Skip to main content

Advertisement

SpringerLink
Log in

The sedimentary coastal basin of Togo: example of a multilayered aquifer still influenced by a palaeo-seawater intrusion

  • Paper
  • Published:
Hydrogeology Journal Aims and scope Submit manuscript

Abstract

In Togo, the hydrogeology of the sedimentary coastal aquifers along the Gulf of Guinea has been studied for the last three decades to define the recharge processes and the origin and evolution of the salinity. Isotope hydrology and fluid geochemistry suggest that the current recharge of all aquifers, both confined and unconfined, occurs through the crystalline basement and the Plio-Quaternary deposits. Two main groundwater mineralization processes are observed: the first one, in recharge areas, is due to farming, village and city life and concerns unconfined aquifers (crystalline basement, Continental Terminal and Quaternary sediments); the second one is a mixing process between recent freshwater and fossil saline water still present in the deep confined aquifers inland, several kilometers away from the coast. Brackish water was trapped in low-permeability lenses of confined aquifers (Eo-Palaeocene and Maastrichtian) during the Quaternary, in periods of low recharge, notably during the last glacial maximum (LGM), and has not yet been flushed out. Hydrodynamic simulations indicate that, at that time, the aquifers experienced a maximum seawater intrusion as far as 20–22 km inland, depending on the palaeo-recharge value at the outcrops.

Résumé

Au Togo, l’hydrogéologie des aquifères côtiers sédimentaires le long du Golfe de Guinée a été étudiée depuis trente ans pour définir leurs processus de recharge et l’origine et l’évolution de leur salinité. L’hydrologie isotopique et la géochimie des eaux suggèrent que la recharge actuelle des tous les aquifères, libres ou captifs, se produit à travers le socle cristallin et les dépôts Plio-Quaternaires. On observe deux processus majeurs de minéralisation des eaux : le premier, dans les zones de recharge, est dû à l’activité agricole, à l’activité urbaine et villageoise, et concerne les aquifères libres (socle cristallin, Continental Terminal, et sédiments Quaternaires). Le second est un processus de mélange entre des eaux douces récentes et des eaux salées fossiles encore présentes dans les aquifères captifs profonds à l’intérieur des terres. L’eau saumâtre a été piégée dans des lentilles de faible perméabilité des aquifères captifs (Eo-Paléocène et Maestrichtien) pendant le Quaternaire, au cours des périodes de faible recharge, notamment pendant le dernier maximum glaciaire, et n’a pas été encore lessivée. Des simulations hydrodynamiques montrent que, à ces époques, les aquifères ont connu une intrusion saline allant jusqu’à 20–22 km de la côte, à terre, en fonction de la paléo-recharge aux affleurements.

Resumen

En Togo, se ha estudiado la hidrogeología de los acuíferos costeros sedimentarios a lo largo del Golfo de Guinea durante las últimas tres décadas para definir los procesos de recarga y el origen y evolución de la salinidad. La hidrología isotópica y la geoquímica de fluidos sugieren que la recarga actual a todos los acuíferos, tanto los confinados como los libres, se produce a través del basamento cristalino y los depósitos Plio-Cuaternarios. Se han observado dos procesos principales de mineralización de las aguas subterráneas: el primero, en las zonas de recarga, se debe a la agricultura y a las actividades en los pueblos y ciudades y afecta a los acuíferos libres (Basamento Cristalino, Sedimentos Continentales Terminales y Sedimentos Cuaternarios): el segundo es un proceso de mezcla entre las aguas dulces recientes y aguas salinas fósiles que están todavía presentes en pequeños acuíferos confinados tierra adentro, a algunos kilómetros de la costa. El agua salobre ha sido atrapada en lentejones de baja permeabilidad de los acuíferos confinados (Eo-Paleocenos y Maestrichtienses) durante el Cuaternario, en periodos de baja recarga, notablemente durante el último máximo interglaciar, y no han sido expulsadas. Las simulaciones hidrodinámicas indican que, en ese tiempo, los acuíferos sufrieron un máximo de intrusión marina mayor de 20 a 22 km tierra adentro, dependiendo de los valores de paleo-recarga en los afloramientos.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9

Similar content being viewed by others

References

  • Akiti TT (1977) Groundwater from the Keta-Anlo Artesian Basin. Proceedings of 10th Biennial Conference of Ghana Science Association, Cape Coast, Ghana

  • Akiti TT (1980) Etude Géochimique et Isotopique de quelques aquifères au Ghana: gneiss de la Plaine d’Accra, calcaire de la Plaine SE de la Volta, granite de la Haute Région [Geochemical and isotopic study of several aquifers in Ghana: Accra plain gneiss, SE Volta plain limestone, High Region granite] PhD Thesis, Université Paris-Sud, Orsay France, 345 pp

  • Akouvi A (2005) Etude géochimique et hydrogéologique des eaux souterraines d’un basin sédimentaires côtier en zone tropicale. Implications sur la gestion, la protection et la préservation des ressources en eau du Togo (Afrique de l’Ouest) [Geochemical and hydrogeological study of groundwater from the coastal sedimentary basin in the tropical zone: implication for management, protection and preservation of the water resources of Togo (West Africa)]. PhD Thesis, Université Pierre et Marie Curie, Paris VI, Paris, France, 163 pp

  • Bannerman RR (1994) Appraisal of the Limestone Aquifer of the Keta Basin, Ghana. In: Sovri J, Soukhl T (Eds) Future groundwater resources at risk. IAHS Publ. No. 222, IAHS, Wallingford, UK, pp 315–321

  • Bergonzini L, Chalié F, Gasse F (1997) Paleoevaporation and paleoprecipitation in the Tanganyika basin at 18,000 years B.P. inferred from hydrologic and vegetation proxies. Quat Res 47:295–305

    Article  Google Scholar 

  • Blavoux B, Dray M, Fehri A, Olive P, Groening M, Sonnntag C, Hauquin JP, Pelissier G, Pouchan P (1993) Palaeoclimatic and hydrodynamic approach to the Aquitaine basin deep aquifer (France) by means of environmental isotopes and noble gases. In: Isotope techniques in the study of Past and Current Environmental Changes in the Hydrosphere and the Atmosphere. STI/PUB/ 908, IAEA, Vienna, Austria, pp 293–305

  • BNRM (1986) Carte géologique de Togo et Notice explicative de la carte géologique au 1/200.000. Feuille de Lomé. 1ere édition [Geological map of Togo and explanatory notes at 1/200,000, Lomé sheet, 1st edition]. Mémoire n° 5, BNRM. Togo, BRGM, Orléans, France

  • Clark P, Fritz P (1997) Environmental Isotopes in Hydrogeology. Lewis, New York, 328 pp

    Google Scholar 

  • Coleman ML, Sheppard TJ, Durham JJ, Rouse JE, Moore GR (1982) Reaction of water with zinc for hydrogen isotope analysis. Anal Chem 54:993–995

    Article  Google Scholar 

  • Craig H (1957) Isotopic standards for carbon and oxygen and correlation factors for mass spectrometric analysis of carbon dioxide. Geochim Cosmochim Acta 12:133–149

    Article  Google Scholar 

  • Craig H (1961) Isotopic variation in meteoric waters. Science 133:1702–1703

    Article  Google Scholar 

  • Dansgaard W (1964) Stable isotopes in precipitation. Tellus 16(4):436–468

    Article  Google Scholar 

  • Dapaah-Siakwan S, Gyau-Boakye P (2000) Hydrogeological framework and borehole yields in Ghana. Hydrogeol J 8(4):405–416

    Article  Google Scholar 

  • DHE (1982) Surveillance piézométrique et chimique des nappes du bassin sédimentaire côtier du Togo. Synthèse des connaissances hydrogéologiques [Piezometric and chemical monitoring of the Togo coastal sedimentary aquifers: hydrogeological data synthesis]. Rapport 82 AGE 036, DHE-Togo, BRGM, Orléans, France

  • DHE (1983) Alimentation en eau de Lomé. Ressources en eau souterraine. Synthèse des données hydrogéologiques [Water supply for Lomé: groundwater resources, hydrogeological data synthesis]. Rapport 83 AGE 040, DHE-Togo, BRGM, Orléans, France

  • Dodo A, Zuppi GM (1999) Variabilité climatique durant le Quaternaire dans la nappe du Tarat (Arlit, Niger) [Climatic variability during the Quaternary in the Tarat aquifer (Arlit, Niger)]. CR Acad Sci Earth Planet Sci 328:371–379

    Google Scholar 

  • Dray M, Gonfiantini R, Payne BR, Zuppi GM (1980) Exemples d’application des isotopes du milieu à des problèmes d’hydrologie souterraine en Afrique [Examples of the use of environmental isotopes to groundwater hydrology problems]. CR dixième réunion conseil Com Interafricain Etud Hydraul 2:355–370

    Google Scholar 

  • Dray M, Giachello L, Lazzarotto V, Mancini M, Roman E, Zuppi GM (1989) Etude isotopique de l’aquifère crétacé du bassin béninois [Isotopic study of the Cretaceous aquifer of the Benin basin]. Hydrogéologie 3:167–177

    Google Scholar 

  • Edmunds WM, Droubi K (1997) Groundwater salinity and environmental change. In: Isotope techniques in the study of past and current environment changes in the hydrosphere and the atmosphere, STI/PUB/1024, IAEA, Vienna, Austria, pp 503–518

  • Epstein S, Mayeda TK (1953) Variations of the 18O/16O ratio in natural waters. Geochim Cosmochim Acta 4:213–224

    Article  Google Scholar 

  • Fontaine B (1991) Variations pluviométriques et connexions climatiques: l’exemple des aires de moussons indienne et ouest-africaine [Rainfall variations and climatic connexions: example of the monsoon areas of India and West Africa]. Sécheresse 4:259–264

    Google Scholar 

  • Fontes JC, Gasse F (1991) PALHYDAF (palaeohydrology in Africa) program: objectives, methods, major results. Palaeogeog Palaeoclim Palaeoecol 84:191–215

    Article  Google Scholar 

  • Fontes JC, Matray JM (1993) Geochemistry and origin of formation brines from the Paris Basin, France: 1. brines associated with Triassic salts. Chem Geol 109(1–4):149–175

    Article  Google Scholar 

  • Fontes JC, Gasse F, Andrews JN (1993) Climatic conditions of Holocene groundwater recharge in the Sahel zone of Africa. In: Isotope Techniques in the Study of Past and Current Environmental Changes in the Hydrosphere and the Atmosphere. IAEA-SM-329/59, IAEA, Vienna, Austria

  • Fritz P, Frape S (1987) Saline water and gases in crystalline rocks. Geol Assoc Can Spec Pap 33:259

    Google Scholar 

  • Gallo G (1974) Rapport final sur les études isotopiques appliquées à l’hydrogéologie du bassin sédimentaire côtier du Togo [Final report on the isotopic studies applied to the hydrogeology of the sedimentary basin of Togo]. IAEA Internal Report TOG 71/511, IAEA, Vienna, Austria

  • Gasse F (2000) Hydrological changes in the African tropics since the Last Glacial Maximum. Quat Sci Rev 19(1–5):189–211

    Article  Google Scholar 

  • Gonfiantini R, Stichler W, Rozanski K (1995) Standards and intercomparison materials distributed by the International Atomic Energy Agency for stable isotope measurements. In: Reference and intercomparison materials for stable isotopes of light elements. IAEA-TECDOC-825, IAEA, Vienna, Austria, pp 13–29

  • Helstrup T, Jørgensen NO, Banoeng-Yakubo B (2007) Investigation of hydrochemical characteristics of groundwater from the Cretaceous-Eocene limestone aquifer in southern Ghana and southern Togo using hierarchical cluster analysis. Hydrogeol J 15(5):977–989

    Article  Google Scholar 

  • Johnson AKC (1987) Le bassin côtier à phosphates du Togo (Maastrichtien-Eocène moyen) [The coastal phosphatic basin of Togo (Maastrichtian-Middle Eocene)]. PhD Thesis, Université de Bourgogne et Université du Bénin (Togo), Dijon, France, and Lomé, Togo, 360 pp

  • Johnson AKC, Rat P, Lang J (2000) Le bassin sédimentaire à phosphates du Togo (Maastrichtien-Eocène): stratigraphie, environnements et évolution [The phosphate sedimentary basin of Togo (Maastrichtian-Eocene): stratigraphy, environments and evolution]. J African Earth Sci 30(1):183–200

    Article  Google Scholar 

  • Kroopnick P (1974) The dissolved O2–CO2–13C system in the eastern equatorial Pacific. Deep-Sea Res 21:211–227

    Google Scholar 

  • Le Barbé L, Lebel T (1997) Rainfall climatology of the HAPEX-Sahel region, during the years 1950–1990. J Hydrol 188–189:43–73

    Article  Google Scholar 

  • Le Barbé L, Ale G, Millet B, Texier Y, Borel Y, Gualde R (1993) Les ressources en eaux superficielles de la République du Bénin [Surface water resources of the Benin Republic]. Orstom, Paris, France, 540 pp

    Google Scholar 

  • Ledoux E, Sauvagnac S, Rivera A (1990) A compatible single-phase/two phase numerical model: 1. modelling the transient salt-water/fresh-water interface motion. Ground Water 28(1):79–87

    Article  Google Scholar 

  • Marlin C, Oga MS, Dever L (1999) Recharge estimation of two unconfined aquifers near Abidjan (Ivory Coast). International Symposium on Isotope Techniques in Water Resources Development and Management. IAEA-SM-361, electronic proceedings. IAEA, Vienna, Austria

    Google Scholar 

  • Mas-Pla J, Bach J, Viñals E, Trilla J, Estralrich J (1999) Salinization processes in a coastal leaky aquifer system (Alt Empordà, NE Spain). Phys Chem Earth, Part B Hydrol Oceans Atmos 24(4):337–341

    Article  Google Scholar 

  • Mathieu R, Bariac T, Fouillac C, Guillot B, Mariotti A (1993) Variation en isotopes stables dans les précipitations en 1988 et 1989 au Burkina Faso ; apports de la météorologie régionale [Stable isotopes variations in rainfall in 1988 and 189 in Burkina-Faso: contributions of regional meteorology]. ORSTOM-METEO FRANCE, Veille Climatique Satellitaire 45:47–64

    Google Scholar 

  • Mbonou A, Travi Y (1994) Labelling of precipitation by stable isotopes (18O, 2H) over the Jos Plateau and the surrounding plains (north central Nigeria). J African Earth Sci 19:91–98

    Article  Google Scholar 

  • Nielsen L, Jørgensen NO, Gelting P (2007) Mapping of the freshwater lens in a coastal aquifer on the Keta Barrier (Ghana) by transient electromagnetic soundings. J Appl Geophys 62(1):1–15

    Article  Google Scholar 

  • Oga YMS (1998) Ressources en eaux souterraines dans la région du Grand Abidjan (Côte d’Ivoire): Approches hydrochimique et isotopique [Groundwater resources in the Abidjan surroundings (Ivory Coast): hydrochemical and isotopic approaches]. PhD Thesis, Université Paris-Sud, Orsay, France, 299 pp

  • Olive P (2000) La datation des eaux souterraines à long temps de résidence par le radiocarbone. Mode d’emploi [Groundwater dating for long residence times by radiocarbon: users’ guide]. Hydrogéologie 1:3–19

    Google Scholar 

  • Raoult Y (1999) La nappe de l’Albien dans le bassin de Paris: de nouvelles idées pour de vieilles eaux [The Albian aquifer in the Paris basin: new ideas for old water]. PhD Thesis, Université Pierre et Marie Curie-Paris VI, Paris, France, 190 pp

  • Shakleton NJ (1987) Oxygen isotopes, ice volume and sea level. Quat Sci Rev 6:183–190

    Article  Google Scholar 

  • Sora N, Goula Bi Tié A (1997) Hydrochimie et isotopes de l’environnement appliqués à l’étude des eaux souterraines du sud de la côte d’Ivoire [Hydrochemistry and environmental isotopes for the study of groundwater in southern Ivory Coast]. Proceedings of the Rabat Symposium, Rabot, Morocco, April 1997. IAHS Publ 244:105–113

    Google Scholar 

  • Stute M, Schlosser P (1993) Principles and applications of the noble gas palaeothermometer. In: Swart PK, Lohmann KC, McKenzie J, Savin S (eds) Climate change in continental isotopic records, Geophysical Monograph 78. American Geophysical Union, Washington, DC, pp 89–100

    Google Scholar 

  • Talbot MR, Johannessen T (1992) A high resolution palaeoclimatic record of the last 27,500 years in tropical West Africa from the carbon and nitrogen isotopic composition of lacustrine organic matter. Earth Planet Sci Lett 110:23–37

    Article  Google Scholar 

  • Taupin JD, Coudrain-Ribstein A, Gallaire R, Zuppi GM, Filly A (2000) Rainfall characteristics (δ18O, δ2H, ΔT and ΔHr) in western Africa, regional scale and influence of irrigated areas. J Geophys Res 105(D9):11911–11924

    Article  Google Scholar 

  • Vengosh A, Pankratov S (1998) Chloride/bromide and chloride/fluoride ratios of domestic sewage effluents and associated contaminated ground water. Ground Water 36:815–824

    Article  Google Scholar 

  • Vengosh A, Rosenthal E (1994) Saline groundwater in Israel: its bearing on the water crisis in the country. J Hydrology 156(1–4):389–430

    Article  Google Scholar 

  • Waelbroeck C, Labeyrie L, Michel E, Duplessy JC, McManus JF, Lambeck K, Balbon E, Labracherie M (2002) Sea-level and deep water temperature changes derived from benthic foraminifera isotopic records. Quat Sci Rev 21(1–3):295–305

    Article  Google Scholar 

  • Weyhenmeyer CE, Burns SJ, Weber HN, Aeschbach-Hertig W, Kipfer R, Loosli HH, Matter A (2000) Cool glacial temperatures and changes in moisture source recorded in Oman groundwater. Science 287:842–845

    Article  Google Scholar 

Download references

Acknowledgements

The authors would like to express their gratitude to the Managing Editor, Prof. C. Simmons, the anonymous associate editor and three anonymous reviewers for their helpful comments on an earlier draft of this article, which they greatly helped to improve.

Author information

Author notes

  1. Ari Akouvi

    Present address: Burgéap, 27, rue de Vanves, 92772, Boulogne-Billancourt Cedex, France

  2. Gian Maria Zuppi

    Present address: Dipartimento di Scienze Ambientali, Università Ca’ Foscari di Venezia, Dorsoduro 2137, 30123, Venice, Italia

Authors and Affiliations

  1. Université Pierre et Marie Curie-Paris 6, UMR 7619-Sisyphe, Case 105, 4, place Jussieu, 75252, Paris Cedex 05, France

    Ari Akouvi, Sophie Violette & Ghislain de Marsily

  2. CNRS, UMR 7619 Sisyphe, Case 105, 4, place Jussieu, 75005, Paris Cedex 05, France

    Ari Akouvi, Sophie Violette & Ghislain de Marsily

  3. Université Pierre et Marie Curie-Paris 6, Centre de Recherches Géodynamiques, BP 510, 47, avenue de Corzent, 74203, Thonon cedex, France

    Martial Dray

  4. Dipartimento di Scienze della Terra, Università di Torino, Laboratorio di Idrogeologia e Geochimica Applicata, Via Valperga Caluso 35, 10125, Torino, Italia

    Gian Maria Zuppi

Authors
  1. Ari Akouvi
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Martial Dray
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Sophie Violette
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Ghislain de Marsily
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Gian Maria Zuppi
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Ghislain de Marsily.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Akouvi, A., Dray, M., Violette, S. et al. The sedimentary coastal basin of Togo: example of a multilayered aquifer still influenced by a palaeo-seawater intrusion. Hydrogeol J 16, 419–436 (2008). https://doi.org/10.1007/s10040-007-0246-1

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s10040-007-0246-1

Keywords

Search

Navigation