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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; 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.

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.

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.

International audience; Through economic and geographical cross-disciplinary approaches based on case studies illustrating the current endogenous and exogenous transformations of the use of common resources in Morocco, the aim of this article is to question the evolution of the notion of commons. Is it still relevant to refer to commons when rural communities have frequently lost the power to govern local natural common-pool resources, such as agricultural water, grasslands, or certain types of forests, to the benefit of the state or the private sector? We question the current role of national public authorities who have supported the rise of a production-driven organization, particularly in the context of the “Green Morocco Plan.” Thus, the preservation of natural resources, collective management systems, and traditional expertise have too often been neglected.; À travers les regards croisés de l’économie et de la géographie, et sur la base de plusieurs études de cas démonstratives des transformations en cours au Maroc des usages des ressources communautaires, à la fois endogènes et en lien avec des impulsions extérieures, l’objectif de cet article est d’interroger l’évolution de la notion de communs dans un contexte de crise de ces derniers. Est-il encore possible de parler de communs dans des situations où les communautés rurales se trouvent le plus souvent dessaisies, au profit de l’État et du secteur privé, des prérogatives qui étaient les leurs en matière de gouvernance locale de ressources collectives telles que l’eau agricole, les pâturages ou certaines forêts ? Cette réflexion nous amène à interroger le rôle actuel des pouvoirs publics marocains, notamment dans le cadre du Plan Maroc Vert, qui appuient l’émergence d’un mode d’organisation à vocation productiviste, négligeant trop souvent la préservation des ressources naturelles, des systèmes de gestion et des savoir-faire traditionnels collectifs.

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; Pour obtenir et maintenir une eau potable qui réponde aux normes, les collectivités locales ont le choix entre deux types d’actions : préventives par la mise en place de périmètres de protection de captages d’eau potable (PPC) ou d’aires d’alimentation de captages (AAC), ou/et curatives qui consistent à traiter les eaux pour satisfaire les exigences réglementaires. La mise en place des actions préventives aboutit à l’instauration de prescriptions sur les activités existantes et futures. Cependant, à l’heure actuelle, la procédure de mise en place des périmètres de protection des captages d’eau potable ne prend pas en compte les impacts financiers et économiques des prescriptions, ce qui pose des problèmes d’acceptabilité de cet instrument mais aussi des difficultés méthodologiques pour l’évaluation des impacts des prescriptions, en particulier celles appliquées au secteur agricole. Le but de cette étude est de répondre à la nécessité de prendre en compte le volet financier et économique dans le cadre des procédures préventives. Ainsi, l’étude propose un protocole d’évaluation socio-économique pour améliorer la procédure PPC. Dans le cadre de ce protocole, nous avons mis en place, d’une part, un ensemble complet de données sur les coûts financiers des mesures agricoles et non agricoles appliquées dans le cadre de ces PPC et, d’autre part, une méthode qualitative basée sur l’analyse des coûts et bénéfices supportés par les acteurs impactés par les PPC.

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.

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.

Cet article analyse les interactions entre pratiques locales d'accès à l'eau souterraine et politiques publiques. La plaine du Saiss au Maroc dispose d'un système aquifère qui a permis le développement d'une agriculture intensive à travers des puits et des forages privés, soutenu par des politiques agricoles volontaristes. L'Agence de Bassin pour sa part, attire l'attention des différents acteurs sur les fortes baisses du niveau des eaux souterraines. Ce système aquifère se retrouve ainsi au centre de stratégies diverses pour l'accès à l'eau souterraine et la gestion des ressources disponibles. Nous mettons en exergue les processus qui président à la construction des règles d'accès, d'utilisation et de gestion de la nappe. Entre une situation de libre accès et de compétition (anarchie) et une planification totale (Léviathan), nous avançons qu'il faut reconsidérer la place et le rôle attribués à certains acteurs dans la littérature en tenant compte à la fois de l'échelle locale où s'opèrent des processus multiples, souvent informels, pour l'accès à l'eau souterraine ; et de l'échelle régionale où sont mises en œuvre les politiques publiques régissant le développement agricole et la gestion des eaux souterraines. Plutôt qu'un emboîtement, on observe une hybridation des règles d'accès. L'État n'est pas absent de la régulation de cet accès, bien que celui-ci soit privé et atomisé. This paper aims to analyze interactions between local practices of obtaining private access to groundwater for irrigation, and public policies of groundwater management. The aquifer system in the Saiss plain in Morocco enabled the development of an intensive agriculture, supported by ambitious agricultural policies. At the same time, the River Basin Agency draws attention to the existing overexploitation of groundwater. Thus, the Saiss aquifer is at the centre of diverging strategies for the access to groundwater and the management of available water resources. We analyze the processes presiding over the construction of rules for access, use and management of the aquifer. Challenging the dualistic visions of a context of free access to water resources and unrestricted competition (anarchy) versus a situation of over-control and central planning (Leviathan), we assert that the place and the role conferred to certain actors in the literature should be re-evaluated. This is possible by considering both the local scale with its various (informal) processes for access to groundwater, and the regional scale where policies governing the agricultural development and groundwater management are implemented. Rather than a stacking of rules, we observed a hybridization of these rules.

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)

International audience; 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

International audience; Thermal infrared images can be used to estimate vegetation water content of the plant and thus to locally adapt (precision agriculture) and globally adjust (sustainable management of water resources) irrigation water quantities. Thermal imaging cameras using micro-bolometer sensors loaded on light aerial vehicles are suitable to produce thermal images. These images are helpful for irrigation monitoring if they are: (i) coupled with simultaneous acquisition of images in the visible and near infrared bands; (ii) geometrically corrected to be superimposed with other images; and (iii) radiometrically corrected to take into account the drift of the thermal sensors and the effects of the atmosphere on the measured temperature.

Les agriculteurs en zone irriguée sont confrontés à une pression croissante pour préserver la ressource en eau. Cette situation les amène d'une part, à économiser l'eau en mettant l'accent sur des productions moins consommatrices, d'autre part, à mieux valoriser les quantités utilisées. Plusieurs stratégies sont envisageables comme modifier les choix d'assolement ou adapter les modes de conduite des cultures. Ces stratégies peuvent avoir des conséquences importantes sur l'organisation des filières aval, notamment à l'échelle de bassins d'approvisionnement de l'industrie agro-alimentaire. Cet article propose une analyse des impacts et des conséquences économiques de fortes restrictions d'eau, à l'échelle des filières. Cette analyse a été mise en oeuvre en France sur le cas de la nappe de Beauce, avec la participation des acteurs des filières locales. Elle permet d'analyser les adaptations et les stratégies de chacun face à des baisses de volumes d'eau disponibles. Elle met en évidence les interactions entre les opérateurs d'une même filière et les interactions entre différentes filières.

Introduction De Dakar a Djibouti, la Grande Muraille Verte (GMV), traverse au Nord de l’isohyete 1000 mm les bassins versants des fleuves, Senegal, Niger, Volta, Logone, Chari et Nil. Serpentant entre les paralleles : 15° et 10°Nord, a peu pres a mi-distance entre l’equateur et le tropique du Cancer, elle s’etend sur des versants arides ou semi arides du Sahel, recoupe les bas-fonds de petites rivieres souvent endoreiques et croise les plaines alluviales et les lits des grands fleuves, ou de leurs principaux affluents (fig.1).

I. De la terre. Peut-on la protéger ?; International audience; Comment assurer la sécurité des approvisionnements alimentaires des populations tout en protégeant l'environnement et les ressources naturelles en Méditerranée ? Telle est la question cruciale et difficile à laquelle il faut absolument répondre, comme l'atteste la récurrence des "émeutes de la faim" dans la région lorsque les prix des produits alimentaires, ceux du pain ou de la farine en particulier, augmentent. Les évènements du "Printemps arabe" de 2011, notamment en Tunisie et en Egypte, montrent bien que cette question du prix des produits alimentaires est politiquement très sensible.

The problem of water appears to be the critical path in the analysis of Mediterranean landscapes, especially in Tunisia, where such regions are developed so as to assure better control of water. This study focused on two small watersheds belonging to a network of watersheds defined and followed by the IRD-Tunis within the framework of the AMBRE program. The importance and complementarity between photo-interpretation and ground techniques are emphasized in this work. This article offers answers to certain questions concerning landscape matters by approaching them from the “Science of the landscape” point of view, here meaning the hydrodynamic segmentation of the landscape. The study aims at delimiting and better understanding the organization of landscapes in segments and their hydrodynamic behaviour at the level of the watersheds, as well as the global impact of development on these surroundings. We ask how the landscapes are organized, what their hydrodynamic behaviours are, the impact of development in these Mediterranean surroundings and whether the notion of landscape segmentation, derived from the method of “Science of the landscape,” is pertinent to furthering the understanding of these landscape dynamics., Le problème de l'eau apparaît comme le fil conducteur essentiel de l'analyse des paysages méditerranéens, particulièrement en Tunisie où ces milieux sont entièrement aménagés dans le sens d'une plus grande maîtrise de l'eau. Cette étude a été réalisée sur deux petits bassins-versants situés dans la Dorsale tunisienne, qui font partie d'un réseau de bassins-versants défini et suivi par l'Institut de recherche pour le développement (IRD)-Tunis dans le cadre du programme AMBRE. L'accent est mis sur l'importance et la complémentarité des techniques de photo-interprétation et de terrain. Cet article cherche à apporter des réponses aux questionnements paysagers abordés sous l'angle de la « Science du paysage » – appliquée ici à la segmentation hydrodynamique des paysages. Cette recherche vise à mieux cerner et comprendre l'organisation des paysages en segments, leurs comportements hydrodynamiques à l'échelle du bassin-versant, ainsi que l'impact global des aménagements sur ces milieux. Comment s'organisent les paysages ? Quels sont les comportements hydrodynamiques de ces derniers ? Quel est l'impact de tous les aménagements réalisés dans ces milieux méditerranéens ? La notion de segmentation du paysage, extraite de la méthode de la « Science du paysage » est-elle pertinente dans la compréhension de ces dynamiques paysagères ?

National audience; Confrontés à la chute de la rentabilité de la production céréalière et à celle de la disponibilité en eau d'irrigation, des acteurs-clés du secteur agricole du Bajio (Guanajuato, Mexique) tels que organisations d'usagers de l'irrigation, services de développement, de vulgarisation et de recherche, fabricants d'intrants et de machines, institutions de crédit et de formation décident en 2001 de lancer ASOSID, un nouveau projet inter-institutionnel, dans le but de promouvoir l'agriculture durable à base de semis-direct sur couverture végétale. Sous la houlette d'agronomes-chercheurs de la recherche agronomique internationale (CIRAD et CIMMYT), ASOSID s'est d'abord attaché à construire puis consolider la collaboration entre ses membres autour d'une démarche de construction d'innovations en partenariat (CIP). Suite à la reprise en main vigoureuse du projet par le ministère de l'Agriculture de l'Etat du Guanajuato au bout d'un an, les priorités du projet ASOSID ont été recentrées sur la diffusion massive des tech iques de semis direct déjà disponibles. Pour ce faire, ASOSID est revenu à une démarche conventionnelle de type transfert de technologie, alors que le dispositif CIP était rapidement démantelé. Cette évolution comporte des risques importants de sous-investissement dans la mise au point participative d'innovations sociotechniques et organisationnelles dont l'agriculture régionale a pourtant besoin. Après avoir retracé l'expérience ASOSID, l'article examine l'espace, le temps, les rôles, les négociations et les dispositifs nécessaires à la construction collective et itérative de visions, d'objectifs et de stratégies d'interventions communs à l'ensemble des acteurs impliqués dans la résolution en partenariat de crises complexes d'une agriculture à l'échelle régionale, en insistant sur le rôle des chercheurs dans ces processus

An increasing number of regions have unsustainable groundwater balance due to overdraft. This is most evident in semi-arid areas where intensive irrigated agriculture takes place. In general, agriculture is taking the larger share of water extractions. Therefore, the main objective of policy-makers is to induce a reduction of water use by the agricultural sector to achieve sustainability in aquifer management and also to reallocate water to other sectors. This work studies the impact of water demand-management strategies on small-scale groundwater irrigated systems that are managed by groups of farmers in the Baj´ıo Guanajuatense, centre of Mexico, where intensive irrigated agriculture predominates. Several strategies are considered : economic tools (electricity pricing, electricity quotas, subsidies) on one side, technological change with conservation tillage on the other side. We also paid attention to the impact of institutional settings (collective rules) on the effectiveness of these instruments. Farmers decisions, interacting strategically with other members, are represented by mathematical programming models with a Mixed Complementarity Problem (MCP) structure. The simultaneous optimizations of utility functions of the different interacting members, considering their technical constraints, result in a non-cooperative equilibrium. Non-cooperative and cooperative equilibrium, whereby all farmers would contribute to a unique and additive utility function, are compared. This comparison brings a quantitative perspective to the debate on the respective role of economic incentives versus organizations in addressing natural resources degradation. Results shows that, at current electricity price regime, water consumption by cooperative and non-cooperative wells are not significantly different. However, cooperation does have an effect on water allocation between members. Therefore, institutional change within groups is more likely to have an effect on water allocation that global water consumption, thereby reducing its attractiveness for decision-makers. However, when electricity prices are increased, difference in consumption between cooperative and non-cooperative mode are becoming important. In that context, accompanying changes of institutions will then become necessary and useful. In addition, as water pricing is often considered necessary but politically difficult to implement given consumption inelasticity, we studied the potential of a new rate structure, the uniform price with rebate. We show that this tariff structure allows sending a strong price signal that is effective at changing water consumption. But, with the help of the rebate, it also avoids puncturing the agricultural sector as a whole, but generates transfers between the various types of users. Finally, this work shows that if none of these instruments alone makes it possible to reduce agricultural water demand without affecting farmers seriously, a combination of price level and structure change, as well as technical and institutional changes would bring a coherent solution.; Un nombre croissant d'aquifères ont un déséquilibre marqué entre recharge et demande provoquant un épuisement progressif de la ressource. Ce phénomène est marqué dans les zones semi-arides où une agriculture irriguée intensive s'est développée. La majorité des prélèvements sur ces nappes est imputable à l'agriculture. L'objectif est donc de réduire la consommation brute globale des systèmes de production agricoles au nom de la durabilité et de l'allocation entre les secteurs.Ce travail étudie l'impact des instruments de gestion de la demande en eau sur des petits périmètres irrigués collectifs, ici appelés puits collectifs, d'une région d'agriculture intensive du centre du Mexique. Plusieurs instruments sont considérés : économiques (tarification, quotas, subventions) d'une part, offre technologique d'autre part. Par ailleurs, une part importante est consacrée à l'impact de la configuration institutionnelle (règles collectives) sur les résultats de ces instruments. A l'aide de la programmation mathématique, nous modélisons les décisions individuelles des producteurs en situation d'interactions stratégiques au sein des puits collectifs par une formulation type problème de complémentarité mixte. Cette formulation nous permet de représenter l'optimisation simultanée d'agents en interactions (équilibre de Nash). Nous confrontons les résultats de ce modèle avec ceux d'un puits où le comportement des producteurs est coopératif, i.e. maximisant une fonction d'utilité unique du groupe. Ceci nous permet d'apporter une perspective quantitative au débat sur les rôles respectifs des incitations économiques et des institutions dans la lutte contre la dégradation des ressources naturelles. Notre étude montre qu'au régime de tarification actuel la consommation globale des puits collectifs est peu différentiée entre les modes coopératifs et non-coopératifs. Par contre l'allocation de l'eau entre les différents membres varie entre ces deux modes. Tout travail institutionnel est donc susceptible d'induire une ré-allocation plutôt qu'une réelle diminution du niveau global de consommation, réduisant l'intérêt que pourront porter les décideurs politiques. Cependant, avec un scénario d'augmentation du prix de l'électricité, les écarts de consommations croissants entre les deux équilibres justifient un travail d'accompagnement institutionnel d'une réforme tarifaire. Par ailleurs, l'étude de la tarification uniforme avec remise fixe réhabilite l'outil tarifaire souvent perçu comme nécessaire mais politiquement difficile à mettre en place du fait de l'inélasticité de la consommation des systèmes de production au coût de l'eau. Ce type de tarification évite de ponctionner le secteur agricole dans son ensemble, mais engendre des transferts entre les différents types d'utilisateurs. Au final, ce travail montre que si aucun des instruments pris isolément ne permet d'apporter une solution en termes de diminution de la demande en eau agricole, une combinaison des instruments tarifaires et institutionnels et du changement technique permettrait d'apporter une solution cohérente.

International audience; Le développement de l'irrigation s'est, dans la majorité des situations, accompagné de l'apparition de processus de salinisation, de sodisation ou d'alcalinisation des sols à des degrés d'importance divers. Si les situations apparaissent très variées en raison des caractéristiques du milieu naturel et des modalités de gestion de l'eau et des systèmes de culture, ces dégradations résultent pour l'essentiel de modes de gestion inappropriés dans les systèmes irrigués. En retour, des mesures correctives permettent souvent d'améliorer ces situations qui ne sont donc pas inéluctables. Ces interactions sont analysées sous l'éclairage de situations dont les évolutions ont été similaires en Egypte, au Pakistan, au Mali et au Maroc, présentés lors du séminaire PCSI 2002 : « Vers une maîtrise des impacts environnementaux de l'irrigation », (confort hydrique, remont ée de la nappe, engorgement, salinisation des sols, programme de drainage, raréfaction des eaux de surface de bonne qualité, mobilisation de ressources souterraines, baisse du niveau des nappes, dégradation de la qualité des eaux). La salinisation des sols apparaît aussi comme un indicateur pertinent pour l'évaluation de la performance de ces systèmes irrigués. La période contemporaine est principalement caractérisée par un accroissement de la complexité sous l'influence conjointe d'une libéralisation des pratiques, d'une diversification de la demande et d'une raréfaction des ressources en eau. La mobilisation des eaux souterraines apparaît donc comme une solution intéressante pour les agriculteurs, mais elle s'accompagne aussi de nouvelles menaces sur la conservation des ressources en eau et du sol, et sur la durabilité des systèmes d'irrigation. L'impact réel de l'évolution des sols sur la productivité des systèmes de culture est mal connu. La modernisation de la gestion des systèmes irrigués passe alors par le développement et l'adaptation continue de nouveaux dispositifs pérennes de suivi et d'évaluation et d'outils de pilotage couplant différents critères hydrauliques, agronomiques, organisationnels et environnementaux. Des adaptations des méthodes de pilotage sont nécessaires, mais les responsables ne disposent généralement pas des informations nécessaires, ce qui entraîne des délais et des coûts élevés pour identifier des solutions. Cependant, les indicateurs liés à la salinité des sols sont très utiles car reflètent aussi les performances globales de ces systèmes.

Due to mounting human pressure, stakeholders in northern Thailand are facing crucial natural resources management (NRM) issues. Among others, the impact of upstream irrigation management on downstream agricultural viability is a growing source of conflict, which often has both biophysical and social origins. As multiple rural stakeholders are involved, appropriate solutions should only emerge from negotiation. CATCHSCAPE is a Multi-Agent System (MAS) that enables us to simulate the whole catchment features as well as fanner's individual decisions. The biophysical modules simulate the hydrological system with its distributed water balance, irrigation scheme management and crop and vegetation dynamics. The social dynamics are described as a set of resource management processes (water, land, cash, labour force). Water management is described according to the actual different levels of control (individual, scheme and catchment). Moreover, the model's architecture is presented in a way that emphasises the transparency of the rules and methods implemented. Finally, one simulated scenario is described along with its main results, according to different viewpoints (economy, landscape, water management).

International audience; Face à la prévision de la demande alimentaire mondiale et alors que les Etats souhaitent partiellement se désengager du secteur de l'hydraulique agricole, la durabilité économique des réseaux d'irrigation risque de ne pas être assurée. L'analyse des modes de gestion des Asa, permet de mettre en évidence certaines limites des vastes programmes engagés à travers le monde visant à rétrocéder la gestion des équipements aux associations d'usagers. Cet article montre pourquoi le choix de politiques de financement de la maintenance et du renouvellement des équipements des Asa, tout en étant optimal, n'est pas pour autant durable. Après avoir présenté quelques facteurs explicatifs du choix de politiques de gestion de court terme, nous présentons un modèle inter temporel d'arbitrage entre emprunt et autofinancement. Ce modèle repose sur des caractéristiques macroéconomiques (taux d'inflation, taux d'actualisation et taux d'intérêt des emprunts et de l'épargne) et permet de montrer que les choix de politiques de gestion de court terme sont parfaitement rationnels et optimaux du point de vue des gestionnaires. (Résumé d'auteur)

National audience

International audience