MODÉLISATION NUMERIQUE DE L’EFFET DES CHANGEMENTS CLIMATIQUES SUR LA NAPPE DE BERRECHID (MAROC)

Morocco takes part of the arid countries where groundwater resources play a vital role for their socio-economic development. The important increase in the water demand for various uses, coupled with the negative effects of the climate changes stresses increasly these groundwater reserves and weakens them. At the river watershed Bouregreg, both the quantity and the quality of groundwater are strongly decreased during last decades, especially at the Berrechid aquifer where the level of water, decreases continually in the piezometers during the period: 1980-2008, reaching 20 m in some places. The objective of this study is to analyze the impacts related to both the climate changes and the increase of water demand on the aquifer hydrodynamic to improve management and planning groundwater resources. Thus, a numerical model to simulate the aquifer hydrodynamics is proposed. It is based on MODFLOW, using GMS interface. The analysis of the impact of the climate changes on groundwater resources mobilized is based on Intergovernmental Panel one Climate Changes (IPCC) approach in terms of scenarios. The constraints imposed to the numerical model were based on three scenarios of IPCC, taking account of the aquifer’s recharge variation. The results show the continuing trend of declining groundwater levels with a variation between 1m and 25m

MODÉLISATION NUMERIQUE DE L’EFFET DES CHANGEMENTS CLIMATIQUES SUR LA NAPPE DE BERRECHID (MAROC)

Morocco takes part of the arid countries where groundwater resources play a vital role for their socio-economic development. The important increase in the water demand for various uses, coupled with the negative effects of the climate changes stresses increasly these groundwater reserves and weakens them. At the river watershed Bouregreg, both the quantity and the quality of groundwater are strongly decreased during last decades, especially at the Berrechid aquifer where the level of water, decreases continually in the piezometers during the period: 1980-2008, reaching 20 m in some places. The objective of this study is to analyze the impacts related to both the climate changes and the increase of water demand on the aquifer hydrodynamic to improve management and planning groundwater resources. Thus, a numerical model to simulate the aquifer hydrodynamics is proposed. It is based on MODFLOW, using GMS interface. The analysis of the impact of the climate changes on groundwater resources mobilized is based on Intergovernmental Panel one Climate Changes (IPCC) approach in terms of scenarios. The constraints imposed to the numerical model were based on three scenarios of IPCC, taking account of the aquifer’s recharge variation. The results show the continuing trend of declining groundwater levels with a variation between 1m and 25m

IMPACT DE LA FRACTURATION SUR L’ARCHITECTURE DU RESEAU HYDROGRAPHIQUE (CAS DE LA REGION DE SMAALA, MAROC CENTRAL HERCYNIEN) APPORT DU SIG ET DE LA TELEDETECTION

In the Smaala area, Paleozoic rocks crop out and are structured by the Hercynian orogeny. The hydrographic network is dense and displays various flow directions. It consists of temporary streams that eventually lead to the Grou river. Analysis of the Landsat TM satellite image can extract lineament network. The majority of these lineaments coincide with geological fractures identified on the field. Their distribution is organized around four major directions: NE-SW, N-S, NW-SE and E-W. The comparison of the statistics of the hydrographic network with those of lineaments shows that the majority of rivers are affected by geological structures, especially the fracturing. The topography of the area also has a secondary impact on the water circulation, by the presence of slopes generally oriented North-West and North

IMPACT DE LA FRACTURATION SUR L’ARCHITECTURE DU RESEAU HYDROGRAPHIQUE (CAS DE LA REGION DE SMAALA, MAROC CENTRAL HERCYNIEN) APPORT DU SIG ET DE LA TELEDETECTION

In the Smaala area, Paleozoic rocks crop out and are structured by the Hercynian orogeny. The hydrographic network is dense and displays various flow directions. It consists of temporary streams that eventually lead to the Grou river. Analysis of the Landsat TM satellite image can extract lineament network. The majority of these lineaments coincide with geological fractures identified on the field. Their distribution is organized around four major directions: NE-SW, N-S, NW-SE and E-W. The comparison of the statistics of the hydrographic network with those of lineaments shows that the majority of rivers are affected by geological structures, especially the fracturing. The topography of the area also has a secondary impact on the water circulation, by the presence of slopes generally oriented North-West and North

Applied Latin Hypercube stochastic method to quantify the uncertainty in groundwater equation model simulations

It is accepted that digital models simplify the physical reality that is the object of the modeling. Hydrodynamic modeling is an approach with high uncertainties in this context. Indeed, the deterministic modeling approach assumes the existence of a functional relationship between the observed variables. The variables are observed by a series of measurements riddled with errors. Because of this, there is always a significant amount of uncertainty associated with a hydrogeological model. This uncertainty can be associated with the conceptual model or with the data and parameters associated with the different components of the model. Some model parameters such as hydraulic conductivity and recharge are particularly susceptible to uncertainty. Stochastic modeling of the hydrodynamics of a groundwater reservoir is an adequate response to allow us to take a step back on the significance of the results. The study is based on the development of a direct problem-solving model which represents the best estimate of the real hydrodynamic system. This model is used to make predictions. With a stochastic approach, a set of models is constructed where each model, as a whole, is considered to be equally likely. Each model is then used to make the prediction or simulate a given scenario. The MODFLOW-STOCHASTIC-GMS code allows us to do randomization simulations (Latin Hypercube method) and with parameter indicators

Groundwater flow equation, overview, derivation, and solution

Darcy’s law is the basic law of flow, and it produces a partial differential equation is similar to the heat transfer equation when coupled with an equation of continuity that explains the conservation of fluid mass during flow through a porous media. This article, titled the groundwater flow equation, covers the derivation of the groundwater flow equations in both the steady and transient states. We look at some of the most common approaches and methods for developing analytical or numerical solutions. The flaws and limits of these solutions in reproducing the behavior of water flow on the aquifer are also discussed in the article

A study of water infiltration basin and clogging using column experiments

The clogging of infiltration basins is the main problem affecting the proper functioning of groundwater artificial recharge systems. In this study, several parameters have been varied to understand their impacts on water infiltration. The experimental results show that the effect of initial humidity is significant for less porous material such as silty soil (Hamri) and sand. The air bubbles are also an important factor to take into consideration since when trapped within porous structures, it forms a barrier for the displacement of water infiltration. The accumulation of suspended particles in stormwater can contribute to clogging by creating a light layer due to the finest particles, which remain in suspension for a long time. Finally, for the tested materials and experimental conditions, we observed that a combination of a silty soil and sand layer in the design of infiltration basins was more practical than a combination of sand and gravel. The latter, despite its high porosity, could release very fine particles; which would create a cement layer of clogging when deposited at the interface. This layer is an obstacle for water infiltration, thus rendering the device thus constructed unsuitably for groundwater recharge, by reducing its life

Programmation de la solution de Glover en deux dimensions pour évaluer la recharge artificielle des aquifères

Pour estimer l'importance du monticule hydraulique formé sous un dispositif d'infiltration lors d'une opération de recharge artificielle, une série de modèles analytiques ont étés développés [Baumann, 1952 ; Glover, 1960 ; Hantush, 1967 ; Hunt, 1971 ; Rao et Sarma, 1981], et autres. Dans ce travail, la solution apportée par le modèle de Glover a été programmée et analysée pour le cas d'un bassin d'infiltration rectangulaire avec une injection continue. Nous avons développé un code numérique en langage C++ capable de décrire la réponse de la nappe phréatique vis-à-vis d'une opération de recharge artificielle. Trois solutions analytiques ont été utilisées et comparées à des données expérimentales de Bianchi et al. [1975]. Les solutions supposent un aquifère homogène, isotrope, non confiné avec recharge constante, surface piézométrique de la nappe phréatique initialement horizontale. La hauteur du monticule générée par la recharge doit être également faible par rapport à l'épaisseur initiale saturée de l'aquifère. Les résultats des simulations à l'aide de ce code numérique montrent que la solution de Glover donne des estimations raisonnables en comparaison avec les données expérimentales de Bianchi et al. [1975] et celles du modèle de Hantush. Ce modèle peut donc être utilisé pour une analyse préliminaire dans la gestion des bassins d'infiltration des eaux de surface. Cette solution a été utilisée pour réaliser des simulations de recharge artificielle de la nappe de Charf Al Akab au NW du Maroc. Il faut cependant souligner que, malgré les estimations raisonnables données par la solution analytique de Glover, celle-ci reste limitée et souffre de beaucoup d'hypothèses comme l'homogénéité du sol, un taux d'infiltration constant et un milieu isotrope, ce qui n'est pas toujours le cas en réalité ; d'où le recours aujourd'hui à l'utilisation des modèles numériques qui semblent plus adaptés à des situations réelles souvent complexes