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 JWARP  Vol.9 No.13 , December 2017
Hydrochemical and Isotopic Characteristics of the Basement Aquifer in the Wadi Fira Area, Eastern Chad
Abstract: The Wadi-Fira region in eastern Chad is facing dramatic water supply problems, related to the climatic semi-arid context and the reception of refugees from the Darfour, which has increased the local population by 22% these last years. Expansion of agglomerations (temporary new towns), development of agricultural and pastoral practices together with the augmentation of the population have led to dramatic water needs. The basement aquifer of Wadi-Fira constitutes the main source of water supply. However, little is known about this system. Within this context, this work aims at better understanding and identifying hydrogeochemical processes and their relations to groundwater quality within this complex environment, and groundwater recharge mechanisms. 31 groundwater samples were collected at two sites, Am Zoer and Guereda-Iriba, from hand dug wells and deep wells. Major chemical elements were analyzed on all samples and stables isotopes (oxygen-18 and deuterium) on 17 samples. Various methods were used to interpret the hydrochemical data (descriptive and multivariate statistics, Piper and Schoeller diagrams, scatter plots, minerals saturation indices). The stable isotopes were interpreted using conventional IAEA methods. The results permitted to differentiate the laterite reservoir from the deep fractured reservoir. The main process controlling groundwater mineralization is water-rocks interaction and natural minerals dissolution. Ion exchanges, evaporation and anthropogenic activities have also a moderate impact on groundwater quality. Based on isotopes data, it is concluded that groundwater in the basement aquifer is related with modern rainfall. These results provide further insights into this basement aquifer, which is a vital resource for the region of Wadi-Fira.
Cite this paper: Mahamat, H. , Coz, M. , Abderamane, H. , Sardini, P. and Razack, M. (2017) Hydrochemical and Isotopic Characteristics of the Basement Aquifer in the Wadi Fira Area, Eastern Chad. Journal of Water Resource and Protection, 9, 1688-1708. doi: 10.4236/jwarp.2017.913105.
References

[1]   Sonet, J. (1963) Explanatory Booklet on the Niéré Sheet. Reconnaissance Geological Map of Chad at 1/500,000. BRGM, Orléans.

[2]   Isseini, M. (2011) Crustal Growth and Differentiation during the Neoproterozoic Example of the Pan-African Domain of Mayo Kebbi in Southwestern Chad. PhD Thesis, University Henri Poincaré, Nancy.

[3]   Wyns, R., Baltassat, J.M., Lachassagne, P., Legchenko, A., Vairon, J. and Mathieu, F. (2004) Application of SNMR Soundings for Groundwater Reserves Mapping in Weathered Basement Rocks (Brittany, France). Bulletin de la Société Géologique de France, 175, 21-34.
https://doi.org/10.2113/175.1.21

[4]   Chilton, P.J. and Foster, S.S.D. (1995) Hydrogeological Characterization and Water-Supply Potential of Basement Aquifers in Tropical Africa. Hydrogeology Journal, 3, 36-49.
https://doi.org/10.1007/s100400050061

[5]   Maréchal, J.C., Dewandel, B., Subrahmanyam, K. and Torri, R. (2003) Review of Specific Methods for the Evaluation of Hydraulic Properties in Fractured Hard-Rock Aquifers. Current Science, 85, 516.

[6]   Acworth, R.I. (1987) The Development of Crystalline Basement Aquifers in a Tropical Environment. Quarterly Journal of Engineering Geology, 20, 265-272.
https://doi.org/10.1144/GSL.QJEG.1987.020.04.02

[7]   Cho, M., Ha, K.-M., Choi, Y.-S., Kee, W.-S., Lachassagne, P. and Wyns, R. (2003) Relationship between the Permeability of Hard-Rock Aquifers and Their Weathered Cover Based on Geological and Hydrogeological Observation in South Korea. IAH Conference on Groundwater in Fractured Rocks, Prague, 15-19 September 2003, 41-43.

[8]   Craig, H. (1961) Isotopic Variations in Meteoric Waters. Science, 133, 1702-1703.
https://doi.org/10.1126/science.133.3465.1702

[9]   Piper, A.M. (1944) A Graphic Procedure in the Geochemical Interpretation of Water Analyses. Transactions—American Geophysical Union, 25, 914-923.

[10]   IAEA (2007) Global Network of Isotopes in Precipitation (GNIP) Database IAEA/WMO, Vienna, Austria.
https://nucleus.iaea.org/Pages/GNIPR.aspx

[11]   Langmuir, D. (1997) Aqueous Environmental Geochemistry. Prentice Hall, Upper Saddle River.

[12]   Swan, A.R.H. and Sandilands, M. (1995) Introduction to Geological Data Analysis. Blackwell, Oxford.

[13]   WHO (1984) Guidelines for Drinking Water Quality. World Health Organization, Geneva.

[14]   Furi, W., Razack, M., Abiye, T.A., Kebede, S. and Legesse, D. (2012) Hydrochemical Characterization of Complex Volcanic Aquifers in a Continental Rifted Zone: The Middle Awash Basin, Ethiopia. Hydrogeology Journal, 20, 385-400.
https://doi.org/10.1007/s10040-011-0807-1

[15]   Steinhorst, R.K. and Williams, R.E. (1985) Discrimination of Groundwater Sources using Cluster Analysis, MANOVA, Canonical Analysis and Discriminant Analysis. Water Resources Research, 21, 1149-1156.

[16]   Dawdy, D.R. and Feth, J.H. (1967) Application of Factor Analysis in Study of Chemistry of Groundwater Quality, Mojave River Valley, California. Water Resources Research, 3, 505-510.

[17]   Dalton, M.G. and Upchurch, S.B. (1978) Interpretation of Hydrochemical Facies by Factor Analysis. Ground Water, 16, 228-233.

[18]   Schoeller, H. (1967) Geochemistry of Groundwater. An International Guide for Research and Practice. UNESCO, Chap 15, 1-18.

[19]   Meybeck, M. (1987) Global Chemical Weathering of Surficial Rocks Estimated from River Dissolved Loads. American Journal of Science, 287, 401-428.
https://doi.org/10.2475/ajs.287.5.401

[20]   Edmunds, W.M., Kay, R.L.F., Miles, D.L. and Cook, J.M. (1987) The Origin of Saline Groundwaters in the Carnmenellis Granite, Cornwall (UK): Further Evidence from Minor and Trace Elements. In: Fritz, P. and Frape, S.K., Eds., Saline Water and Gases in Crystalline Rocks, Geological Association of Canada Special Paper 33, Geological Association of Canada, St. John’s, 127-143.

[21]   Appelo, C.A.J. and Postma, D. (1996) Geochemistry, Groundwater and Pollution. Balkema, Rotterdam, 536.

[22]   Parkhurst, D.L. and Appelo, C.A.J. (1999) User’s Guide to PHREEQC (Version 2)—A Computer Program for Speciation, Batch-Reaction, One-Dimensional Transport, and Inverse Geochemical Calculations. United States Geological Survey, Water Resources Investigations Report 99-4259, Washington DC, 326.

[23]   Gibbs, R. (1970) Mechanism Controlling World River Water Chemistry. Science, 170, 1088-1090.
https://doi.org/10.1126/science.170.3962.1088

[24]   Fisher, R.S. and Mulican III, W.F. (1997) Hydrochemical Evolution of Sodium-Sulfate and Sodium-Chloride Groundwater beneath the Northern Chihuahuan Desert, Trans-Pecos, Rexas, USA. Hydrogeology Journal, 10, 455-47

 
 
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