1887
Volume 2 Number 2
  • ISSN: 1569-4445
  • E-ISSN: 1873-0604

Abstract

ABSTRACT

Saltwater intrusions into shallow aquifers near the coast are an important environmental problem along the whole coastal strip of the western desert of Egypt. This phenomenon was studied in two selected coastal depressions on the eastern side of the Matruh area by a geoelectrical survey which comprised several 1D sounding points as well as 2D and 3D resistivity‐imaging surveys.

For the 2D and 3D field surveys, pole‐dipole (both forward and reverse) and pole‐pole arrays were used, respectively. The spacing between adjacent electrodes was 10 m for the 2D resistivity surveys. A 5 × 5 grid of electrodes was used for the 3D survey. The spacing between electrodes was 10 or 20 m, depending on the expected depth of freshwater in each respective area. The choice of electrode spacing was based on the results of interpretation of the depth of the freshwater–saltwater boundaries, as derived from 1D resistivity soundings using a Schlumberger array. The sounding points were distributed over the study areas and the soundings were conducted prior to the 2D and 3D survey.

The data sets were inverted using the smoothness‐constrained least‐squares method. The inversion results indicate that the subsurface resistivity distributions in the whole area are highly inhomogeneous and change rapidly within a short distance. However, from the resulting models, it was possible to correlate the ranges of resistivity with subsurface geological information available from shallow boreholes. The horizontal and vertical sections presented illustrate the configuration of the subsurface conditions that would have been, most probably, insufficiently accurate in the case of 1D modelling.

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2004-03-01
2024-04-28
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References

  1. Abd El‐LatifT. A.1973. Geophysical studies on underground water in some localities between Ras El Dabaa and Ras El Hekma, northwestern coastal zone, Egypt. PhD thesis, Cairo University, Egypt.
    [Google Scholar]
  2. Abdul NassirS.S., LokeM.H, LeeC.Y. and NawawiM.N.M.2001. Salt‐water intrusion mapping by geoelectrical imaging surveys. Geophysical Prospecting48, 647–462.
    [Google Scholar]
  3. AtawaS.M.M.1979. Hydrogeology and hydrogeochemistry of the northwestern coast of Egypt. PhD thesis, Alexandria University, Egypt.
    [Google Scholar]
  4. BarkerR.D.2001. Principles of electrical imaging.Birmingham University, UK, unpublished manuscript at://www.bham.ac.uk/earthsciences/research/hydro/envgeo/
    [Google Scholar]
  5. BazinetR.2000. Less electrodes for improved resistivity profiling. Proceedings of the 6th meeting of Environmental and Engineering Geophysics,Bochum, Germany, EL17.
    [Google Scholar]
  6. BobachevA.A., ModinI.N. and ShevninV.A.2001. IPI2Win v. 2.0: User’s Guide. Moscow State University, Geological Faculty, Dept.of Geophysics.
    [Google Scholar]
  7. ChambersJ.E., OgilvyR.D., KurasO., CrippsJ.C. and MeldrumP.I.2002. 3D electrical imaging of known targets at a controlled environmental test site. Environmental Geology41, 690–704.
    [Google Scholar]
  8. DahlinT.1996. 2D resistivity surveying for environmental and engineering applications. First Break14, 275–283.
    [Google Scholar]
  9. deGroot‐HedlinC. and ConstableS.C.1990. Occam’s inversion to generate smooth‐ dimensional models from magnetotelluric data. Geophysics55, 1613–1624.
    [Google Scholar]
  10. DeyA., MayerW.H., MorrisonH.F. and DolanW.M.1975. Electric field response of two‐dimensional inhomogeneities to unipolar and biopolar configurations. Geophysics40, 630–640.
    [Google Scholar]
  11. DeyA. and MorrisonH.F.1979. Resistivity modelling for arbitrarily shaped two‐ dimensional structures. Geophysical Prospecting27, 106–136.
    [Google Scholar]
  12. El‐FikyA.A.1996. Geophysical and hydrogeological investigations on some groundwater problems at the area between Fuka and Ras Umm El‐Rakham, Mediterranean coastal zone, Egypt. PhD thesis, Alexandria University, Egypt.
    [Google Scholar]
  13. El SenussiM.Y. and ShataA.A., 1969. The stratigraphy of Umm El Rakham area. Bulletin Inst. Desert, Egypt19(2), 1–32.
    [Google Scholar]
  14. GEOTOMO SOFTWARE
    GEOTOMO SOFTWARE2002a. RES2DINV – Manual, www.geoelectrical.com
  15. GEOTOMO SOFTWARE
    GEOTOMO SOFTWARE2002b. RES3DINV – Manual, www.geoelectrical.com
  16. LiY. and OldenburgD.W.1992. Approximate inverse mapping in DC resistivity problems. Geophysical Journal International109, 343–362.
    [Google Scholar]
  17. LokeM.H.2001. Tutorial: 2D and 3D electrical imaging surveys. Penang, Malaysia, Universiti Sains Malaysia, Unpublished course notes, www.geoelectric.com.
    [Google Scholar]
  18. LokeM.H., AcworthI. and DahlinT.2001. A comparison of smooth and blocky inversion methods in 2D electrical imaging surveys. Proceedings of 15th ASEG Geophysical Conference and Exhibition, Brisbane.
    [Google Scholar]
  19. LokeM.H. and BarkerR.D.1995. Least‐squares deconvolution of apparent resistivity pseudosections. Geophysics60, 1682–1690.
    [Google Scholar]
  20. LokeM.H. and BarkerR.1996a. Practical techniques for 3D resistivity surveys and data inversion. Geophysical Prospecting44, 499–524.
    [Google Scholar]
  21. LokeM.H. and BarkerR.D.1996b. Rapid least‐squares inversion of apparent resistivity pseudosections by a quasi‐Newton method. Geophysical Prospecting44, 131–152.
    [Google Scholar]
  22. LokeM.H. and DahlinT.1997. A combined Gauss‐Newton and quasi‐Newton inversion method for the interpretation of apparent resistivity pseudosections. Proceedings of the 3rd meeting of EEGS‐ –European Section, Aarhus, Denmark.
    [Google Scholar]
  23. LokeM.H and DahlinT.2002. A comparison of the Gauss‐Newton and quasi‐Newton methods in resistivity imaging inversion. Journal of Applied Geophysics49(3), 149–162.
    [Google Scholar]
  24. MorrisM., RønningJ.S. and LileO.B.1997. Detecting lateral resistivity inhomogeneities with the Schlumberger array. Geophysical Prospecting45, 435–448.
    [Google Scholar]
  25. PanissodC., MichotD., BenderitterY. and TabbaghA.2001. On the effectiveness of 2D electrical inversion results: an agricultural case study. Geophysical Prospecting49, 570–576.
    [Google Scholar]
  26. PatraH.P. and NathS.K.1999. Schlumberger Geoelectric Sounding in Groundwater. Balkema, Brookfield, U.S.A.
    [Google Scholar]
  27. PridmoreD.F., HohmannG.W. and WardS.H.1981. An investigation of finite‐element modeling for electrical and electromagnetic data in three dimensions. Geophysics46, 1009–1024.
    [Google Scholar]
  28. SasakiY.1989. Two‐dimensional joint inversion of magnetotelluric and dipole‐dipole resistivity data. Geophysics54, 254–262.
    [Google Scholar]
  29. SasakiY.1992. Resolution of resistivity tomography inferred from numerical simulation. Geophysical Prospecting40, 453–464.
    [Google Scholar]
  30. SasakiY.1994. 3D resistivity inversion using the finite‐element method. Geophysics59, 1839–1848.
    [Google Scholar]
  31. TelfordW.M., GeldartL.P. and SheriffR.E.1990. Applied Geophysics, 2nd edn. Cambridge University Press.
    [Google Scholar]
  32. TsourlosP.I., SzymanskiJ.I. and TsokasG.N.1998. A smoothness constrained algorithm for the fast 2D inversion of DC resistivity and induced polarization data. Journal of the Balkan Geophysical Society1, 3–13.
    [Google Scholar]
  33. Van ZijlJ.S.U.1985. A Practical Manual on the Resistivity Method. Geophysical Division, Nat. Phys, Res. Lab., Counc. for Scientific and Ind. Res., South Africa.
    [Google Scholar]
  34. WardS.H.1990. Resistivity and induced polarization methods. In: Investigations in Geophysics no.5, Geotechnical and Environmental Geophysics, Vol. I (ed. S.Ward ), pp. 147–189. Society of Exploration Geophysicists.
    [Google Scholar]
  35. ZohdyA.A.R.1989. A new method for automatic interpretation of Schlumberger and Wenner sounding curves. Geophysics54, 245–253.
    [Google Scholar]
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