Sami Bouarfa

Considering groundwater use to improve the assessment of groundwater pumping for irrigation in North Africa

Groundwater resources in semi-arid areas and especially in the Mediterranean face a growing demand for irrigated agriculture and, to a lesser extent, for domestic uses. Consequently, groundwater reserves are affected and water-table drops are widely observed. This leads to strong constraints on groundwater access for farmers, while managers worry about the future evolution of the water resources. A common problem for building proper groundwater management plans is the difficulty in assessing individual groundwater withdrawals at regional scale. Predicting future trends of these groundwater withdrawals is even more challenging. The basic question is how to assess the water budget variables and their evolution when they are deeply linked to human activities, themselves driven by countless factors (access to natural resources, public policies, market, etc.). This study provides some possible answers by focusing on the assessment of groundwater withdrawals for irrigated agriculture at three sites in North Africa (Morocco, Tunisia and Algeria). Efforts were made to understand the different features that influence irrigation practices, and an adaptive user-oriented methodology was used to monitor groundwater withdrawals. For each site, different key factors affecting the regional groundwater abstraction and its past evolution were identified by involving farmers’ knowledge. Factors such as farmer access to land and groundwater or development of public infrastructures (electrical distribution network) are crucial to decode the results of well inventories and assess the regional groundwater abstraction and its future trend. This leads one to look with caution at the number of wells cited in the literature, which could be oversimplified.RésuméLes ressources en eau souterraine dans les zones semi-arides et surtout en Méditerranée font face à une demande croissante pour l’agriculture irriguée et, dans une moindre mesure, pour les usages domestiques. En conséquence, les réserves d’eau souterraines sont affectées et les diminutions des niveaux piézométriques sont largement observées. Cela conduit à de fortes contraintes d’accès aux eaux souterraines pour les agriculteurs, tandis que les gestionnaires s’inquiètent de l’évolution future des ressources en eau. Un problème courant pour l’élaboration des plans de gestion des eaux souterraines est la difficulté d’évaluer les prélèvements individuels d’eau souterraine à l’échelle régionale. Prévoir les tendances futures de ces prélèvements d’eau souterraine est encore plus difficile. La question fondamentale est de savoir comment évaluer les variables du bilan hydrique et leur évolution lorsqu’elles sont profondément associées aux activités humaines, elles-mêmes guidées par d’innombrables facteurs (accès aux ressources naturelles, politiques publiques, marché, etc.). Cette étude fournit quelques réponses possibles en se concentrant sur l’évaluation des prélèvements d’eau souterraine pour l’agriculture irriguée dans trois sites en Afrique du Nord (Maroc, Tunisie et Algérie). Des efforts ont été faits pour comprendre les différentes caractéristiques qui influencent les pratiques d’irrigation, et une méthodologie adaptative centrée sur les utilisateurs a été utilisée pour le suivi des prélèvements d’eau souterraine. Pour chaque site, différents facteurs clés affectant l’exploitation des eaux souterraines au niveau régional et leur évolution passée ont été identifiés en faisant appel aux connaissances des agriculteurs. Des facteurs tels que l’accès des agriculteurs aux terres et aux eaux souterraines ou le développement d’infrastructures publiques (réseau de distribution électrique) sont essentiels pour décoder les résultats des inventaires des puits et évaluer l’exploitation régionale des eaux souterraines et leur évolution future. Cela nous conduit à relativiser les relations entre puits et prélèvements dans la littérature, pouvant être très simplificatrices.ResumenLos recursos de agua subterránea en las zonas semiáridas y especialmente en el Mediterráneo se enfrentan a una creciente demanda para el riego en agricultura y, en menor medida, para usos domésticos. En consecuencia, las reservas de agua subterránea se ven afectadas, observándose una amplia profundización de la capa freática. Esto conduce a fuertes limitaciones en el acceso al agua subterránea para los agricultores, mientras que los gestores se preocupan por la evolución futura de los recursos hídricos. Un problema común para la construcción de planes adecuados para el manejo de agua subterránea es la dificultad de evaluar las extracciones individuales de agua subterránea a escala regional. Predecir las tendencias futuras de estas extracciones de aguas subterráneas es aún más difícil. La pregunta básica es cómo evaluar las variables del balance hídrico y su evolución cuando están profundamente vinculadas a las actividades humanas, impulsadas por innumerables factores (acceso a recursos naturales, políticas públicas, mercado, etc.). Este estudio proporciona algunas posibles respuestas centrándose en la evaluación de las extracciones de agua subterránea para el riego en la agricultura en tres lugares del norte de África (Marruecos, Túnez y Argelia). Se realizaron esfuerzos para comprender las diferentes características que influyen en las prácticas de riego y se utilizó una metodología adaptativa orientada al usuario para monitorear las extracciones de agua subterránea. Para cada sitio, se identificaron diferentes factores clave que afectaron la captación regional de agua subterránea y su evolución pasada, involucrando el conocimiento de los agricultores. Factores como el acceso de los agricultores a la tierra y al agua subterránea o el desarrollo de infraestructuras públicas (red de distribución eléctrica) son cruciales para decodificar los resultados de los inventarios de pozos y evaluar la captación regional de agua subterránea y su tendencia futura. Esto lleva a mirar con precaución el número de pozos citados en la literatura, lo cual podría estar demasiado simplificado.摘要在半干旱地区、尤其是在地中海地区,灌溉农业以及家庭用水对地下水资源的需求日益增长,只是家庭用水的程度较小。因此,地下水的储量受到影响,地下水位广泛下降。这导致农民获取地下水受到极大限制,而管理着担心地下水资源未来的演化。在制定适当的地下水管理计划中,常见的问题就是评价区域尺度上单个地下水抽取量非常困难。预测这些地下水抽取量的未来趋势甚至更具挑战性。基本问题就是在水平衡变量与人类活动紧密相连的情况下怎样评价水平衡变量及其演化,而这些人类活动受到无数因素的左右 (自然资源的获取、公共政策、市场等等)。本研究通过重点论述北非三个地方 (摩洛哥、突尼斯和阿尔及利亚) 地下水抽取用于灌溉农业的评价提供了一些可能的答案。努力了解影响灌溉实践的不同特点,采用了一种合适的、面向使用者的方法来监测地下水的抽取量。通过了解农民所掌握的情况,确定了每个地方影响区域地下水抽取的不同关键因素及过去的演化过程。诸如农民使用土地和地下水或者公共基础设施的发展等因素对于解译井目录结果、评价区域地下水抽取量及其将来趋势至关重要。这将使人们谨慎看待可能过于简单化的、文献中记载的井的数量。ResumoOs recursos hídricos subterrâneos em áreas semiáridas e, especialmente, no Mediterrâneo, enfrentam uma demanda crescente pela agricultura irrigada e, em menor escala, pelos usos domésticos. Consequentemente, as reservas de águas subterrâneas são afetadas e o rebaixamento do lençol freático é amplamente observado. Isso acarreta fortes restrições no acesso à água subterrânea para os agricultores, enquanto os gestores preocupam-se com a evolução futura dos recursos hídricos. Um problema comum para a construção de planos adequados de manejo de águas subterrâneas é a dificuldade em avaliar as retiradas individuais de águas subterrâneas em escala regional. Prever tendências futuras dessas retiradas de águas subterrâneas é ainda mais desafiador. A questão básica é como avaliar as variáveis do balanço hídrico e sua evolução quando estão profundamente ligadas às atividades humanas, impulsionadas por inúmeros fatores (acesso a recursos naturais, políticas públicas, mercado, etc.). Este estudo fornece algumas possíveis respostas, concentrando-se na avaliação de retiradas de águas subterrâneas para a agricultura irrigada em três locais no norte da África (Marrocos, Tunísia e Argélia). Esforços foram feitos para compreender as diferentes características que influenciam as práticas de irrigação, e uma metodologia adaptativa orientada ao usuário foi usada para monitorar as retiradas das águas subterrâneas. Para cada sítio, foram identificados diferentes fatores-chave que afetam a captação de águas subterrâneas regionais e a sua evolução anterior, envolvendo o conhecimento dos agricultores. Fatores como o acesso dos agricultores às terras e às águas subterrâneas ou desenvolvimento de infraestruturas públicas (rede de distribuição elétrica) são cruciais para decodificar os resultados dos inventários de poços e avaliar a captação de águas subterrâneas regionais e a sua tendência futura. Isto leva a olhar com cautela para o número de poços citados na literatura, o que poderia ser simplificado demais.

Drainage Design in the Gharb Plain in Morocco

The Gharb plain in Morocco faces both problems of excesswinter rainfall and salinity hazards due to a shallow,permanent and saline groundwater. A large area of 80.000 hahas been equipped with subsurface drains out of a totalplanned area of 200.000 ha. This system has been designedwithout any local references and has encountered severalmaintenance problems mainly caused by high drain depths.A pilot experiment has been installed to provide drainagedesign criteria appropriate to the local conditions. Mainexperimental results based on water and salinity balance andon groundwater flow are presented in the paper. They show thatin the Gharb plain, drainage systems should be designed fromwinter drainage design criterion. The paper also stresses onthe particular attention to paid to the surface drainage whichremove about 40% of the excess water.

Managing Mediterranean soil resources under global change : expected trends and mitigation strategies

The soils of the Mediterranean Basin are the products of soil processes that have been governed by a unique convergence of highly differentiated natural and anthropogenic drivers. These soils are expected to be dramatically affected by future climate and societal changes. These changes imply that suitable adaptive management strategies for these resources cannot simply be transposed from experiments that are performed in other regions of the world. Following a framework that considers the chain of “drivers-soil process-soil capital-ecosystem services/disservices,” the paper review the research undertaken in the Mediterranean area on three types of Mediterranean soil degradation than can be expected under global change: (i) soil losses due to the increase of drought and torrential rainfall; (ii) soil salinization due the increase of droughts, irrigation, and sea level; and (iii) soil carbon stock depletion with the increase of temperature and droughts. The possible strategies for mitigating each of these degradations have been largely addressed and are still studied in current research projects. They should include changes in agricultural practices, soil water management, and vegetal material. As a pre-requisite for the site-specific adaptations of such mitigation strategies within viable Mediterranean agrosystems, it is highlighted that methodological advances are necessary in integrated assessment of agricultural systems and in finer resolution soil mapping.

Mediterranean land systems under global change: current state and future challenges

The Mediterranean region is one of the areas in the world that is recognized as a hot spot not only for climate change but also more generally for global change. Indeed, the Mediterranean land surfaces and their associated socioecosystems are facing large modifications linked to an increase in drought frequency (Hoerling et al., 2011); to an ever-increasing population, from 370 million in 2000 to probably 560 million in 2030 (Ludwig et al., 2010); and to intense migration to coastal cities (Mediterra, 2008). The future of the Mediterranean socio-ecosystems is therefore questionable. It is even more so because for many years now, their natural resources have been under pressure and became insufficient in many countries when compared to the needs of the populations. The situation is expected to worsen and favor large social tensions, within and between the Mediterranean countries. Water resources are drastically lacking in the southern and eastern Mediterranean countries where 108 million inhabitants are considered water-poor (< 1000 m cap year), and 58% of these live with water shortage (< 500 m cap year) (Blinda and Thivet 2009). Anthropogenic water withdrawals now amount to a large proportion of the annual renewable water resources (Milano et al., 2013). The Mediterranean region also experiences a deficit in agricultural production: for example, in 2003, the Mediterranean basin imported up to 22% of the world imports of cereals but represented only 7% of the world population (Mediterra, 2008). Moreover, arable land is scarce which leads in several countries to the expansion of intensive agriculture, whether irrigated or rainfed, towards marginal land that can degrade when too intensively exploited (Mediterra, 2008). This is amplified by the fast urbanization of coastal areas where soil artificialization decreases arable land. Consequently, the present trends towards an intense exploitation of the natural resources of the Mediterranean ecosystems are likely to put strong pressures on their hydrological and biogeochemical cycles (e.g., carbon, salts, trace elements, xenobiotics) and exacerbate their degradation. Seeking sustainable development in the Mediterranean region requires improving deeply our understanding of the processes of degradation, resilience, and restoration of the variety of Mediterranean socio-ecosystems. In 2010, the international research initiative Mistrals (http://www.mistrals-home.org/) was launched for studying over a decade the environmental behavior of the whole Mediterranean basin submitted to global change. In the framework of Mistrals, several sub-initiatives took place. One of them, SICMED (Surfaces and Interfaces of the Continental MEDiterranean, www.sicmed.net) was supported by the following French research institutes: CNRS-INSU, INRA, IRD, and IRSTEA. It aimed at developing a regional cooperation process for long-term * Marc Voltz marc.voltz@inra.fr