Gestion des ressources en eaux souterraines : sélection d'articles de la 24ème conférence régionale de la Commission Internationale des Irrigations et du Drainage

National audienceCet ouvrage fait la synthèse de l'ensemble des présentations de la 24ème conférence régionale de la CIID sur la gestion des ressources en eau souterraines qui a eu lieu du 14 au 16 mars 2011 à Orléans

Specifying the differentiated contribution of farmers to groundwater depletion in two irrigated areas in North Africa

International audienceMuch 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 The paper concludes that knowing how much is withdrawn, where, and by whom provides helpful information for more informed groundwater management by a better understanding of the response of users to declining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

Usage combiné de jeux de rôles et d'exercices de prospective : une expérience avec des petits agriculteurs Marocains

International audienceMoroccan agriculture is currently undergoing major political, socioeconomic, and environmental transitions. Smallholder farmers involved in large-scale irrigation schemes need to modernize their systems to face these challenges. In this study, a participatory process incorporating different simulation and gaming tools was designed and applied to accompany farmer groups in designing joint irrigation projects, generally drip irrigation systems. A role-playing game was used in the first phase of the process to raise awareness among farmers about the scope and contents of a joint irrigation project and list the different knowledge gaps. During the second phase, a policy simulation exercise based on the actual field situation enabled farmer groups to design their own joint drip irrigation project. As a result, several farmer groups produced a feasibility study for their joint drip irrigation system. Our experience highlighted the complementarity of these tools in a process of change. The abstract role-playing game provided valid learning experience while the realistic simulation supported concrete decision making

La maîtrise de l'irrigation et du drainage pour une gestion durable des périmètres irrigués méditerranéens

[Departement_IRSTEA]EEE [TR1_IRSTEA]22 - IRRISAGE / SALINNational audienceThe Mediterranean countries are experiencing an increase in tensions concerning water resources and, at the same time, they must face problems related to the degradation of their areas. These limitations make it necessary to increase the efficiency of water-use and to create methods and references for the long-term management of water and irrigated zones. In order to test and promote these methods, a Franco-Moroccan cooperation programme has been established in the Gharb zone of Morocco, in association with several French and Moroccan institutions. The seminar on the control of irrigation and drainage for the long-term management of Mediterranean irrigated zones was organized to present the main results obtained within the framework of the cooperation between Cemagref, the National Office for Agriculture in the Gharb Region (ORMVAG) and the Hassan II Agronomic and Veterinary Institute. The seminar also provided the opportunity for sixty Moroccan participants and ten representatives from international organisations to share their experiences.Les pays méditerranéens connaissent des tensions croissantes sur les ressources en eau ; ils ont dans le même temps à faire face à des problèmes de dégradation de leurs périmètres. Ces contraintes rendent nécessaires l'augmentation de l'efficience de l'eau et la mise en place de méthodes et de références pour une gestion durable de l'eau et des périmètres irrigués. Afin de tester et de promouvoir ces méthodes, un programme de coopération franco-marocain a été mis en place dans le périmètre du Gharb au Maroc, en partenariat avec plusieurs institutions marocaines et françaises. Le séminaire sur la maîtrise de l'irrigation et du drainage pour une gestion durable des périmètres irrigués méditerranéens a été organisé pour restituer les principaux résultats obtenus dans le cadre de la coopération entre le Cemagref, l'Office de mise en valeur agricole du Gharb et l'institut agronomique et vétérinaire Hassan II. Le séminaire a également permis de partager l'expérience d'une trentaine d'experts du Bassin Méditerranéen, d'une soixantaine de participants marocains et d'une dizaine de représentants d'organismes internationaux

The blind angle: performance assessment of drip irrigation in use in a large-scale irrigation scheme in Morocco

International audienceThe need for lasting returns on the large investment in state-sponsored drip irrigation projects and the ambitious objectives aimed to achieve requires thorough and continuous assessment of the performance of irrigation systems in use. However, few studies have evaluated the performance of systems once they have been installed, leading to overestimation of actual drip irrigation performance. This study focuses on the Tadla Irrigation Scheme, where a 10 000-ha drip irrigation project had two objectives: improving water productivity and reducing pressure on groundwater resources. The results of the study show a satisfactory but progressively declining distribution uniformity at field level, after 3'4 years of functioning, pointing to potential dysfunction if the equipment is not renewed. The current over-irrigation of crops results in hefty water bills and debts of farmers, no water savings at the field scale, some savings at the scheme scale, but increased tension concerning water delivery. Farmers continued to use groundwater after converting to drip irrigation to avoid surface water shortage. The challenge is to ensure that groundwater is only tapped in exceptional cases to avoid overexploitation. The first step is ensuring more efficient irrigation practices, underlining the need for continuous performance assessment

When groundwater takes over: linking 40 years of agricultural and groundwater dynamics in a large-scale irrigation scheme in morocco

International audienceWhen large-scale irrigation schemes were created, establishing viable, and closely supervised, medium-sized family farms was considered essential to reap the benefits of state investments. This centralized development model was progressively dismantled, especially as farmers installed private tubewells relying less on surface water. Our aim is to analyse development pathways of family farms in the Tadla irrigation scheme (Morocco). Results showed that pathways were linked to groundwater access, but also to (informal) land markets, and off-farm revenues. Groundwater enabled farmers to overcome reductions in surface water, and diversify crops. This concerned mainly the 36% large and medium-sized farms. Such farmers also managed to increase their cropped area through land markets, as renting in land, and producing market crops, require capital. Groundwater showed limited redistributive capacities, as only 20% of small-scale farmers obtained direct access. Farmers' off-farm revenues sustained livelihoods, especially in dry years, but were generally not reinvested in agriculture. Over the past 40years, groundwater has been mainly mobilized from phreatic aquifers, recharged by rainfall and surface irrigation. Their use seems sustainable, but farmers are exploring deeper aquifers while the administration encourages conversion to micro-irrigation, thus reducing aquifer recharge and complicating the future of the groundwater economy

Modélisation de l’irrigation en goutte à goutte enterré du palmier dattier sous les conditions oasiennes

National audienceModeling subsurface drip irrigation for date palm under oasis conditions. Due to its high potential efficiency, subsurface drip irrigation (SDI) was recently introduced in Morocco. This paper deals with its application to the date palm in the Tafilalet oasis (south-east of Morocco), where appropriate design and management of this system have to be proposed to farmers. The objective of this paper is to assess how the variation of the installation depth of an SDI system surrounding a date palm tree can affect the distribution of soil moisture. A numerical model simulating the multidirectional soil water transfer was used to evaluate the distribution of water around the dripper line in the local silty soil conditions. The simulation results using an axisymmetric two-dimensional model were compared to field measurements carried out in a farmer’s plot where SDI was installed at different depths. The study shows the suitability of the model to simulate infiltration around a dripper line during irrigation. Soil moisture is steadier with SDI at 35 cm depth than with SDI at 15 cm and 25 cm. There is an increase in volumetric soil water content below the soil surface for a 35 cm depth, compared to 15 cm and 25 cm, due to less evaporation.En raison de sa bonne efficience potentielle, l’irrigation en goutte à goutte enterré (GGE) a été récemment introduite au Maroc. Ce document discute son utilisation pour le palmier dattier dans l’oasis du Tafilalet (Sud-Est duMaroc), où une conception et une gestion appropriée de ce systèmedoivent être proposées aux agriculteurs. L’objectif de l’article est d’évaluer l’effet de la variation de la profondeur d’installation du systèmeGGEentourant le palmier dattier sur la distributionde l’humidité dans le sol.Pour atteindre cet objectif, un modèle numérique simulant le transfert multidirectionnel de l’eau du sol a été utilisé. Les résultats de la simulation à l’aide d’unmodèle bidimensionnel axisymétriqueont étécomparés à desmesures effectuées sur un sol limoneux, dans la parcelle d’un agriculteur où le GGE a été installé à différentes profondeurs. L’étude montre la pertinence du modèle pour simuler l’infiltration autour d’une rampe enterrée. L’humidité du sol est plus stable avec le GGE à 35 cm de profondeur en comparaison avec une installation à 15 cm ou 25 cm de profondeur. Ily a aussi une augmentation de la teneur en eauvolumique sous la surfacedu sol pour la profondeur de 35 cm, par rapport aux profondeurs de 15 cm et 25 cm, du fait de la diminution de l’évaporation

Laissons les acteurs formaliser les jeux - A propos de l'utilisation de jeux de rôle peu formalisés avec des agriculteurs marocains

A Role Playing Game was developed to prepare farmers for the technical, financial and organisational design of these collective irrigation projects within a larger support package which included individual and collective surveys, information meetings and farmer-to-farmer visits. It was decided to focus the scope of the tool on facilitating the design process. This is why it was decided to adopt a tool with a low degree of formalisation. After a short outline of the context of tool application and its resulting functions and objectives , the article will provide the reasons for this decision that were exchanged during the discussion about the tool's design. They can be found, above all, in the support for stakeholders' knowledge formalisation. The tool itself did not have to endow with a lot of information, but was intended to generate discussion in order to highlight the need for defining management rules and to help farmers formulate these rules. The article then will present a short outline of the resulting design of the tool. Since the Role Playing Game was used for process facilitation in the context of the research project AquaStress, its application is first examined regarding its contribution to the proces

Contribution de la nappe phréatique à l'alimentation hydriquedu palmier dattier (Phoenix dactylifera) dans les zones oasiennes

National audienceIn arid regions, water resources are extremely limited. The contribution of groundwater to satisfy crop water requirements can be very high, but is often not known. This contribution depends on the root zone environment and the water table depth. Understanding the interaction between groundwater tables and plant development is fundamental to improve water use efficiency. The objectives of this paper are to study the effect of shallow water tables on date palm root distribution, and to determine the contribution of groundwater to date palm water consumption. Experimental research was conducted in a farm located in the Tafilalet oasis (Morocco) with Mejhoul palm tree variety. The groundwater depth fluctuated from 4 to 5 m with an average salinity of 5 g.L-1. Many measurements were undertaken to determine soil moisture, roots characterization and transpiration. The results show that during the dry season (June, July and August), and without irrigation supply, 50% of date palm transpiration is satisfied by groundwater. The results also revealed that the root system of date palm tree can reach very important depth (up to 9 m) to withdraw water from the aquifer. Therefore, the determination of palm tree water requirements has to take into account the interaction of its root system with the phreatic water table.Dans les régions arides, les ressources en eau sont extrêmement limitées. La contribution de la nappe phréatique pour satisfaire les besoins en eau des cultures, en particulier le palmier dattier, peut être très importante dans ces zones, mais est souvent méconnue. Cette contribution dépend de l'environnement de la zone racinaire et de la profondeur de la nappe phréatique. Comprendre l'interaction entre la nappe phréatique et le développement du palmier dattier est essentiel pour améliorer l'efficience de l'utilisation de l'eau. Les objectifs de cet article sont d'étudier l'impact de la nappe phréatique peu profonde sur la distribution racinaire du palmier dattier et de déterminer la contribution de cette nappe à sa consommation en eau. Une expérimentation a été menée chez un agriculteur dans une exploitation de palmiers dattiers (variété Mejhoul) située dans l'oasis de Tafilalet (Maroc). La profondeur du niveau piézométrique varie entre 4 et 5 m avec une salinité moyenne de 5 g.L-1 . De nombreuses mesures ont été faites : suivi de l'humidité du sol, cartographie de la distribution du système racinaire et mesure de transpiration. Les résultats montrent que, pendant la saison sèche (juin, juillet et août), et sans apport d'irrigation, 50 % de la transpiration du palmier dattier provient des eaux souterraines. Les résultats révèlent également que le système racinaire du palmier dattier peut atteindre des profondeurs très importantes (jusqu'à 9 m) pour prélever l'eau de la nappe phréatique. Par conséquent, la détermination des besoins en eau du palmier dattier doit prendre en compte l'interaction de son système racinaire avec la nappe phréatique

Accompagner la transformation de l'eau de l'Etat à l'eau communautaire : leçons tirées d'une démarche d'apprentissage social lors de la co-conception de périmètres collectifs d'irrigation

International audienceThis paper focuses on the evaluation of a participatory approach aimed at supporting groups of small-scale farmers in the design of joint drip irrigation projects. Our idea was to create a sustainable social learning environment in which they could acquire adaptive knowledge about new irrigation technology and about designing and managing a joint irrigation project while at the same time improving their negotiation capacities. We developed a framework to evaluate the process as well as the outputs and outcomes of the use of our approach with four groups of smallholder farmers in the Tadla irrigation scheme in Morocco. Our findings showed that the learning environment made it possible to compensate for the knowledge differential among stakeholders and to co-produce knowledge that can be mobilized by smallscale farmers to help them make better informed decisions when choosing whether or not to engage in a joint irrigation project and when developing and implementing such a project. We expect that this will ultimately contribute to supporting the shift from state water to community water through a shared understanding of the technical, economic, and social issues and options related to the management of irrigation water