. These signs can be either related to resource depletion or to environmental and socio-economic impacts. Beyond these four case studies, the large number of groundwater economies under threat in (semi-)arid areas should present a warning regarding their possible collapse. Collapse can have severe and irreversible consequences in some cases, but it can also mean new opportunities and changes.; Le but de cet article est d’explorer la notion d’effondrement des économies agricoles reposant sur l’eau souterraine en utilisant le cadre d’analyse du cycle adaptatif. Ce cadre a été appliqué à quatre cas d’études en Europe du Sud et en Afrique du Nord pour questionner et discuter les dynamiques des économies agricoles reposant sur l’eau souterraine. Dans deux des études de cas (Le Saïss au Maroc et le bassin du Clain en France), l’effondrement imminent (qu’il soit physique ou socio-économique) était une préoccupation majeure pour les parties prenantes et les signes précoces d’effondrement ont conduit à la réorganisation de l’économie reposant sur l’eau souterraine. Dans les deux autres cas (Biskra en Algérie et Almeria en Espagne), l’effondrement n’était soit pas encore une préoccupation, soit il avait été résolu de manière temporaire grâce à une efficacité accrue ou grâce à un accès à des ressources en eau supplémentaires. Cette analyse comparative montre l’importance de la prise en compte des signes précoces d’effondrement. Ces signes peuvent être reliés à un épuisement de la ressource ou aux impacts socio-économiques. Au-delà de ces quatre études de cas, le grande nombre d’économies basées sur l’eau souterraine menacées dans les zones (semi-) arides pourrait constituer un avertissement quant à leur possible effondrement. Cet effondrement peut avoir des conséquences graves et irréversibles dans certains cas, mais il peut aussi représenter de nouvelles opportunités et changements.

The introduction to this book sets out to question why the belief that drip irrigation is a promising technology to save water, modernize agriculture and help the poor remains powerfully intact, despite growing evidence of more contrasted field situations. It pleads for going beyond these narratives to understand the multiple realities of drip irrigation-in-use. This allows showing that drip irrigation is not only a technology but part of broader societal and environmental changes. Unraveling these untold stories raises questions about the accountability and responsibilities over these changes.

Efficient irrigation technologies increase agricultural production and potentially save water. Using the case of modernization projects in a small- scale farmer-managed irrigation system in Morocco, we critically discuss the wisdom of solving problems of water scarcity through technological solutions such as drip irrigation and canal lining. In particular, we show that the promise of future water savings may be used to conceal or postpone contentious political questions of allocation. The water "gains" that newly introduced technologies are expected to yield can be claimed by or promised to many, thereby serving as a strategy to reduce distributional tensions irrespective of whether the water gains are actually realized. (Résumé d'auteur)

Numerous studies have addressed effects of rising atmospheric CO2 concentration on rice biomass production and yield but effects on crop water use are less well understood. Irrigated rice evapotranspiration (ET) is composed of floodwater evaporation and canopy transpiration. Crop coefficient Kc (ET over potential ET, or ETo) is crop specific according to FAO, but may decrease as CO2 concentration rises. A sunlit growth chamber experiment was conducted in the Philippines, exposing 1.44-m2 canopies of IR72 rice to four constant CO2 levels (195, 390, 780 and 1560 ppmv). Crop geometry and management emulated field conditions. In two wet (WS) and two dry (DS) seasons, final aboveground dry weight (agdw) was measured. At 390 ppmv [CO2] (current ambient level), agdw averaged 1744 g m-2, similar to field although solar radiation was only 61% of ambient. Reduction to 195 ppmv [CO2] reduced agdw to 56±5% (SE), increase to 780 ppmv increased agdw to 128±8%, and 1560 ppmv increased agdw to 142±5%. In 2013WS, crop ET was measured by weighing the water extracted daily from the chambers by the air conditioners controlling air humidity. Chamber ETo was calculated according to FAO and empirically corrected via observed pan evaporation in chamber vs. field. For 390 ppmv [CO2], Kc was about 1 during crop establishment but increased to about 3 at flowering. 195 ppmv CO2 reduced Kc, 780 ppmv increased it, but at 1560 ppmv it declined. Whole-season crop water use was 564 mm (195 ppmv), 719 mm (390 ppmv), 928 mm (780 ppmv) and 803 mm (1560 ppmv). With increasing [CO2], crop water use efficiency (WUE) gradually increased from 1.59 g kg-1 (195 ppmv) to 2.88 g kg-1 (1560 ppmv). Transpiration efficiency (TE) measured on flag leaves responded more strongly to [CO2] than WUE. Responses of some morphological traits are also reported. In conclusion, increased CO2 promotes biomass more than water use of irrigated rice, causing increased WUE, but it does not help saving water. Comparability with field conditions is discussed. The results will be used to train crop models.

Climate-smart cropping systems should be designed with three objectives: reducing greenhouse gas (GHG) emissions, adapting to changing and fluctuating climate and environment, and securing food production sustainably. Agriculture can improve the net GHG emissions balance via three levers: less N2O, CH4 and CO2 emissions, more carbon storage, and green energy production (agrifuels, biogas). Reducing the application of mineral N fertilizer is the main option for reducing N2O emissions either directly or by increasing the proportion of legumes in the rotation. The most promising options for mitigating CH4 emissions in paddy fields are based on mid-season drainage or intermittent irrigation. The second option is storing more carbon in soil and biomass by promoting no-tillage (less fuel, crop residues), sowing cover crops, introducing or maintaining grasslands and promoting agroforestry. Breeding for varieties better adapted to thermal shocks and drought is mainly suggested as long-term adaptation to climate change. Short-term strategies have been identified from current practices to take advantage of more favorable growing conditions or to offset negative impacts: shifting sowing dates, changing species, cultivars and crop rotations, modifying soil management and fertilization, introducing or expanding irrigation. Some crops could also move to more suitable locations. Model-based tools and site-specific technologies should be developed to optimize, support and secure farmer's decisions in a context of uncertainty and hazards. Most of the adaptation and mitigation options are going in the same way but tradeoffs will have to be addressed (e. g. increasing the part of legumes will be possible only with significant breeding efforts). This will be a challenge for designing cropping systems in a multifunctional perspective., Des systèmes de culture climato-intelligents doivent combiner (i) réduction des émissions de gaz à effet de serre (GES), (ii) adaptation au changement et à la variabilité climatique et (iii) sécurisation de la production alimentaire. L’agriculture peut améliorer le bilan des émissions de GES via trois leviers : (i) moins d’émissions de N2O, CH4 et CO2, (ii) plus de stockage du carbone, (iii) de la production d’énergie verte (biocarburants, biogaz). Réduire l’application d’engrais minéral ou augmenter la proportion de légumineuses dans la rotation permet de réduire les émissions de N2O. La réduction des émissions de CH4 en riziculture inondée impose de revoir la gestion de l’eau (drainage, irrigation). Stocker plus de carbone dans le sol et la biomasse passe par la culture sans labour (moins d’énergie, paillage avec les résidus de récolte), l’utilisation de plantes de couverture, l’introduction ou le maintien de prairies et la pratique de l’agroforesterie. La sélection de variétés mieux adaptées aux chocs thermiques et à la sécheresse est la principale adaptation à long terme au changement climatique. Des stratégies à court terme ont été identifiées à partir des pratiques actuelles, tirant profit de conditions de croissance plus favorables ou compensant les impacts négatifs par le décalage des dates de semis, l’introduction de nouvelles espèces et cultivars, la diversification des rotations, de nouvelles pratiques de gestion du sol et de la fertilisation, l’introduction ou l’expansion de l’irrigation. Certaines cultures pourraient également migrer vers des zones de culture plus appropriées. Des outils basés sur les modèles et l’agriculture de précision devraient être développés afin d’aider les agriculteurs face à un contexte plus incertain et plus risqué. La plupart des options d’adaptation et d’atténuation sont compatibles, mais des arbitrages devront être faits : ainsi augmenter la part des légumineuses ne sera possible que si des efforts de sélection importants sont conduits.

In a context of water shortage and liberalized land and water markets, peasants have increasing difficulty obtaining access to irrigation. The Chilean state promoted the improvement of irrigation efficiency through the introduction of irrigation technology as a solution to this problem. This chapter analyses the process of state-led technology transfer of drip irrigation in a peasant community in the Limarí Valley (Chile). It reveals a top - down approach to the introduction of technology, in which the state aims to reproduce the dominant social and economic structure. This contributes to a "depeasantization" process because, to obtain access to the technology, the peasants are obliged to adapt to an entrepreneurial mode of farming.

Initially associated with hi-tech irrigated agriculture, drip irrigation is now being used by a much wider range of farmers in emerging and developing countries. This book documents the enthusiasm, spread and use of drip irrigation systems by smallholders but also some disappointments and disillusion faced in the global South. It explores and explains under which conditions it works, for whom and with what effects. The book deals with drip irrigation 'behind the scenes', showcasing what largely remain 'untold stories'.Most research on drip irrigation use plot-level studies to demonstrate the technology’s ability to save water or improve efficiencies and use a narrow and rather prescriptive engineering or economic language. They tend to be grounded in a firm belief in the technology and focus on the identification of ways to improve or better realize its potential. The technology also figures prominently in poverty alleviation or agricultural modernization narratives, figuring as a tool to help smallholders become more innovative, entrepreneurial and business minded. Instead of focusing on its potential, this book looks at drip irrigation-in-use, making sense of what it does from the perspectives of the farmers who use it, and of the development workers and agencies, policymakers, private companies, local craftsmen, engineers, extension agents or researchers who engage with it for a diversity of reasons and to realize a multiplicity of objectives. While anchored in a sound engineering understanding of the design and operating principles of the technology, the book extends the analysis beyond engineering and hydraulics to understand drip irrigation as a sociotechnical phenomenon that not only changes the way water is supplied to crops but also transforms agricultural farming systems and even how society is organized. The book provides field evidence from a diversity of interdisciplinary case studies in sub-Saharan Africa, the Mediterranean, Latin America, and South Asia, thus revealing some of the untold stories of drip irrigation.

The actual performance of drip irrigation (irrigation efficiency, distribution uniformity) in the field is often quite different from that obtained in experimental stations. We developed an approach to explain the actual irrigation performance of drip irrigation systems by linking measured performances to farmers' irrigation practices, and these practices to the underlying logic of farmers who operate these systems. This approach was applied to 22 farms in Morocco. Four sets of variables helped explain the gap between the actual irrigation performance and the performance obtained in experimental conditions: (1) farmers have agro-economic motivations or want to improve their social status, and for them, irrigation performance is at best an intermediate objective. (2) Irrigation performance is not a static value, but a rapidly evolving process, related to the (perceived) ability of farmers to change irrigation practices and renew irrigation equipment, but also to farmers' aspirations. (3) The social network of farmers, supporting the introduction and use of drip irrigation, determines how farmers may share experience, information and know-how related to drip irrigation. (4) Today, there is no social pressure to irrigate carefully to save water; only the state explicitly links the use of drip irrigation to saving water. Making the drip user visible in research and policy studies would lead to more realistic assessments of irrigation performance and draw the attention of policy makers to the actual conditions in which drip irrigation is used, and as a consequence help incorporate 'saving water' as an objective for drip irrigation users.

The Chi River Sub-basin Part II, in Northeast (NE) Thailand, experiences many anthropogenic activities due to the agricultural expansion and intensification, forest deterioration, and a high demand for resource utilization. Land use/land cover change (LULCC) associated with land management, agricultural and conservation practices within the basin can significantly affect hydrologic responses. Like other basins in NE Thailand, the Chi River Sub-basin Part II—comprising more than 60 % of agricultural lands—is characterized by severe floods, droughts, and sedimentation, which directly affect human well-being. Therefore, the objective of this study was to investigate the influences of land management and conservation practices on discharge and sediment yield, and then to develop appropriate management solutions, which could provide alternatives to the current watershed management practices. Three management scenarios—current land use with conservation practices, land use planning (LUP) based on Watershed Classification (WSC), and WSC with conservation practices—were modeled with the Soil and Water Assessment Tool (SWAT), and the results were compared to the existing conditions. The findings indicated that LULCC and conservation practices—conserving the remaining forest, reforestation, applying strip cropping to agricultural land, and channel stabilization by plant cover and engineered constructions—had a little effect on discharge, but greatly influenced the sediment yield. Current land use with the addition of conservation practices resulted in a slight decrease in both total discharge and sediment yield. WSC resulted in a small decrease in discharge, but a dramatic increase in sedimentation. Lastly, WSC together with conservation practices resulted in a slight decrease in discharge and a small increase in sedimentation. These results informed that land management that adopts conservation practices has a strong effect on discharge and sediment yield. A decreased in forest cover when applied WSC resulted in a slight decrease in discharge, but much higher sediment yield. When conservation practices were applied, sediment yield was found to be significantly decreased. Therefore, watershed management should consider LUP, vegetation cover measures, and channel improvements to sustain the Chi River Sub-basin Part II.

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.

ln 2013-14, a farm survey was conducted over 175 small-scale farms to assess the level of diversification and integration of crop-livestock activities in the new reclaimed land (NRL) of Egypt, over a gradient of land reclamation from 1960-2010. In the first years of settlement, crop-livestock systems were mainly developed according to soil type, water availability, accumulated experience and lesson learned from neighbors. Mostly the crop system based on traditional crops; wheat and berseem in the Winter and maize, and vegetable (beanuts and potato) in the Summer. Berseem and maize were for animal fee ding. Livestock included large ruminants (buffaloes and cattle) for milk and meat and small ruminants as a cash flow complement and for social and religious events. ln the areas where common beneficiaries farmers are dominant, they continue to allocate 30-50% of the land to fodder crops. Besides, 46% of university graduates, have rep laced their traditional crop system with fruit tree plantations (mainly oranges); they reduced significantly their livestock activity, as soon as they started to collect fruits; livestock having been the main financial basis for the development of tree systems. The new opportunities of diversification of the crop system through trees in the NRL have supplanted the livestock activity, considered it as a labor intensive activity for graduates, with economic constraint related to feed costs and health issues. ln parallel, the diversification through livestock activities remains a major pillar of farm sustainability for common beneficiaries, in order to face the problems of water availability, and to maintain soil fertility. Behind these different strategies, different challenges can be observed: increase farm income or/and reduce family labor load and/or reduce water and soil risks at the local level. The farm survey shows that the different scale challenges evolve during the settlement according to farm land tenure, past experience and level of education.

During the first half of the 21st century, socioeconomic development is expected to contribute faster and to a greater extent to global water stress than climate change. Consequently, we aimed to identify conditions that can facilitate local adaptation planning for future water security, accounting for the socio-institutional context, developmental needs, and interests affecting water use and management. Our study focused on three forest landscapes in Latin America where water stress was identified as a current concern potentially leading to future social conflict if not addressed. In the three sites, we adopted a participatory approach to implement a systematic diagnostic framework for the analysis of socio-institutional barriers and opportunities influencing local adaptation decision making. This novel application enabled science-society engagement in which civil society organizations were coleading the research. The field methods we used involved participatory social network mapping, semistructured interviews, and validation workshops. Our study generated insights into several interventions that could help overcome barriers affecting the adaptation decision-making process, particularly in the diagnosis and early planning phases. Points of intervention included fostering local participation and dialogue to facilitate coproduction of knowledge, and strengthening the role of key central actors in the water governance networks. These key actors are currently bridging multiple interests, information sources, and governance levels, and thus, they could become agents of change that facilitate local adaptation processes. Working jointly with civil society to frame the research proved effective to increase awareness about water issues, which related not only to the technological, economic, and political aspects of water, but also to organizational processes. The involvement of civil society created genuine interest in building further capacity for climate adaptation and water security. (Resume d'auteur)

Identifying the environmental hot spots of agriculture is crucial in a context where humanity has to produce more food and pollute less. Life Cycle Assessment (LCA) is a powerful tool to evaluate the environmental impacts of agricultural systems, but is still fraught with shortcomings, notably for the evaluation of impacts of freshwater use and of salinisation of water and soil. The core complexity lies in the double status of water and soil resources in LCA which are both a resource and a compartment. The three questions answered by the thesis were: How to better assess the impacts associated with water and salts fluxes? What model should be developed for a relevant inventory of field water and salts fluxes? Is the developed model operational for an LCA study on a perennial crop? The first question was answered through a literature review on salinisation impacts in LCA. It revealed the main environmental mechanisms of salinisation, the factors involved, and discussed the soil and water status, notably through a consistent definition of the technosphere and ecosphere boundary. To answer the second question, a critical analysis of water inventory and agri-food LCA databases showed their inadequacy for the LCA-based ecodesign of cropping systems: they provide estimates of theoretical water consumed, rely on data and methods presenting limitations, and do not support the calculation of both consumptive and degradative water use impacts. For the LCA-based ecodesign of cropping systems, the inventory of water flows should be based on a model simulating evapotranspiration, deep percolation and runoff accounting for crop specificities, pedo-climatic conditions and agricultural managements. For herbaceous crops, the FAO Aquacrop model constitutes a relevant and operational model, but no dedicated model is available to-date for perennials. To fill this gap, a tailored and simple model, so called E.T., was elaborated for the inventory of field water and salt flows for annual and perennial crops. The model combines daily water and salts balances, accounting for soil, climate, agricultural practices and possible crop water and salinity stresses. A first testing of the E.T. model demonstrated its discriminating power for agricultural practices and its robustness. Its validity domain can be extended and its accuracy increased thanks to the recommendations provided. E.T. was also tested in the LCA of a Mandarin grown in Morocco. For most impact categories, electricity use for irrigation was the main contributor revealing a water-energy nexus. Water use had a major contribution to damages for all areas of protection. Overall, to further improve the assessment of impacts due to water use (including salinization impacts) we recommend using a more mechanistic and hydrological approach.

La zone côtière du nord - ouest (NWCZ) de l'Egypte qui s'étend de la frontière du Gouvernorat d'Alexandrie à l'est jusqu'à la frontière libyenne à l'ouest, ne dépend que des précipitations pour ses activités culturales et d'élevage. Cette zone a connu de nombreuses transformations au cours de son histoire, étant considérée comme un grenier à céréales dans les temps anciens (périodes égyptiennes, grecques et romaines) pour devenir une zone à dominante élevage depuis le début du XIe siècle suite à la colonisation par une tribu Awlad Ali originaire de la Lybie. Plus récemment, au cours du vingtième siècle et plus particulièrement dans les années 60 - 70 et ce avec l'appui de grands projets internationaux de développement en lien avec les politiques nationales, les éleveurs bédouins se sont largement investis dans l'agriculture pluviale (principalement l'orge) pour la consommation humaine et animale et aussi l'arboriculture dans les dépressions et le lit des oueds (principalement les plantations de figuiers, oliviers et amandiers). En raison de la faiblesse des précipitations au cours des 50 dernières années, l'arboriculture est devenue une source importante de revenus pour les ménages bédouins. Au cours des quinze années d'observation (de 1995 à 2010), la moyenne annuelle des précipitations a été d'environ 140mm. Ainsi, cette période est considérée par la population locale comme la plus longue période de sécheresse depuis le début du vingtième siècle. La sécheresse a eu plusieurs effets négatifs sur la société bédouine dont les effets les plus cités sont la perte de pâturages et du couvert végétal, la pénurie d'eau, la dégradation des terres, et une réduction du bétail et des activités de culture. Toutefois, cette période de 1995 à 2010 a aussi connu de nombreux autres changements dans les domaines économiques et sociaux, notamment en lien avec la sédentarisation des ménages bédouins et le développement urbain et touristique des villes côtières. Ces changements ont engendré plusieurs opportunités pour les populations locales, notamment des opportunités de travail ou de commercialisation des produits locaux. Plus en lien avec une tradition de mobilité, les jeunes hommes ont continué d'émigrer à la recherche d'un emploi; les principales destinations étant les pays du Golfe et la Libye. Dans le même temps, les projets internationaux se sont intéressés à l'amélioration de la gestion des oueds avec notamment le renforcement des infrastructures d'eau qui ont largement contribué au développement de l'agriculture dans les lits des oueds. Le bassin versant de Naghamish (dit wadi Naghamish), représentant l'un des 218 bassins versants de la zone côtière nord - ouest, a été choisi pour notre zone d'étude. Ce wadi a également été affecté par la période de sécheresse (1995 - 2011). Notre objectif a été de comprendre, voire d'évaluer, les effets de la sécheresse sur l'état des ressources naturelles et la capacité des sociétés bédouines à y faire face voire s'adapter. Pour cela, nous avons mobilisé deux principales approches socio-économiques pour analyser les comportements des ménages, ces approches étant basées respectivement sur des enquêtes semi-structurées et des entretiens ouverts. Les données et informations collectées ont été croisées avec des approches géographiques telles que la télédétection (RS) et le système d'information géographique (SIG) qui nous ont permis d'associer les changements socio-économiques avec les changements sur les ressources naturelles et leur utilisation. Une évaluation hydrologique pour les ressources en eau disponibles a été effectuée dans trois scénarios différents (humide, sec et moyenne) afin de comprendre les processus d'adaptation des familles bédouines au changement des précipitations en intégrant les trois approches socio-économique, géographique et hydrologique. Les résultats montrent que la sécheresse de la période (1995-2010) a causé trois différents types de sécheresse dans la zone d'étude : climatiques, hydrologique et agricole. Au-delà de la multitude des changements observés, la sécheresse a été la principale raison de la baisse des effectifs du cheptel dans la zone d'étude, ainsi que de la diminution de la productivité des cultures at arboricultures, entraînant de nombreuses recompositions des activités au sein des familles bédouines. Ainsi, ont démarré des activités semi-intensives d'engraissement ovin ou d'aviculture ou de nouvelles migrations urbaines dans les secteurs publics. Ces changements d'activités se sont opérés en même temps que des changements de mode de vie liés à l'urbanisation, la modernisation des habitations, le développement des infrastructures et de l'éducation. L'étude montre aussi des changements significatifs dans la couverture végétale entre 1993 et 2011 et une pénurie permanente d'eau en saison sèche quelle que soit l'année climatique. Si les familles bédouines ont réussi à trouver des ajustements familiaux à la sécheresse de 1995-2010, l'absence de stratégies et d'actions collectives constitue un frein important dans la réduction des effets de dégradation des sols et dans la gestion de la ressource eau.

In lowland rice production, water-saving irrigation technologies have been developed, but it has rarely been considered that the absence of a ponded water layer could change the field's microclimate due to the different thermal characteristics of water compared to air. At a site in the Senegal River valley, canopy and soil temperature as well as temperature at meristem level and relative humidity inside the canopy were observed in the presence and absence of a ponded water layer in an irrigated rice field. Gas-exchange measurements were conducted at different development stages of three varieties (IR4630, IR64, and Sahel108) sown in bi-monthly intervals and the effects of climatic and microclimatic parameters on stomatal conductance, assimilation rate, and intrinsic water use efficiency were investigated. Minimum soil ( T s min) and meristem temperature ( T M min) were usually lower in the absence of a ponded water layer. Stomatal conductance depended mainly on T s min, T M min, and minimum relative humidity inside the canopy. Assimilation rate was positively correlated with solar radiation, T s min and T M min, but depended mainly on stomatal conductance. Without standing water, stomatal conductance was significantly lower, but reductions could be explained with lower T s min and/or T M min. Nevertheless, T s min and/or T M min were the major determinants of stomatal conductance and assimilation rate, which suggests a pivotal role of root zone temperature on plant growth probably via water uptake and, thus, overall plant water status. Varietal differences were found, with assimilation rate in IR4630 and Sahel108 having been less affected by low temperature than in IR64. When water-saving irrigation measures are applied in irrigated rice, the negative effects of lower soil and meristem temperature in the absence of a ponded water layer in the field on the productivity of rice need to be considered. In regions where night temperatures below 20 °C occur, varieties should be used that are less temperature-responsive, if the effect of cool nights on meristem temperature cannot be mitigated by a ponded water layer.

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.

Yield reductions have been widely observed under water-saving irrigation in lowland rice. The yield gap has been related to decreases in the number of spikelets per panicle and decreased spikelet fertility. Since these yield components highly depend on the thermal environment of the meristem which is subjected to changes when a ponded water layer is omitted, the impact of irrigation system on yield components needs to be studied under consideration of temperature at meristem level. Therefore, the objective of this study was to analyze yield and yield components of irrigated rice grown with and without a ponded water layer under consideration of effects of irrigation system on meristem temperature under field conditions. Field trials were conducted on two sites in Senegal, where rice was grown under flooded and non-flooded conditions with six staggered sowing dates between August 2009 and June 2010. Temperature was measured at meristem level and related to leaf area, yield and yield components of three different varieties (i.e. IR64, Sahel202 and N22). Yield reductions under non-flooded conditions were mainly observed in the cold-dry season, whereas slight yield increase were found in the hot-wet season. Among the yield components, reduced number of spikelets per panicle and spikelet fertility accounted for the largest share of the yield gap. Meristem temperature during the night was always lower under non-flooded conditions and the temperature difference between irrigation treatments increased during the cold-dry season. Leaf area per tiller was linearly related to meristem temperature in the observed temperature range, and a linear relationship was found between leaf area per tiller and the number of spikelets per panicle. Furthermore, spikelet fertility increased with meristem temperature between panicle initiation and booting stage. Therefore, lower meristem temperature led to smaller leaf area per tiller, less spikelets per panicle and decreased fertility under non-flooded conditions. Without standing water, the rice plant's meristem will be exposed to lower temperatures during night, which can lead to significant yield reductions in areas where cool nights occur.

Erratum paru dans Agricultural Water Management (2013) 127 p. 124-126; International audience; This paper reports on an experiment undertaken in the Office du Niger irrigation scheme (100,000 ha) in Mali, where the unprecedented development of irrigation driven by large scale investors is dramatically increasing uncertainty surrounding future water management. Coping with future uncertainty in irrigated systems is essential but existing approaches based on scenarios and decision support systems are mainly expert-driven, making them difficult for local users to understand and use on their own. The aim of this study was to design a participatory approach to help local and national stakeholders understand the possible future consequences for water management of scenarios they had built themselves in previous workshops. A role playing game called FOWIS (Future of water in irrigated systems) was designed for this purpose. Two groups (decision makers and local actors) took part and played the roles of family farmers, large scale investors, or the manager of the irrigation scheme. Playing FOWIS increased the players' awareness of each others' strategies and of land development issues, crop choices, and water management. In the local actors' group, applying land development strategies and choosing crops while failing to account for the inevitable increase in water demand led to serious water crises: total demand exceeded water availability by 75%, and the indicator of adequacy dropped to 0.5 for many players. In the decision makers' group, applying a collective strategy to limit water demand, as stipulated in their best case scenario, resulted in an equitable water supply. In this paper, we show how the game enabled participants to understand the interdependencies between future land development, crop choices, and water management, and, in addition, helped them design innovative strategies to limit water demand or to allocate water fairly. Indirectly, it also led them to question their current practices, choices and strategies that would have been impossible in the current context of open tensions concerning land and water allocation. The FOWIS experiment also provided useful information for the further development of non-computer-assisted role playing games in highly uncertain contexts, which is the case of most irrigated systems in developing countries. RPGs that take place in a virtual world could increase stakeholders' capacities to take action with respect to real world issues. (Résumé d'auteur)

As the human population continues to grow and competition for natural resources increases, there is a consequent need to produce more food with fewer resources. Flooded rice crops use large quantities of water, which becomes scarcer for farmers. New methods of saving irrigation water have been tested and released but they often suffer from a yield trade-off. A comparative study was carried out with a recent dual-adapted variety cultivated as either a flooded transplanted crop or a direct-seeded and soil water-saturated crop, referred to as an aerobic crop, to dissect the crop physiological differences induced by crop management. Experiments were conducted at IRRI's experiment station in Los Banos, Philippines, in the dry seasons of 2011 and 2012. Grain yields were 2 tons/ha or 25% lower in the aerobic crop as a result of a complex series of modifications and adjustments in plant architecture and yield components. Four main changes - higher plant density, slower rate of leaf appearance, lower nitrogen content, and reduced size of all organs - induced by the aerobic crop environment were responsible for three chains of modifications that resulted in lower biomass accumulation and finally lower grain yield. Leaf appearance rates were bilinear in both environments, initially similar in both environments and slower after an inflection point that occurred at the appearance of the 8th leaf in aerobic crops instead of the 11th leaf in flooded crops. As a consequence, two fewer leaves were produced by main tillers in aerobic crops, whose individual leaf area thus was much lower. In 2012, plant nitrogen content was about 1% lower in the aerobic crop than in the flooded crop during the entire crop duration. Biomass accumulation of the variety used was biphasic in both environments, with high radiation use efficiency during the two phases of effective biomass accumulation in flooded crops, and the standard radiation use efficiency expected with C3 species in aerobic crops during the same phases. (Resume d'auteur)