Kerrou, Jaouhar

2010, Kerrou, Jaouhar, Renard, Philippe, Lecca, Giuditta, Tarhouni, Jamila

L'aquifère de Korba, situé au nord de la Tunisie, est gravement touché par une salinisation du à l'intrusion marine. En 2000, l'aquifère a été exploité par plus de 9000 puits. Le problème, c'est qu'il n'y a pas d'information précise concernant les débits de pompage, leur répartition dans l'espace ainsi que leur évolution dans le temps. Dans cette étude, un modèle géostatistique des débits d'exploitation a été construit en se basant sur une régression multilinéaire combinant des données directes incomplètes ainsi que des données secondaires exhaustives. Les impacts de l'incertitude associée à la distribution spatiale des débits de pompage sur l'intrusion marine ont été évalués en utilisant un modèle tridimensionnel d'écoulement et de transport à densité variable. Pour contourner les difficultés liées à de longs temps de calcul, nécessaires pour résoudre des problèmes en régime transitoire, les simulations ont été réalisées en parallèle sur une grille informatique de calcul mise à disposition par le projet “Enabling Grid for E-Science in Europe”. Les résultats des simulations de Monte Carlo ont montré que 8.3% de la surface de l'aquifère est affectée par l'incertitude liée aux données d'entrée., The Korba aquifer, located in the north of Tunisia, suffers heavily from salinization due to seawater intrusion. In 2000, the aquifer was exploited from more than 9000 wells. The problem is that no precise information was recorded concerning the current extraction rates, their spatial distribution, or their evolution in time. In this study, a geostatistical model of the exploitation rates was constructed based on a multi-linear regression model combining incomplete direct data and exhaustive secondary information. The impacts of the uncertainty on the spatial distribution of the pumping rates on seawater intrusion were evaluated using a 3-D density-dependent groundwater model. To circumvent the large amount of computing time required to run transient models, the simulations were run in a parallel fashion on the Grid infrastructure provided by the Enabling Grid for E-Science in Europe project. Monte Carlo simulations results showed that 8.3% of the aquifer area is affected by input uncertainty.

2010, Kerrou, Jaouhar, Renard, Philippe, Tarhouni, Jamila

The Korba aquifer is located in the east of the Cape Bon peninsula in Tunisia. A large groundwater depression has been created in the central part of the aquifer since the 1980s, due to intense groundwater pumping for irrigation. The data collected show that the situation continues to deteriorate. Consequently, seawater is continuing to invade a large part of the aquifer. To better understand the situation and try to forecast its evolution, a three-dimensional (3D) transient density-dependent groundwater model has been developed. The model building process was difficult because of data required on groundwater discharge from thousands of unmonitored private wells. To circumvent that difficulty, indirect exhaustive information including remote sensing data and the physical parameters of the aquifer have been used in a multi-linear regression framework. The resulting 3D model shows that the aquifer is over-exploited. It also shows that after 50 years of exploitation, the time needed to turn back to the natural situation would be about 150 years if the authorities would ban all exploitation now. Such an asymmetry in the time scales required to contaminate or remediate an aquifer is an important characteristic of coastal aquifers that must be taken into account in their management.