Dew, fog, and rain as supplementary sources of water in south-western Morocco

International audienceThis study reports on one year (May 1, 2007 - April 30, 2008) of dew, fog and rain measurements carried out in the dryland area of Mirleft, Morocco in order to be used as alternative or supplemental sources of water. Four standard dew condensers and a passive fog net collector of 1 m² surfaces were used. Meteorological data were collected. 178 dew events (18.85 mm), 31 rain events (48.65 mm) and 7 significant fog episodes (1.41 mm) occurred, corresponding to almost 40% of the yearly rain contribution (48.65 mm, 31 events). Chemical and biological analyses were carried out. Dew and rain pH were neutral (close to 7) and the total mineralization was considerable (dew: 560 mg/L; rain: 230 mg/L). Ca²+, K+, SO42- and NO3- are found of continental origin; Cl-, Na+ and Mg2+ are of sea origin. The ions concentration agrees with the World Health Organization recommendations for potable water. The biological analysis shows harmless vegetal spores and little contamination by animal/human bacteria. A cost analysis shows that, with little investment, the population of the arid and semi-arid coastal areas of south-western north Africa could make dew water an interesting supplementary alternative water resource

The song of the dunes as a self-synchronized instrument

Since Marco Polo (1) it has been known that some sand dunes have the peculiar ability of emitting a loud sound with a well defined frequency, sometimes for several minutes. The origin of this sustained sound has remained mysterious, partly because of its rarity in nature (2). It has been recognized that the sound is not due to the air flow around the dunes but to the motion of an avalanche (3), and not to an acoustic excitation of the grains but to their relative motion (4-7). By comparing several singing dunes and two controlled experiments, one in the laboratory and one in the field, we here demonstrate that the frequency of the sound is the frequency of the relative motion of the sand grains. The sound is produced because some moving grains synchronize their motions. The existence of a velocity threshold in both experiments further shows that this synchronization comes from an acoustic resonance within the flowing layer: if the layer is large enough it creates a resonance cavity in which grains self-synchronize.Comment: minor changes, essentially more references

El patrimonio geológico de Marruecos: una potencialidad para el desarrollo de un turismo de salud, como factor de lucha contra la pobreza

The whole Moroccan territory conceals a rich essentially thermal and mineral geological heritage. The exploitation of this national heritage to therapeutic ends can play an important economic and social role by the generation of jobs, especially in the arid and of the Sahara zones that endure the drought, the desertification and the emigration of the farming youngsters. It is in the setting of the call of the Chief of Staff of the united Nations inviting, in the declaration of the Millennium, the nations to contribute important way to the struggle against poverty and the extreme poverty, that we proposed, for these resource less surroundings, the tourism of health like an alternative of development associating the struggle against poverty and the lasting tourism. Our article also appears in the setting of the National Initiative for the Human Development (NIHD), placing the Moroccan citizen as finality of the develop-ment strategies and first factor and strength of this developmen

El patrimonio geológico de Marruecos: una potencialidad para el desarrollo de un turismo de salud, como factor de lucha contra la pobreza

El conjunto del territorio marroquí encierra un rico patrimonio geológico esencialmente térmico y mineral. La explotación de este patrimonio nacional con fines terapéuticos puede desempeñar un papel económico y social importante para la creación de empleo, sobre todo en las zonas áridas y saharianas que sufren la sequía, la desertificación y la emigración de los jóvenes que habitan en zonas rurales. En el marco la Declaración del Milenio de las Naciones Unidas invitando a las naciones del mundo a contribuir de manera prioritaria en la lucha contra la pobreza y la extrema pobreza, se inserta nuestra propuesta, para los sectores más desprovistos, de un turismo de salud como la clave para asociar la lucha contra la pobreza y el turismo sostenible, sin desvirtuar el patrimonio natural ni condenarlo a la desaparición. Nuestro artículo se inscribe asimismo en el marco de la Iniciativa Nacional para el Desarrollo Humano (INDH) que sitúa el ciudadano como objetivo de las estrategias de desarrollo y factor prioritario del mismo

Evolution of sand encroachment using supervised classification of Landsat data during the period 1987–2011 in a part of Laâyoune-Tarfaya basin of Morocco

The study anticipated to understand sand encroachment evolution through analysis of sand contribution across space and time using remote sensing in Laâyoune-Tarfaya basin, Morocco, over the period from 1987 to 2011. The assessment based on supervised classifications of Landsat imagery orthorectified data, using Maximum Likelihood (ML), Minimum Distance (MD) and Support Vector Machine (SVM) classifiers. In order to ameliorate the information, principal components analysis (PCA) and co-occurrence measurement algorithm were used for choosing bands and data transformation. Images differencing was applied on image pairs derived from classification to analyze sand encroachment evolution. All classifiers present enhanced performances, and revealed that area covered by sand was increased by 7%, 4.66% and 4.59% for ML, MD and SVM, respectively. Consequently, images differencing results confirmed that sand material increasing arise not only from coastal area contribution but also mostly from erosion of complicated sand dunes exist in the middle part of the studied area. Evaluating of the presented phenomenon dimensions and its consequences are extremely important to increase the local authorities awareness and mainly for avoiding or minimizing the consequences of the future sand dunes threats