Quelles distributions spatiales des systèmes de culture pour limiter l'occurence des crises de gestion quantitative de l'eau ? Une démarche de conception évaluation sur le territoire irrigué de l'Aveyron aval

Dans les territoires irrigués exposés aux crises de gestion quantitative de l’eau, la sévérité des étiages dépend des interactions entre systèmes de culture, situations pédoclimatiques, hydrologie, lâchers d’eau et restriction d’irrigation. Dans de nombreuses situations, l’absence de nouvelles solutions de stockage et les tensions entre gestionnaires et usagers de l’eau rendent nécessaire la planification des étiages. Mes travaux explorent le potentiel de « la gestion spatiale » de l’eau pour mettre en adéquation la dynamique des prélèvements pour l’irrigation avec celle de l’offre en eau disponible (naturelle et stockée). Je propose une méthodologie participative de conception-évaluation d’organisations territoriales des activités agricoles, déployée sur l’aval du bassin versant de l’Aveyron (800 km²), en trois étapes: (1) modéliser le système socio-agro-hydrologique, (2) concevoir des alternatives de distribution spatiale des systèmes de culture, (3) conduire une évaluation intégrée des alternatives face à la variabilité climatique observée. Ces travaux combinent des méthodes, connaissances et outils « hard and soft », et font usage de la plateforme de simulation multi-agent MAELIA. Le processus a permis de formaliser des visions d’acteurs et de poser les bases d’une concertation multi acteur. Cependant la simulation des impacts de ces alternatives a montré leurs limites pour régler le problème de déficit structurel en eau. Cette démarche pourrait être prolongée pour aboutir à des propositions opérationnelles

Quelles distributions spatiales des systèmes de culture pour limiter l'occurence des crises de gestion quantitative de l'eau ? Une démarche de conception évaluation sur le territoire irrigué de l'Aveyron aval

Dans les territoires irrigués exposés aux crises de gestion quantitative de l’eau, la sévérité des étiages dépend des interactions entre systèmes de culture, situations pédoclimatiques, hydrologie, lâchers d’eau et restriction d’irrigation. Dans de nombreuses situations, l’absence de nouvelles solutions de stockage et les tensions entre gestionnaires et usagers de l’eau rendent nécessaire la planification des étiages. Mes travaux explorent le potentiel de « la gestion spatiale » de l’eau pour mettre en adéquation la dynamique des prélèvements pour l’irrigation avec celle de l’offre en eau disponible (naturelle et stockée). Je propose une méthodologie participative de conception-évaluation d’organisations territoriales des activités agricoles, déployée sur l’aval du bassin versant de l’Aveyron (800 km²), en trois étapes: (1) modéliser le système socio-agro-hydrologique, (2) concevoir des alternatives de distribution spatiale des systèmes de culture, (3) conduire une évaluation intégrée des alternatives face à la variabilité climatique observée. Ces travaux combinent des méthodes, connaissances et outils « hard and soft », et font usage de la plateforme de simulation multi-agent MAELIA. Le processus a permis de formaliser des visions d’acteurs et de poser les bases d’une concertation multi acteur. Cependant la simulation des impacts de ces alternatives a montré leurs limites pour régler le problème de déficit structurel en eau. Cette démarche pourrait être prolongée pour aboutir à des propositions opérationnelles. ABSTRACT : In irrigated landscapes exposed to quantitative water management crisis, the intensity of low flows depends on interactions between cropping systems, pedoclimatic situation hydrology, water releases and withdrawal restrictions. In many situations there are no opportunities for more water storage, thus tensions occur between water managers and users, which makes the planning of water demand dynamics necessary. My work explores the potentials in the “spatial management of water” to align the water demand dynamics with natural and stored water availability. I present a 3 step, participatory method to design and assess agricultural landscapes: (1) model the Social-Agro Hydrological system, (2) design alternative spatial distribution of the cropping systems, (3) carry an integrated assessment of those alternatives based on observed climatic variability. This method combines “hard” and “soft” methods, knowledge and tools, and uses the MAELIA multi-agent simulation platform. I tested the method tested in the downstream area of the Aveyron River (800 km² Southwestern France). It allowed to formalize the actors’ visions on alternative distributions of the cropping systems. However they showed to be limited in solving the water deficit issue. The method could be continued to reach operational proposals

Analyse participative des compromis entre les services écosystémiques de la zone humide dans la vallée de GaMampa, Province du Limpopo, Afrique du Sud. Leçons pour la gestion des ressources visant la durabilité de la zone humide

The GaMampa wetland is located in the Olifants River catchment, in the Limpopo province of South Africa. It traditionally supports livelihoods, mainly through natural vegetation collection for food provisioning and raw materials. Since the 1990's, and most intensively from 2000 to 2005, it has been drained and its natural vegetation cut and burnt for subsistence maize cultivation. Its ecological integrity is jeopardized. The sustainability of the biological and geomorphologic features, as well as traditional provisioning and contemporary farming opportunities, are questioned. In a diagnosis of the situation, the research identified the reasons for this sudden change in wetland use. Starting from existing data on the case study, mostly developed under the CPWF and WETwin projects, this study analyzed the possible management responses to the problems of the wetland, emphasizing the need for integration of the wetland to the GaMampa valley resource system and thus the need for a global management of the resources aiming at wetland sustainability. This report provides details on management options and their alternatives for implementation, developed through consultation of stakeholders. It also proposes 4 sets of Management Solutions which can be used both by the WETwin project for future research purposes and the GaMampa valley decision makers to establish a management plan

What alternative cropping systems spatial distributions to limit the risk of quantitative water management crises ? A design and assessment method for an irrigated landscape in the lower reaches of the Aveyron River

Dans les territoires irrigués exposés aux crises de gestion quantitative de l’eau, la sévérité des étiages dépend des interactions entre systèmes de culture, situations pédoclimatiques, hydrologie, lâchers d’eau et restriction d’irrigation. Dans de nombreuses situations, l’absence de nouvelles solutions de stockage et les tensions entre gestionnaires et usagers de l’eau rendent nécessaire la planification des étiages. Mes travaux explorent le potentiel de « la gestion spatiale » de l’eau pour mettre en adéquation la dynamique des prélèvements pour l’irrigation avec celle de l’offre en eau disponible (naturelle et stockée). Je propose une méthodologie participative de conception-évaluation d’organisations territoriales des activités agricoles, déployée sur l’aval du bassin versant de l’Aveyron (800 km²), en trois étapes: (1) modéliser le système socio-agro-hydrologique, (2) concevoir des alternatives de distribution spatiale des systèmes de culture, (3) conduire une évaluation intégrée des alternatives face à la variabilité climatique observée. Ces travaux combinent des méthodes, connaissances et outils « hard and soft », et font usage de la plateforme de simulation multi-agent MAELIA. Le processus a permis de formaliser des visions d’acteurs et de poser les bases d’une concertation multi acteur. Cependant la simulation des impacts de ces alternatives a montré leurs limites pour régler le problème de déficit structurel en eau. Cette démarche pourrait être prolongée pour aboutir à des propositions opérationnelles.In irrigated landscapes exposed to quantitative water management crisis, the intensity of low flows depends on interactions between cropping systems, pedoclimatic situation hydrology, water releases and withdrawal restrictions. In many situations there are no opportunities for more water storage, thus tensions occur between water managers and users, which makes the planning of water demand dynamics necessary. My work explores the potentials in the “spatial management of water” to align the water demand dynamics with natural and stored water availability. I present a 3 step, participatory method to design and assess agricultural landscapes: (1) model the Social-Agro Hydrological system, (2) design alternative spatial distribution of the cropping systems, (3) carry an integrated assessment of those alternatives based on observed climatic variability. This method combines “hard” and “soft” methods, knowledge and tools, and uses the MAELIA multi-agent simulation platform. I tested the method tested in the downstream area of the Aveyron River (800 km² Southwestern France). It allowed to formalize the actors’ visions on alternative distributions of the cropping systems. However they showed to be limited in solving the water deficit issue. The method could be continued to reach operational proposals

Réconcilier les moyens de subsistance avec l'intégrité des écosystèmes dans la zone humide de Ga-Mampa, Afrique du Sud

International audienceThe Ga-Mampa wetland is an example of the many small wetlands used for multiple purposes in South Africa. Over the last 15 years it has been progressively converted to subsistence cropping, with negative impacts on its ecosystem integrity. Stakeholders at local and higher scales have different views on the ways to mitigate the impacts of current uses while enhancing local communities’ livelihoods. A participatory decision support framework was developed under the WETwin project to assess the trade-offs between wetland ecosystem services provision and ecosystem integrity and to support wetland planning and management. This paper reports its application to the case of Ga-Mampa wetland, where a particular focus was given to stakeholder involvement in the assessment process. The participatory multi-criteria analysis allowed initiating and strengthening dialogue between very diverse stakeholders, from local to national levels. It also provided reflective material for decision makers in the form of a diagnosis of stakes, and documented management options adapted to the situation and validated by stakeholders. The process itself was more useful than its outcome, raising external stakeholders’ awareness of the complexity of the socio-ecological system and accompanying local farmers in building their own project

Toward integrated water and agricultural land management: participatory design of agricultural landscapes

International audienceOne of the great challenges of developing sustainable water management is to integrate water and land use issues, and to favor stakeholders’ involvement in the process of designing a solution to the specific issues of water basins. This study aims to help reach these objectives: we present the outcomes of a methodology that aims to design, with stakeholders of a watershed facing quantitative water manage- ment issues, alternative agricultural landscapes that they each consider as potential solutions. Our design approach combines (1) facilitation of participatory workshops for designing changes in cropping systems and their spatial distributions at the landscape level with (2) formalization of these alternatives in a GIS. The formalized alternatives provide precise information about fields, farms and areas concerned by the designed changes. We present two sample results of this methodology implemented in a 840 km2 irri- gated landscape located in a water-deficient watershed in southwestern France. We discuss how our design approach may be useful for a wider design-and-assessment methodology involving researchers and stakeholders with conflicting interests. We show that our co-design approach provides fertile ground for the emergence of salient, credible and legitimate change options

The soil-crop models STICS and AqYield predict yield and soil water content for irrigated crops equally well with limited data

Climate-change scenarios predict increased scarcity of water available for agriculture in irrigated regions. To design and assess cropping system adaptations to more frequent droughts, soil-crop models are useful and efficient. The variety of models available makes it difficult to select one that is robust under a wide range of agro-pedoclimatic contexts and effective with limited input data and standard values. Here, we compared performances of two soil-crop models of contrasting complexity: STICS, a mechanistic model, and AqYield, which is much simpler and more empirical. For this purpose, predicted soil water contents and yields were compared to independent data acquired for three spring crops (maize, sunflower, and sorghum) at four sites in a summer-water-deficient region in southwestern France. Crops were grown under several irrigation strategies, from rainfed to full irrigation conditions. Both models tended to predict yields satisfactorily, but more accurately for maize, intermediate for sorghum and less accurately for sunflower. They accurately ranked situations according to crop, soil and irrigation strategy, but failed to rank inter-annual variability. Both AqYield and STICS predicted much of the variability observed in soil available water content (AWC) under maize and sorghum. Predictions were less accurate, although satisfactory, for sunflower. STICS underpredicted AWC under sorghum, but was generally more accurate than AqYield in situations with low water stress. AqYield was more accurate for high levels of water stress, but tended to overpredict AWC. Yearly dynamics of AWC were evaluated with a novel expert method. Both models accurately represented these dynamics in more than 60% of cases. Overall, we demonstrated that both models sufficiently predicted yield and water balance; however, STICS is more appropriate when other limiting processes need to be simulated

Gestion quantitative de l'eau en territoires irrigués: intérêt et contraintes du numérique aux différentes échelles de décision

La gestion quantitative de l’eau est un enjeu majeur, en particulier dans les territoires ruraux où l’activité agricole est soutenue par l’irrigation alors même que la ressource en eau est peu abondante. Cet article présente, à partir de 3 exemples (modélisation intégrée, données satellitales, compteurs communicants), tout l’intérêt du numérique pour gérer l'eau et prendre des décisions en amont et pendant la campagne d’irrigation. Il illustre également les besoins et contraintes techniques associés à l'usage du numérique. Il conclut sur l’importance du facteur humain pour rendre effectifs les atouts du numérique