The HMS(hydrologic modeling system) model is one of the most used model thanks to its capabilities and panoply of modelling formalisms. However, more effort should be done to facilitate the estimation of initial values of parameters of the HMS model. In this article, we propose a comprehensive approach to estimate initial values of the parameters of the HMS formalisms. The formalisms concerned are the five loss methods, the simple canopy method and the simple surface method. The approach use data of the African soil grid 250m data for parameters estimated based on soil properties, a supervised classified ETM+ satellite image for parameters needing land use characteristics and the daily discharge for parameter demanding stream flow recession analysis. The basin of Bin El Ouidane was chosen as a case of study, in order to assimilate the estimation approach and the data utilization.

Résumé -La sécheresse a toujours été présente dans l'histoire du Maroc, elle s'est imposée avec force ces dernières décennies en tant qu'élément structurel du climat du pays. Le Maroc vit actuellement l'épisode sec le plus long de son histoire contemporaine, caractérisé par une diminution des précipitations et une tendance nette à la hausse des températures. La caractérisation de la sécheresse climatique au cours de la période 1961-2004 a montré une augmentation significative de la fréquence des sécheresses, de leur sévérité et de leur champ de couverture spatiale. Cette dynamique de sécheresse s'accompagne d'un réchauffement important lié au changement climatique planétaire, qui rend ces années sèches de plus en plus difficiles pour différents secteurs socio-économiques du pays. Mots clés -sécheresse, réchauffement, précipitation, température, MarocAbstract -Drought was always present in Morocco's history. Its importance as a structural element of the country's climate increased these last decades. Morocco lives the longest dry episode of its contemporary history, characterized by a reduction of the precipitations and a tendency to the rise in temperatures. The characterization of the climatic drought during the period 1961-2004 showed an increase in the droughts frequency, their severity and their spatial distribution. This drought dynamics is associated to an important warming up related to the global climate change that makes these dry episodes more and more difficult for different socioeconomic sectors.

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All over the world, dam managers are constantly confronted with the siltation of dam reservoirs. This natural phenomenon represents a menace to the safety of the dam; because sediments deposited amplifies the load applied to the dam and shut off the dam’s bottom outlet. It also reduces the usable capacity of the reservoir and degrades the quality of the water stored (pollution, eutrophication, turbidity, etc.). In arid and semi-arid countries like Morocco, de-silting stays the best solution for silted dams. However, when we de-silt dam reservoirs, we produce enormous volumes of mud, which represent potential pollution for the environment and occupy immense terrains. Our research was carried out on the possible uses of these sediments. It has enabled us to develop a valuation guide in Civil Engineering, Agriculture, crafts, and the environment sectors. This guide provides a framework for performing tests and analyses to do on the sediments to compare them with the limit values required by regulations and standards in several economic sectors. The results of these evaluations help us to find the most appropriate uses of the sediments in the sectors mentioned above.

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