Bilan hydrologique et envasement du barrage Saboun (Maroc)

La présente étude s'inscrit dans le cadre d'un programme de recherche sur la gestion des lacs et barrages collinaires en zone méditerranéenne HYDROMED. Elle a pour objectif le suivi hydrologique et la sédimentation du barrage collinaire Saboun, situé dans la zone de Tanger au Nord-Ouest du Maroc. Un dispositif hydro-pluviométrique automatique a été installé à ce sujet depuis novembre1997. Il a permis le suivi du bilan en eau de la retenue et l'analyse de son fonctionnement hydrologique. Parallèlement, une étude de la bathymétrie par sondage ponctuel a montré que le taux de sédimentation est de l'ordre de 2% par an. Cette perte en eau de la capacité totale de la retenue est une conséquence directe d'une forte dégradation des sols du bassin versant estimée à 115 T/ha/an.It is proposed that many Mediterranean countries could make better use of their water resources by constructing small hill reservoirs. Since 1980, Morocco has built more than 158 small dams in order to meet the requirements of rural population water use. Due to both environmental degradation and bad management, these small infrastructures are now in a critical situation. Furthermore, pollution and siltation, resulting in a deterioration of water quality and a reduction of water capacity, are problems at these sites.The present study is part of the HYDROMED research program on the hydrological balance of small dams in the Mediterranean area. Its objective is the monitoring of hydrological balance and siltation of a small dam, Saboun, located in Tangier in Northwest Morocco. A remote hydrological station was installed in November 1997. This station allowed the examination of the dam water balance and analyses of its hydrological function.The analyses of water balance demonstrated that the volume of water stored in the Saboun reservoir increased rapidly in November 1997, and was then followed by a progressive decrease. The load factor varied from 1.9 in 1997/98 to approximately 2 times the current capacity of reservoir, to only 0.3 in the following year 1998/99. These results show that even for a short hydrological period (2 years), the hydrological balance of the Saboun reservoir varied greatly as a result of the irregularity of its hydrological parameters. The essential reasons for this variability were the rainfall characteristics that control the runoff from the watershed and bad management practices.In addition, a bathymetric survey was carried out by a punctual method to estimate the rate of dam siltation and sedimentation from the watershed. The results of this control demonstrated that the dam siltation rate was about 2 % per year. This loss of total water retention capacity of the dam is the consequence of high specific soil degradation of the watershed. The rate of sediment delivered from watershed and deposited in the reservoir was estimated at 37 T/ha/year. The total soil erosion for watershed was estimated at 115 T/ha/year by integrating both the sediment evacuated at the time of dam overflow and the sediment deposited in stream flow. This erosion, which comes essentially from cultivated soil (95 % of the watershed surface), may have serious effects on the hydrological balance of the dam, particularly by reducing the reservoir capacity of the dam, and on the reservoir water quality

Les formations fluviatiles quaternaires de la plaine de Doukkala (Méséta Occidentale Marocaine). Sédimentologie et nouvelles données chronostratigraphiques

The Quaternary fluvial formations of the Doukkala plain are, until now, slightly studied. Our study has allowed to precise that the fluvial terraces of the oued "the Ourn Rbia oued", are clearly distinguished from the secondary oueds terraces by the dynamic deposit of the alluvial materials. Moreover, the mammal fossils recolted from some of these terraces allow to review the ages attributed by Gigout (1951)

Risques géologiques et activité sismique dans la région d'Al Hoceima (Maroc) : Approche de la quantification des facteurs responsables du déclenchement des instabilités de terrain Geological hazards and seismic activity within the area of Al Hoceima (Morocco): Approach of quantifying factors responsible for the triggering of the ground instabilities

International audienceCe travail présente une étude des risques géologiques liés à l'activité sismique de la région d'Al Hoceima, Maroc. Cette étude a nécessité l'identification des modifications récentes enregistrées dans les formations géologiques, conséquentes de la crise sismique qu'a connue la région en 1994. L'analyse de ces phénomènes a permis de mettre en évidence les liens entre la sismicité et les instabilités de terrain. Un essai de quantification des facteurs responsables du déclenchement de ces instabilités a conduit à suggérer que la pente ainsi que la sismicité constituent les facteurs capitaux dans l'occurrence des mouvements de terrain. This work presents a study of the geological hazards caused by seismic activity within Al Hoceima region, Morocco. This study required the identification of recent geological modifications caused by the seismic crisis of 1994. The analysis undertaken revealed the existence of a good correlation between seismicity and the geological field data. Furthermore, an attempt of quantifying the triggering factors of land instabilities caused us to suggest that the slope and seismicity are the main factors in the studied area

Précisions sur la chronostratigraphie des formations litttorales quaternaires au Nord-Est de Rabat (Maroc). Apport de la thermoluminescence

Chronostratigraphie precisions on the Quaternary littoral formations to the NE of Rabat (Morocco). Contribution from the thermoluminescence. The geomorphological disposition and sedimentological characteristics of deposits have permit to retrace globa-ly the conditions to sit littoral quaternary formations of North-East of Rabat. One stratigraphy based on paleontological and prehistorial archeological coins have been realased. The method of dating by thermoluminescence confirm and specify this stratigraphy.La disposition géomorphologique et les caractéristiques sédimentologiques des dépôts ont permis de retracer globalement les conditions de mise en place des formations littorales quaternaires du Nord-Est de Rabat. Une stratigraphie basée sur des pièces paléontologiques et archéologiques préhistoriques a été établie. La méthode de datation par thermoluminescence confirme et précise cette stratigraphie.Aberkan M. Précisions sur la chronostratigraphie des formations litttorales quaternaires au Nord-Est de Rabat (Maroc). Apport de la thermoluminescence. In: Géologie Méditerranéenne. Tome 27, numéro 1-2, 2000. pp. 27-31

Contribution à l'étude géomorphologique et sédimentologique du Quaternaire de la vallée de l'Oum Rbia (Méséta côtière atlantique -Maroc)

Quaternary geomorphology and sedimentology of the Oum Rbia valley (coastal Meseta, Morocco). The Oued Oum Rbia valley shows a varying morphology in different parts of the Doukkala basin. The geomorphology and its evolution (in space and time) is dependent on a number of factors, such as topography, lithology, tectonics, climate, eustasy and human activity. The sedimentological characteristics of the Early Quaternary fluvial terraces (conglomeratic deposits) differ from those of the Late Quaternary (silly deposits). With regard to the other factors, the nature of the detritic discharge is controlled by the dynamics, by neotectonics and the climatic context.Dans le bassin des Doukkala, la vallée de l'Oued Oum Rbia présente une morphologie variable selon les secteurs de ce bassin. L'aspect géomorphologique de cette vallée et son évolution, tant dans l'espace que dans le temps, sont le résultat de plusieurs facteurs : topographie, lithologie, tectonique, climat, sans négliger l'action anthropique. Les caractéristiques sédimentologiques des terrasses fluviatiles du Quaternaire ancien différent de celles du Quaternaire récent. La nature des apports détritiques aurait, sans doute, été contrôlée en plus de la dynamique sédimentaire, par la néotectonique et le contexte climatique.Ouadia Mohamed, Aberkan M. Contribution à l'étude géomorphologique et sédimentologique du Quaternaire de la vallée de l'Oum Rbia (Méséta côtière atlantique -Maroc). In: Géologie Méditerranéenne. Tome 23, numéro 2, 1996. pp. 89-99

Recent Quaternary fossil mammals of Chrafate and Ez Zarka: the origin of modern fauna in the Northern Rif (Morocco, Northern Africa)

The Northern Rif (Northern Morocco, Northwestern Africa) was characterised in the late Pleistocene and the Holocene by mammal assemblages, which included species with different biogeographic origins. Saharian, Saharo-Mediterranean, Sahelian species as well as some forms adapted to the Mediterranean climatic regime have been recorded. The fossil mammal assemblages recovered from two new localities in karstic infills (Chrafate and Ez Zarka) correspond well with this palaeobiogeographic setting and suggest that this region was a crossroad of palaeoartic and palaeotropical species. The variety observed in the fossil mammal assemblages and in the present mammal fauna resulted from a long period of aridity, which coincided with the late Pleistocene post-glacial stage and was followed by a Holocene humid phase. This palaeoclimatic change resulted from the equator ward shift of the high-pressure cell belt, which allowed the southward shift of less arid Mediterranean climatic zones

Recent Quaternary fossil mammals of Chrafate and Ez Zarka. The origin of modern fauna in the Northern Rif (NW Morocco, Northern Africa)

The Northern Rif (Northern Morocco, Northwestern Africa) was characterised in the late Pleistocene and the Holocene by mammal assemblages, which included species with different biogeographic origins. Saharian, Saharo-Mediterranean, Sahelian species as well as some forms adapted to the Mediterranean climatic regime have been recorded. The fossil mammal assemblages recovered from two new localities in karstic infills (Chrafate and Ez Zarka) correspond well with this palaeobiogeographic setting and suggest that this region was a crossroad of palaeoartic and palaeotropical species. The variety observed in the fossil mammal assemblages and in the present mammal fauna resulted from a long period of aridity, which coincided with the late Pleistocene post-glacial stage and was followed by a Holocene humid phase. This palaeoclimatic change resulted from the equator ward shift of the high-pressure cell belt, which allowed the southward shift of less arid Mediterranean climatic zones

Recent Quaternary fossil mammals of Chrafate and Ez Zarka: the origin of modern fauna in the Northern Rif (Morocco, Northern Africa)

The Northern Rif (Northern Morocco, Northwestern Africa) was characterised in the late Pleistocene and the Holocene by mammal assemblages, which included species with different biogeographic origins. Saharian, Saharo-Mediterranean, Sahelian species as well as some forms adapted to the Mediterranean climatic regime have been recorded. The fossil mammal assemblages recovered from two new localities in karstic infills (Chrafate and Ez Zarka) correspond well with this palaeobiogeographic setting and suggest that this region was a crossroad of palaeoartic and palaeotropical species. The variety observed in the fossil mammal assemblages and in the present mammal fauna resulted from a long period of aridity, which coincided with the late Pleistocene post-glacial stage and was followed by a Holocene humid phase. This palaeoclimatic change resulted from the equator ward shift of the high-pressure cell belt, which allowed the southward shift of less arid Mediterranean climatic zones

Recent Quaternary fossil mammals of Chrafate and Ez Zarka. The origin of modern fauna in the Northern Rif (NW Morocco, Northern Africa)

The Northern Rif (Northern Morocco, Northwestern Africa) was characterised in the late Pleistocene and the Holocene by mammal assemblages, which included species with different biogeographic origins. Saharian, Saharo-Mediterranean, Sahelian species as well as some forms adapted to the Mediterranean climatic regime have been recorded. The fossil mammal assemblages recovered from two new localities in karstic infills (Chrafate and Ez Zarka) correspond well with this palaeobiogeographic setting and suggest that this region was a crossroad of palaeoartic and palaeotropical species. The variety observed in the fossil mammal assemblages and in the present mammal fauna resulted from a long period of aridity, which coincided with the late Pleistocene post-glacial stage and was followed by a Holocene humid phase. This palaeoclimatic change resulted from the equator ward shift of the high-pressure cell belt, which allowed the southward shift of less arid Mediterranean climatic zones

The Pleistocene of Rabat (Morocco): Mollusks, Coastal Environments and Human Behavior

International audienc