Discriminating Weathering Degree by Integrating Optical Sensor and SAR Satellite Images for Potential Mapping of Groundwater Resources in Basement Aquifers of Semiarid Regions

  • Luís André Magaia
  • Katsuaki Koike
  • Tada-nori Goto
  • Alaa Ahmed Masoud
Original Paper


Unlike in coastal and sedimentary basins, regional-scale exploration of groundwater resources using only geophysical methods is costlier in consolidated rocks such as volcanic rocks and crystalline basement complexes in Africa because of the highly heterogeneous structure of aquifers. Therefore, advanced analysis of remotely sensed images and an accurate assessment of groundwater resources are crucial before carrying out a geophysical prospecting survey. This study proposed a joint analysis of satellite images from optical sensors and synthetic aperture radar (SAR) which aimed to enhance potential mapping accuracy of groundwater resources in crystalline rock areas in a semiarid region. The backscattering coefficient of the SAR data analysis effectively detected the zones of relatively high weathering degree and thus having thick permeable regolith. In addition, a modified clay index calculated from the four band reflectances of the optical sensor image—red, near infrared, and two shortwave infrared bands—was applied to discriminate clay-rich zones from high vegetation activity zones. The clay-rich zones detected corresponded with the highly weathered zones estimated from the small SAR backscattering coefficients. The zones also corresponded with a large density of faults and lineaments and furthermore were verified by high potential yields from groundwater wells. The thickness of weathered zones was likely to increase with a decreasing backscattering coefficient and higher modified clay index values. Conversely, large backscattering coefficients in the narrow zones along the major lineaments from large volumetric scattering because of high vegetation activity, as confirmed by the large vegetation index values, suggested that high moisture content was retained in the soils. In fact, the potential yields of the groundwater wells tended to increase near the lineaments. Accordingly, shallow groundwater occurrence is plausible in those zones.


Regolith Backscattering coefficient Vegetation index Clay index Lineament Mozambique 



We thank the Japan International Cooperation Agency (JICA) for supporting this study and the Water and Sanitation Division of Tete Province (DAS-Tete) in Mozambique for providing the groundwater well data. This work was partially supported by JSPS KAKENHI (Grant Number 18H01924). Sincere thanks are extended to two anonymous reviewers and Editor-in-Chief Dr. John Carranza for their valuable comments and suggestions that helped improve the clarity of the manuscript.


  1. Acworth, R. I. (1987). The development of crystalline basement aquifers in a tropical environment. Quarterly Journal of Engineering Geology and Hydrogeology, 20(4), 265–272. Scholar
  2. Asf, DAAC. (2015). ALOS PALSAR_radiometric_terrain_corrected_high_res; includes material JAXA/METI 2007. Accessed through ASF DAAC,, August 25, 2017.
  3. Bishop, J. L., Michalski, J. R., & Carter, J. (2017). Remote detection of clay minerals. Developments in Clay Science, 8, 482–514. Scholar
  4. CGS. (2007). Map explanation: Sheets Furancungo (1433) and Ulongue (1434), scale 1:250,000. Maputo: Ministério dos Recursos Minerais, Direcção Nacional de Geologia.Google Scholar
  5. Chilton, P. J., & Foster, S. S. D. (1995). Hydrogeological characterisation and water-supply potential of basement aquifers in Tropical Africa. Hydrogeology Journal, 3(1), 36–49. Scholar
  6. Chirindja, F. J., Dahlin, T., & Juizo, D. (2017). Improving the groundwater-well siting approach in consolidated rock in Nampula Province. Mozambique. Hydrogeology Journal, 25(5), 1423–1435. Scholar
  7. Corgne, S., Magagi, R., Yergeau, M., & Sylla, D. (2010). An integrated approach to hydro-geological lineament mapping of a semi-arid region of West Africa using Radarsat-1 and GIS. Remote Sensing of Environment, 114(9), 1863–1875. Scholar
  8. Dill, H. G. (2016). Kaolin: Soil, rock and ore: From the mineral to the magmatic, sedimentary and metamorphic environments. Earth-Science Reviews, 161, 16–129. Scholar
  9. DNA. (1987). Carta hidrogeológica escala 1:1,000,000 1 a edição. Maputo: Ministério de Construção e Águas, Direcção Nacional de Águas.Google Scholar
  10. DNG. (2006). Geological sheet 1:250,000, No. 1434. Maputo: Ministério dos Recursos Minerais, Direcção Nacional de Geologia.Google Scholar
  11. Ducart, D. F., Silva, A. M., Toledo, C. L. B., & de Assis, L. M. (2016). Mapping iron oxides with Landsat-8/OLI and EO-1/Hyperion imagery from the Serra Norte iron deposits in the Carajás Mineral Province, Brazil. Brazilian Journal of Geology, 46(3), 331–349. Scholar
  12. Ehlen, J. (2002). Some effects of weathering on joints in granitic rocks. CATENA, 49(1–2), 91–109. Scholar
  13. Engman, E. T. (1991). Application of microwave remote sensing of soil moisture for water resources and agriculture. Remote Sensing of Environment, 35(2–3), 213–226. Scholar
  14. Foster, S. (2012). Hard-rock aquifers in tropical regions: Using science to inform development and management policy. Hydrogeology Journal, 20(4), 659–672. Scholar
  15. Gharechelou, S., Tateishi, R., & Sumantyo, J. T. S. (2015). Interrelationship analysis of L-band backscattering intensity and soil dielectric constant for soil moisture retrieval using PALSAR data. Advances in Remote Sensing, 4(1), 15–24. Scholar
  16. Hallikainen, M. T., Ulaby, F. T., Dobson, M. C., El-Rayes, M. A., & Wu, L.-K. (1985). Microwave dielectric behavior of wet soil-part I: Empirical models and experimental observations. IEEE Transactions on Geoscience and Remote Sensing, GE-23(1), 25–34. Scholar
  17. Jones, M. J. (1985). The weathered zone aquifers of the basement complex areas of Africa. Quarterly Journal of Engineering Geology and Hydrogeology, 18(1), 35–46. Scholar
  18. Jordan, C. F. (1969). Derivation of Leaf-Area Index from quality of light on the forest floor. Ecology, 50(4), 663–666. Scholar
  19. Koch, M., & Mather, P. M. (1997). Lineament mapping for groundwater resource assessment: A comparison of digital Synthetic Aperture Radar (SAR) imagery and stereoscopic Large Format Camera (LFC) photographs in the Red Sea Hills, Sudan. International Journal of Remote Sensing, 18(7), 1465–1482. Scholar
  20. Kornelsen, K. C., & Coulibaly, P. (2013). Advances in soil moisture retrieval from synthetic aperture radar and hydrological applications. Journal of Hydrology, 476, 460–489. Scholar
  21. Laur, H., Bally, P., Meadows, P., Sanchez, J., Schaettler, B., Lopinto, E., et al. (2004). ERS SAR calibration: Derivation of the backscattering coefficient σ0 in ESA ERS SAR PRI products. ESA Document No. ES-TN-RE-PM-HL09, Issue 2, Rev. 5f. Noordjiwk, The Netherlands.
  22. Magaia, L. A., Goto, T., Masoud, A. A., & Koike, K. (2018). Identifying groundwater potential in crystalline basement rocks using remote sensing and electromagnetic sounding techniques in central Western Mozambique. Natural Resources Research, 27(3), 275–298. Scholar
  23. Matricardi, E. A. T., Skole, D. L., Pedlowski, M. A., Chomentowski, W., & Fernandes, L. C. (2010). Assessment of tropical forest degradation by selective logging and fire using Landsat imagery. Remote Sensing of Environment, 114(5), 1117–1129. Scholar
  24. McCauley, J. F., Schaber, G. G., Breed, C. S., Grolier, M. J., Haynes, C. V., Issawi, B., et al. (1982). Subsurface valleys and geoarcheology of the Eastern Sahara revealed by Shuttle Radar. Science, 218(4576), 1004–1020. Scholar
  25. Miranda, N., & Meadows, P. J. (2015). Radiometric calibration of S-1 level-1 products generated by the S-1 IPF. Ref. ESA-EOPG-CSCOP-TN-0002, Issue 1, Rev. 0.
  26. Mueller-Wilm, U. (2017). S2 MPC: Sen2Cor Software Release Note. Ref. S2-PDGS-MPC-L2A-SRN-V2.4.0, Issue 02. ESA.
  27. National Research Council (1996). Rock fractures and fluid flow: Contemporary understanding and applications. Washington, DC: The National Academies Press.
  28. Okada, K., Segawa, K., & Hayashi, I. (1993). Removal of the vegetation effect from LANDSAT TM and GER imaging spectroradiometer data. ISPRS Journal of Photogrammetry and Remote Sensing, 48(6), 16–27. Scholar
  29. Ouerghemmi, W., Gomez, C., Naceur, S., & Lagacherie, P. (2016). Semi-blind source separation for the estimation of the clay content over semi-vegetated areas using VNIR/SWIR hyperspectral airborne data. Remote Sensing of Environment, 181, 251–263. Scholar
  30. Owen, R., Maziti, A., & Dahlin, T. (2007). The relationship between regional stress field, fracture orientation and depth of weathering and implications for groundwater prospecting in crystalline rocks. Hydrogeology Journal, 15(7), 1231–1238. Scholar
  31. Petrakis, R., Wu, Z., McVay, J., Middleton, B., Dye, D., & Vogel, J. (2016). Vegetative response to water availability on the San Carlos Apache Reservation. Forest Ecology and Management, 378, 14–23. Scholar
  32. Qi, J., Chehbouni, A., Huete, A. R., Kerr, Y. H., & Sorooshian, S. (1994). A modified soil adjusted vegetation index. Remote Sensing of Environment, 48(2), 119–126. Scholar
  33. Rees, W. G. (2001). Physical principles of remote sensing (2nd ed.). Cambridge: Cambridge University Press. Scholar
  34. Rocchi, I., Coop, M. R., & Maccarini, M. (2017). The effects of weathering on the physical and mechanical properties of igneous and metamorphic saprolites. Engineering Geology, 231, 56–67. Scholar
  35. Rondeaux, G., Steven, M., & Baret, F. (1996). Optimization of soil-adjusted vegetation indices. Remote Sensing of Environment, 55(2), 95–107. Scholar
  36. Rosenqvist, A., Shimada, M., Ito, N., & Watanabe, M. (2007). ALOS PALSAR: A pathfinder mission for global-scale monitoring of the environment. IEEE Transactions on Geoscience and Remote Sensing, 45(11), 3307–3316. Scholar
  37. Sabaghy, S., Walker, J. P., Renzullo, L. J., & Jackson, T. J. (2018). Spatially enhanced passive microwave derived soil moisture: Capabilities and opportunities. Remote Sensing of Environment, 209, 551–580. Scholar
  38. Sabins, F. (1999). Remote sensing for mineral exploration. Ore Geology Reviews, 14(3–4), 157–183. Scholar
  39. Saepuloh, A., Koike, K., Urai, M., & Sri Sumantyo, J. T. (2015). Identifying surface materials on an active volcano by deriving dielectric permittivity from polarimetric SAR data. IEEE Geoscience and Remote Sensing Letters, 12(8), 1620–1624. Scholar
  40. Segal, D. B., & Merin, I. S. (1989). Successful use of Landsat Thematic Mapper data for mapping hydrocarbon microseepage-induced mineralogic alteration, Lisbon Valley, Utah. Photogrammetric Engineering and Remote Sensing, 55(8), 1137–1145.Google Scholar
  41. Shaban, A., Khawlie, M., & Abdallah, C. (2006). Use of remote sensing and GIS to determine recharge potential zones: The case of Occidental Lebanon. Hydrogeology Journal, 14(4), 433–443. Scholar
  42. Shi, J., Wang, J., Hsu, A. Y., O’Neill, P. E., & Engman, E. T. (1997). Estimation of bare surface soil moisture and surface roughness parameter using L-band SAR image data. IEEE Transactions on Geoscience and Remote Sensing, 35(5), 1254–1266. Scholar
  43. Shimada, M., Isoguchi, O., Tadono, T., & Isono, K. (2009). PALSAR radiometric and geometric calibration. IEEE Transactions on Geoscience and Remote Sensing, 47(12), 3915–3932. Scholar
  44. Singhal, B. B. S., & Gupta, R. P. (2010). Applied hydrogeology of fractured rocks (2nd ed.). Berlin: Springer. Scholar
  45. Small, D., & Schubert, A. (2008). Guide to ASAR Geocoding. Ref. RSL-ASAR-GC-AD, Issue 1.01. RSL, University of Zürich.
  46. Trudel, M., Charbonneau, F., & Leconte, R. (2012). Using RADARSAT-2 polarimetric and ENVISAT-ASAR dual-polarization data for estimating soil moisture over agricultural fields. Canadian Journal of Remote Sensing, 38(4), 514–527. Scholar
  47. Wilford, J. R., Searle, R., Thomas, M., Pagendam, D., & Grundy, M. J. (2016). A regolith depth map of the Australian continent. Geoderma, 266, 1–13. Scholar
  48. Worthington, S. R. H., Davies, G. J., & Alexander, E. C. (2016). Enhancement of bedrock permeability by weathering. Earth-Science Reviews, 160, 188–202. Scholar
  49. Wright, E. P. (1992). The hydrogeology of crystalline basement aquifers in Africa. Hydrogeology of Crystalline Basement Aquifers in Africa Geological Society Special Publication, 66, 1–27. Scholar
  50. Yu, B., Liu, G., Liu, Q., Wang, X., Feng, J., & Huang, C. (2018). Soil moisture variations at different topographic domains and land use types in the semi-arid Loess Plateau, China. CATENA, 165, 125–132. Scholar

Copyright information

© International Association for Mathematical Geosciences 2018

Authors and Affiliations

  1. 1.Department of Urban Management, Graduate School of EngineeringKyoto UniversityKyotoJapan
  2. 2.Geology Department, Faculty of SciencesEduardo Mondlane UniversityMaputoMozambique
  3. 3.Geology Department, Faculty of ScienceTanta UniversityTantaEgypt

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