Original Paper Identifying Groundwater Potential in Crystalline Basement Rocks Using Remote Sensing and Electromagnetic Sounding Techniques in Central Western Mozambique Luı´s Andre ´ Magaia, 1,2 Tada-nori Goto, 1 Alaa Ahmed Masoud, 3 and Katsuaki Koike 1,4 Received 16 August 2017; accepted 14 November 2017 Exploring for groundwater in crystalline rocks in semiarid areas is a challenge because of their complex hydrogeology and low potential yields. An integrated approach was applied in central western Mozambique, in an area covered by Precambrian crystalline basement rocks. The approach combined a digital elevation model (DEM), remote sensing, and a ground- based geophysical survey. The aim was to identify groundwater zones with high potential and to identify geological structures controlling that potential. Lineaments were extracted from the DEM that had been enhanced using an adaptive-tilt, multi-directional, shading technique and a non-filtering technique to characterize the regional fracture system. The shallowness and amount of stored groundwater in the fracture zones was assessed using vegetation indices derived from Landsat 8 OLI images. Then, 14 transient electromagnetic (TEM) survey profiles were taken in different geological settings across continuous linea- ments that were considered to be aligned along inferred faults. In the central lineament zones, the TEM soundings gave resistivity values of less than 300 Xm at a depth of 20–80 m. The values varied with location. Conversely, values greater than 400 Xm were observed at the sites away from the central zones. This contrast is probably caused by the differences in permeability and degree of weathering along the fractured zones. These differences could be key factors in determining groundwater occurrence. By integrating five water-related factors (lineament density, slope, geology, vegetation index, and proximity to lineaments), high groundwater potential zones were located in the vicinity of the lineaments. In these zones, vegetation remains active regardless of the season. KEY WORDS: Digital elevation model, Lineament, Landsat 8 OLI image, Vegetation index, Transient electromagnetic method, Crystalline basement. INTRODUCTION Groundwater in crystalline rocks mainly occurs in shallow weathered zones of limited narrow extent. Groundwater productivity in crystalline rocks is typically low and dependent on the thickness and width of the weathered and fractured crystalline bedrock (e.g., Wright 1992; Chilton and Foster 1995). Because fracture zones are mechanically weak and foci for weathering, they can store and 1 Department of Urban Management, Graduate School of Engi- neering, Kyoto University, Kyoto 615-8540, Japan. 2 Geology Department, Faculty of Sciences, Eduardo Mondlane University, Ave. Mozambique km 1.5, P.O. Box 257, Maputo, Mozambique. 3 Geology Department, Faculty of Science, Tanta University, Tanta 31527, Egypt. 4 To whom correspondence should be addressed; e-mail: koike.katsuaki.5x@kyoto-u.ac.jp Ó 2017 International Association for Mathematical Geosciences Natural Resources Research (Ó 2017) https://doi.org/10.1007/s11053-017-9360-5