La présente étude concerne le barrage Hachef (Barrage nommé 9 Avril 1947), mis en service en 1995, situé dans le Rif Occidental Marocain à environ 30 km au sud de la ville de Tanger et 15 km à l’est de la ville d’Asilah. La retenue du barrage d’une capacité utile de 270 millions de m3 reçoit un apport solide de 609 000 tonnes/an à cause de l’érosion des versants favorisée par le déboisement. Des foyers de pollution sont également identifiés dans les régions limitrophes du barrage. Dans le but de préserver et protéger cette ressource destinée à l’alimentation en eau potable de la population des régions voisines, il s’est avéré nécessaire de mettre en place des périmètres de protection. Ceci entraîne également une plus grande rentabilité des investissements et infrastructures réalisés. Dans ce travail, une solution informatisée pour la délimitation des périmètres de protection a été conçue et réalisée. Ainsi, un modèle d’analyse spatiale par le SIG basé sur l’évaluation de la vulnérabilité à la contamination de la ressource a été élaboré. Toutes les données disponibles, aussi bien celles issues de la télédétection que celles du terrain, ont été modélisées et intégrées au sein d’une base de données géographique gérée par un SIG. Dans cette expertise, les différents aspects de la problématique concernant la sauvegarde de la ressource en eau ont été cernés et les besoins des gestionnaires ont été recensés. L’utilisation de cette méthode a permis de délimiter les trois zones de protection autour de la retenue du barrage (zones de protection immédiate, rapprochée et éloignée).Due to the degradation of the quality of Moroccan water resources, it is necessary to set up mechanisms and actions to ensure their conservation and protection. The creation of protection zones is one of the more effective means for establishing this protection. The study region involved the Hachef dam, operating since 1995 and located in the Moroccan Occidental Rif, approximately 30 km south of Tangiers City and 15 km east of Asilah City. The watershed area is 220 km2 with an annual average precipitation of 900 mm. The useful capacity of the dam is 270 million m3. By storing 90 million m3/year in normal years, this dam supplies a water supplement to the existing resources, covering drinking water requirements and irrigation for the region located between Tangiers and Asilah beyond the year 2015.In order to classify the importance of protection from pollution, the watershed was divided into three zones (zones I, II and III), as defined by their distance from the resource to be protected. In the immediate protection zone (zone I), it is necessary to assure protection of the dam against water pollution. The dimension of this zone should allow for appropriate intervention in the event of an accident and also allow for planting of a forest or a zone of protective vegetation. In the next protection zone (zone II), one should assure protection against pollution and other anthropogenic stressors that could threaten the harnessed waters. In zone III, locat...
Water erosion, considered as a natural process accelerated by man, is the main cause of the degradation of our agropedological heritage as well as the deterioration of water quality that it entails. Topographical and climatological factors associated with high population growth make Morocco a favorable area for erosion phenomena (water erosion, wind erosion, etc).The present study calls upon the use of remote sensing and a geographical information system (GIS) for quantifying annual soil losses in conjunction with the use of the universal soil loss equation (USLE), the quanity of sediments that will be delivered to the drainage network as well as the erosional potential of the Oued Aricha watershed (Province of Settat, Morocco).As expected, the highest soil loss rates were recorded in regions of bare soils. We also noted that important soil losses (more than 20 t/ha/yr) can be related to only one third of the study area (34.94%); the soil loss map also shows that these areas are mostly located along river and stream banks. In areas where the quantity of sediments delivered to the drainage network is as large as that lost at the origin, we can conclude that the topography and the nature of the soil are favorable to the erosion of materials and their delivery to the drainage network.This study has demonstrated that remote sensing, used in conjunction with other data sources provides remarkable and unique information for the determination of soil erosion and susceptibility to erosion, at scales varying from 1:50 000 to 1:200 000.
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...
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