Disentangling the complexity of groundwater dependent social-ecological systems

Groundwater resources are part of larger social-ecological systems. In this chapter, we review the various dimensions of these complex systems in order to uncover the diversity of elements at stake in the evolution of an aquifer and the loci for possible actions to control its dynamics. Two case studies illustrate how the state of an aquifer is embedded in a web of biophysical and sociopolitical processes. We propose here a holistic view through an IGM-scape that describes the various possible pathways of evolution for a groundwater related social-ecological system. Then we describe the elements of this IGM-scape starting with physical entities and processes, including relations with surface water and quality issues. Interactions with society bring an additional layer of considerations, including decisions on groundwater abstraction, land use changes and even energy related choices. Finally we point out the policy levers for groundwater management and their possible consequences for an aquifer, taking into account the complexity of pathways opened by these levers

Using a furrow system for surface drainage under unsteady rain

Water excess during winter limits crop development on heavy clay soil conditions of the Gharb valley (Morocco). The furrow system to eliminate these negative effects is the adopted solution. This article focuses on the development of a water transfer model through a furrow system during unsteady rainfall event to evaluate the runoff volume resulting from a reference rainy event. This model contains a production function associated to a transfer function. The production function is based on the Green-Ampt infiltration equation. The latter has been adapted to account for unsteady rain conditions and rainfall intermittence. The transfer function is based on the kinematic wave model, the explicit solution of which is coupled with the water excess generated by the production function. Simulated runoff in the furrows is collected by a drainage ditch evacuating the flow outside a plot of 1.3 ha. The similarity between parameters of a furrow irrigation model and those of the production function is advantageously used for model calibration. The proposed modelling approach shows capabilities to predict water amount and peak discharges evacuated from a plot of around I ha by a furrow system under unsteady rainfall events. As an application, it is used to evaluate the ability of the surface drainage system to evacuate the excessive volumes of water under typical rainfalls

Modelling of berseem (Trifolium Alexandrinum) growth and biomass yield under different levels of water stress in Tadla, Morocco

This work compares the performance of PILOTE, an operative crop model developed by IRSTA Montpellier France, with that of well established model, CropSyst, in simulating berseem (Trifolium Alexandrinum L.) growth under different water regimes in the semi-arid climate of Tadla (Morocco). Both based on Beer’s law via the intercepted potential active radiation (IPAR) regarding dry matter accumulation, the models differ in the level of complexity describing crop development, biomass growth, root water uptake principle and consequently, in the number of input parameters. The models were calibrated on an unstressed irrigation treatment in 2009/10, and were validated on other stressed and unstressed treatments in 2009/10 and 2010/11. Although PILOTE required fewer input parameters and data than CropSyst, it performed similarly better when simulating both biomass and soil water balance. The use of different numbers of parameters and crop growth modules by the tested models did not influence substantially the simulation results. Therefore, for management purposes and in conditions of limited input information, the use of simpler models should be encouraged

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

Silage maize growth simulation using pilote and cropsyst model

Models simulating the effects of water stress on crop growth can be valuable tools for improving water management. PILOTE, an operative crop model, and CropSyst, a more sophisticated one, are compared on the basis of the simulation of silage maize (Zea maize L.) growth for 2years (2009-2010) under different water supply regimes in the semi-arid climate of Tadla (Morocco). Both based on Beer's law via the intercepted potential active radiation (IPAR) regarding dry matter accumulation, the models differ in the level of complexity describing crop development, biomass growth, root water uptake principle and consequently, in the number of input parameters. The models were calibrated on an unstressed irrigation treatment in 2009, and were validated on other stressed and unstressed treatments in 2009 and 2010. Although PILOTE required fewer input parameters and data than CropSyst, it performed similarly and often better when simulating both biomass and soil water balance. Therefore, for water management purposes only, the use of a simpler model such as PILOTE can be recommended. © 2013 John Wiley & Sons, Ltd

Economic efficiency of production systems in the Gharb irrigated area (Morocco) affected by access to water resources

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