Reassessment of the Resources of a Deep Aquifer System under Physical and Chemical Constraints:The Maastrichtian Aquifer
Affiliation(s)
Laboratoire de Mécanique et Modélisation-UFR Sciences de l’Ingénieur, University of Thiès, Thiès, Senegal. Département de Géologie, FST-UCAD, Cheikh Anta Diop University, Dakar, Senegal. Laboratoire de Géologie, IFAN, Cheikh Anta Diop University, Dakar, Senegal. ISRA, Bambey, Senegal.
Laboratoire de Mécanique et Modélisation-UFR Sciences de l’Ingénieur, University of Thiès, Thiès, Senegal. Département de Géologie, FST-UCAD, Cheikh Anta Diop University, Dakar, Senegal. Laboratoire de Géologie, IFAN, Cheikh Anta Diop University, Dakar, Senegal. ISRA, Bambey, Senegal.
ABSTRACT
The deep and confined Maastrichtian aquifer contains considerable groundwater resources. It stretches over nearly 200,000 km2, from the northern part of Mauritania to the South of Guinea Bissau where it becomes shallow. The reservoir is composed mainly of coarse sands and sandstone interbedded with some clay units. The aquifer provides 40% of the total drinking water extracted from the different aquifers and nearly 800 wells equally distributed operate only in the top 50 m of the aquifer. Despite the importance of these resources for providing water in the rural and urban areas, the aquifer characteristics are not well defined. The present paper aims to define first the physical and chemical characteristics of the Maastrichtian aquifer. The reserve of the aquifer initially estimated at 350 billion m3, is reassessed using new data providing from cross sections realized as part of our research, through the Water Sectorial Project of the Ministry of Hydraulics. Data from oil wells and geophysical logging are used to investigate the geometry of the aquifer and the position of the fresh/salty water interface. The highest thickness of the aquifer is between 200 to 400 m and salty water is present below the fresh groundwater in the west side of the aquifer. In the Eastern side, potable water lies directly above the basement. The thickness of the aquifer increases from the west to the center, and then decreases towards the shallow basement rock in the South East. The average thickness is 250 m. Chemical data coming from pumping wells indicate high chloride (250 - 1600 mg/l) and fluoride content (1 - 5.5 mg/l). Therefore, the reassessment has to take into account the chemical aspect of the water.
The deep and confined Maastrichtian aquifer contains considerable groundwater resources. It stretches over nearly 200,000 km2, from the northern part of Mauritania to the South of Guinea Bissau where it becomes shallow. The reservoir is composed mainly of coarse sands and sandstone interbedded with some clay units. The aquifer provides 40% of the total drinking water extracted from the different aquifers and nearly 800 wells equally distributed operate only in the top 50 m of the aquifer. Despite the importance of these resources for providing water in the rural and urban areas, the aquifer characteristics are not well defined. The present paper aims to define first the physical and chemical characteristics of the Maastrichtian aquifer. The reserve of the aquifer initially estimated at 350 billion m3, is reassessed using new data providing from cross sections realized as part of our research, through the Water Sectorial Project of the Ministry of Hydraulics. Data from oil wells and geophysical logging are used to investigate the geometry of the aquifer and the position of the fresh/salty water interface. The highest thickness of the aquifer is between 200 to 400 m and salty water is present below the fresh groundwater in the west side of the aquifer. In the Eastern side, potable water lies directly above the basement. The thickness of the aquifer increases from the west to the center, and then decreases towards the shallow basement rock in the South East. The average thickness is 250 m. Chemical data coming from pumping wells indicate high chloride (250 - 1600 mg/l) and fluoride content (1 - 5.5 mg/l). Therefore, the reassessment has to take into account the chemical aspect of the water.
Cite this paper
C. Kane, M. Diene, M. Fall, B. Sarr and A. Thiam, "Reassessment of the Resources of a Deep Aquifer System under Physical and Chemical Constraints:The Maastrichtian Aquifer," Journal of Water Resource and Protection, Vol. 4 No. 4, 2012, pp. 217-223. doi: 10.4236/jwarp.2012.44024.
C. Kane, M. Diene, M. Fall, B. Sarr and A. Thiam, "Reassessment of the Resources of a Deep Aquifer System under Physical and Chemical Constraints:The Maastrichtian Aquifer," Journal of Water Resource and Protection, Vol. 4 No. 4, 2012, pp. 217-223. doi: 10.4236/jwarp.2012.44024.
References
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[1] J. Forkasiewicz, “Maastrichtian Aquifer of the Sedimentary Basin of the Senegal-Mauritanien,” Bulletin BRGM, Vol. 3, No. 2, 1982, pp. 185-196. [2] I. Doumouya, “Summary of Properties of the Shell, Elec- trofacies and Sedimentological Facies of the Maastrich- tian Aquifer: A Tool for Establishing Equivalence,” Ph.D. Thesis, Cheikh Anta Diop University, Dakar, 1988. [3] A. Faye, “Recharge and Paleorecharge Deep Aquifers of the Basin Of Senegal. Contribution of Stable and Radio- active Isotopes in the Environment, and Paleoclimatic Im- plications Palaeohydrological,” Ph.D. Thesis, Cheikh Anta Diop University, Dakar, 1994. [4] J.-C. Bellion, “Post-Paleozoic Geodynamic History of West Africa According to the Study of Some Sedimentary Basins (Senegal, Taoudenni Iullemmenden, Chad),” Ph.D. Thesis, University of Avignon, Avignon, 1987. [5] X. Poul, Y. Vuillaume and M. Audibert, “Deep Aquifer of Senegal (Water Maestrichtian). Interpretation of Peri- odic Observations from 1967 to 1970. Interpretations of Isotopic Analysis. Hydraulic Operation of the System,” Report BRGM RME 71-035, 1971. [6] Y. Travi, “Hydrogeochemistry and Hydrogeology of the Aquifers Fluorinated Basin of Senegal. Origin and Transport Conditions of Fluoride in Groundwater,” Ph.D. Thesis, University of Paris-Sud, Orsay, 1988. [7] SGPRE-Cowi/Polyconsult, “Chemistry Survey,” Working Paper No. 6, PSE, 1999. [8] DGRH, “Campaign for Recognition by Geophysical Elec- trical. 166 Electrical Soundings, Deltaic Regions and Eas- tern Edge,” Report, CPGF Horizon, 1990. [9] B. Dieng, “Palaeohydrogeological Hydrology and Quantitative Sedimentary Basin of Senegal. Attempt to Explain the Piezometric Anomalies,” Ph.D. Thesis, Ecole Nation- male des Mines de Paris, Paris, 1987, [10] J. Le Priol and B. Dieng, “Hydrogeological Synthesis of Senegal (1984-1985). Geological Structural Photo-Inter- pretation. Geometry and Boundaries of Groundwater Aq- uifers,” Summary Report DEH, Ministry of Water, 1985. [11] Arlab, “Water Supply of ICS. Complementary Study of the Maastrichtian,” Final Report No. 183/83, 1983.