Le présent travail a pour objectif la modélisation hydrodynamique de la nappe Quaternaire de Figuig ; généralement la nappe circule dans des alluvions limoneuses et des calcaires travertineux du Quaternaire avec un substratum imperméable constitué des marnes du Jurassique. La zone d’étude est caractérisée par un climat désertique. La modélisation hydrogéologique a été mise en œuvre par le logiciel MODFLOW. La nappe a été simulée en régime permanent et transitoire ; elle résout l’équation gouvernante de l’écoulement des eaux souterraines en milieux poreux continus et elle calcule la charge hydraulique par simulation des éléments comme : drain, puits, oued, etc. Le modèle numérique ainsi élaboré a permis d’estimer le bilan des aquifères des palmeraies de Figuig et de la plaine de Tisserfine-El Arja dans les deux cas : les conditions actuelles et le scénario de gestion simulant l’élimination des apports des barrages de Sfissif et de Rkiza, par l’oued Tisserfine jusqu’à l’oued Zouzfana.   The current study aims at providing a hydrodynamic model of the Quaternary water aquifer in Figuig; the water aquifer generally flows in a silty alluvial soil and travertine limestone of the Quaternary with an impermeable substratum of the Jurassic marl. The area of the study is characterised by a desert climate. The hydrogeological modelling was carried out using the MODFLOW software. The groundwater was simulated in permanent and transient regime; it solves the governing equation of groundwater flow in continuous porous media and calculates the hydraulic load by simulating elements such as: drain, well, river... Therefore, the digital model developed allowed us to estimate the aquifer balance of Figuig palm groves and Tisserfine-El Arja plain in the two cases: the current conditions and the management scenario simulating the elimination of the inflows from the Sfissif and Rkiza dams, through the Tisserfine wadi to the Zouzfana wadi.

The Fez-Meknes basin consists geomorphologically of the Meknes plateau to the west and the saïss plain to the east, separated by the Ain Taoujtat flexure. It is characterized by a semi-arid climate. Hydrogeologically, the basin contains two important aquifer reservoirs, a free and a captive water table. The first one circulates in the Plio-Villafranchian formations, while the second one is deep in the dolomitic limestone of the Lias. These two aquifers communicate with each other in some places, either directly through flexures and faults or indirectly through upward drainage. They are the main sources of drinking water and irrigation. These two aquifers have been overexploited due to successive years of drought and agricultural use. Thus, this work aims to monitor the piezometric level of the free water table through several field trips, technical data sheets of the drillings, geological and topographical maps. The analysis of rainfall data in the stations located around the piezometers in the study area allowed to distinguish a low water period (June, July, August and September) and a high-water period (March, April and May). The piezometric maps were made on the basis of the comparison between kriging and TIN during the low and high-water period. The TIN method has been recommended as the most reliable one.

The present study aims at mapping areas vulnerable to water erosion based on the Priority Activity Program/ Regional Activity Center (PAP/CAR) model guidelines, geomatics, remote sensing, and GIS in the Errachidia-Boudenib Cretaceous basin. This basin is located in south-eastern Morocco and covers an area of 13 000 km 2 , the basin is 320 km long and 75 km wide. The method of estimating water erosion is composed of three phases; a predictive phase consisting of a mapping of predisposing factors such as slope, substrate, and/or soils and vegetation cover, a descriptive phase based on the mapping of actual erosion, and an integration phase to arrive at the identification and evaluation of the erosion risk. The mapping of areas vulnerable to water erosion indicates that 70% of the studied basin has low erodibility and 22% is notable, while only 8% has high to very high erodibility. The areas most affected by degradation are located at the end of the basin and correspond to lands with steep slopes (>35%). Consequently, this study has allowed us to locate certain sectors and roads that may be affected by this type of erosion, namely the mountainous areas of the High Atlas and roads numbered R13, R601, R 703, and P7106.

This paper aims to determine the hydrogeochemical characteristics of the Fez-Meknes free water table thought the monitoring of the physicochemical analyses of nine samples during the year of 2013, 2016, and 2019. This water table, which circulates in the plio-quaternary formations, is generally supplied by rainfall infiltration, irrigation water returns and also the lateral inflow of the unconfined liasic water table of the Middle Atlas Tabular. Analyses were performed for electrical conductivity (EC), potential hydrogen (pH), temperature and major elements: Cl-, NO3-, SO42-, Na+, Mg2+, Ca2+, HCO3⁻, K+. The results of the projection of the samples on the Piper diagram for the three companies showed a hydrochemical carbonate, calcic and magnesian facies for the majority of the samples with the exception of samples 1161/15 and 352/21 for the year 2013. Then, to understand the origin of the mineralization, as well as the processes related to the dissolution of the carbonate country rock, a principal component analysis (PCA) was performed.

In order to model the water flow of the free Quaternary aquifer of the Fez-Meknes basin, it is essential to determine the precise geometric limits of the aquifer. Indeed, the characterization and representation of the underground structure of the Miocene marl top which forms the aquiclude of the aquifer, constitutes the fundamental step to study and understand its influence on the groundwater flow. This study is facilitated by the available data, which allow to represent the underground formations on isohypses maps. The data base is formed by reconnaissance drillings, and the extraction of marl altitudes from previous geological works. During this work the generation of the marl top elevation map was based on the test of four interpolation methods, which correspond to : Kriging, IDW method, Natural Neighbors, and Topo to Raster, in order to choose the most reliable and best suited to the study area. On the one hand, the calculation of the conformity index between the values measured in the field and the estimated values for each method was successively (0.9796, 0.9848, 0.9814, 0.9842). On the other hand the values of the root mean square error (RMSE) were successively (13.59, 7.42, 21.27, 14.01). The comparison of these results allowed us to choose the IDW interpolation as the most reliable and suitable to interpolate the top of the aquiclude of the free water table of the Fez Meknes basin with a compliance index the highest and a RMSE the lowest compared to other methods.