The 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. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.

Immergés en hiver, les marais saisonniers (merjas) de la plaine du Gharb au Maroc étaient traditionnellement exploités pour le pâturage en été, à côté d’autres usages productifs. Pourtant, ils étaient considérés par l’administration coloniale comme des milieux insalubres et peu valorisés, malgré leur abondance en ressources naturelles. Au cours du XXe siècle, la plaine a fait l’objet d’un aménagement hydro-agricole, incorporant les merjas, pour contribuer aux objectifs nationaux de sécurité alimentaire et d’exportation de produits agricoles. Cet article interroge le regard porté par les acteurs locaux et institutionnels sur les merjas et les bénéfices qu’elles procurent, à travers une analyse des services écosystémiques. Si les institutions les considèrent comme des terres vierges à aménager et des zones tampon de régulation des crues pour protéger les secteurs aménagés et les villes, les collectivités riveraines les considèrent comme des espaces productifs, défavorisés par les crues. L’étude montre des visions contrastées des services écosystémiques, où chaque acteur a une vision utilitariste des merjas. Malgré le débat international sur la biodiversité et le stockage de carbone dans les zones humides, les dimensions écologiques sont peu citées. L’approche par les services écosystémiques dévoile les antagonismes entre acteurs, mais peut être un moyen de négociation sur le devenir des merjas dans une vision territoriale.

The availability of water for agricultural production is under threat from climate change and rising demands from various sectors. In this paper, a simulation-optimization model for optimizing the irrigation schedule in the Bilate watershed was developed, to save irrigation water and maximize the yield of deficit irrigation. The model integrated the Soil and Water Assessment Tool (SWAT) and an irrigation-scheduling optimization model. The SWAT model was used to simulate crop yield and evapotranspiration. The Jensen crop-water-production function was applied to solve potato and wheat irrigation-scheduling-optimization problems. Results showed that the model can be applied to manage the complicated simulation-optimization irrigation-scheduling problems for potato and wheat. The optimization result indicated that optimizing irrigation-scheduling based on moisture-stress-sensitivity levels can save up to 25.6% of irrigation water in the study area, with insignificant yield-reduction. Furthermore, optimizing deficit-irrigation-scheduling based on moisture-stress-sensitivity levels can maximize the yield of potato and wheat by up to 25% and 34%, respectively. The model developed in this study can provide technical support for effective irrigation-scheduling to save irrigation water and maximize yield production.

The Gharb plain in Morocco suffers from water excess in winter and from water deficit during the spring and summer. This explains the low profitability of the investments in irrigation agreed by the Moroccan state and low yields of winter crops. Furrow irrigation systems may be a way to increase water productivity by improving the surface drainage in winter, and by irrigating the crops efficiently in spring and summer. The aim of this study was to assess the hydraulic performance of furrow systems and its agronomic impacts based on an experimental and a modelling approach. Yields were simulated for a series of 11 climatic years (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006). Results clearly showed the advantage of the furrow system whatever the sowing dates. These results confirmed that to improve the water productivity of winter crops in the context of the Gharb scheme, attention has to be paid to surface drainage. RÉ SUMÉLa plaine du Gharb au Maroc souffre des excès d'eau durant la période hivernale et d'un déficit hydrique durant la période estivale. Cet état de fait explique les faibles rendements obtenus des cultures et par là même la rentabilité des investissements entrepris par l'Etat. L'irrigation à la raie peut être une solution adéquate pour améliorer les conditions de drainage de surface durant l'hiver. Elle présente en outre de bonnes performances pour l'irrigation durant la période estivale. Cet article propose, à travers deux approches basées sur l'expérimentation et la modélisation, d'évaluer les performances hydrauliques de l'irrigation à la raie et les impacts agronomiques résultant de l'utilisation de cette technique. La simulation des rendements sur une série climatique de onze années (1995-2006) a clairement démontré l'avantage de la technique d'irrigation à la raie quelque soit la date de semis. Ce résultat confirme l'attention à accorder au drainage de surface pour améliorer la productivité de l'eau pour les cultures d'hiver dans le contexte de la plaine du Gharb. Irrigation à la raie: une technique pour l'amélioration du drainage et de la valorisation de l'eau dans la plaine du Gharb au Maroc.

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.