B.F. Alemaw, T.R. Chaoka, and T.L. Masaka (Botswana)
Remote sensing, Landsat TM, fracture density analysis, groundwater resources evaluation, Botswana, and Southern AfricaI
This paper presents results of a study on the application of remote sensing products for groundwater resources assessment. Visible, near-infrared and short wave infrared reflectance data of Landsat TM have been processed and interpreted in framework of a groundwater resources evaluation project through mapping of selected groundwater zones. A combination of spectral analysis, statistical analysis and visual extraction of lineaments from Landsat TM remote sensing was used. Detailed analysis of Optimum Index Factor (OIF) and Principal Component Analysis (PCA) enabled the validation and the revision of the lithological boundaries defined on previous geological map, and provided information for characterizing new lithological units corresponding to surface formations previously unrecognized. The optimized OIF and PCA band images were draped onto topographic images developed from DEM (SRTM data) and vegetation indicator satellite imagery maps or NDVI to extract and refine lineations that are indicators of groundwater occurrence in these fracture-related aquifers. Fracture density analysis of the composite lineaments extracted from remote sensing imagery and topographic and vegetation-related information revealed the existence of predominant fracture orientations in a main direction NW-SE compounded which appeared the primary lineament direction with north-easterly secondary dimension with several ‘micro-elements’ identified from different satellite image band combinations.
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