Groundwater potentiality mapping: A case study in Baba and Sidri watersheds, South Sinai, Egypt

Abstract

Groundwater potential zone (GWPZ) mapping is a multi-parameters approach that can assess the groundwater potentiality in mountainous terrain and coastal areas. This approach utilizes the geomorphology, lithology, rainfall, structure lineaments density, drainage density and slope which are the major effective factors controlling the groundwater potentiality. Primarily, these factors are prepared in the form of thematic layers using GIS technique, and then assigned different weights for these thematic layers using Analytical Hierarchy Process (AHP) technique to explore the GWPZ. This GWPZ is generated by the linear weighted sequence of all the prepared thematic layers. The moderate GWPZ (41.8%) sites are located in the main Wadi channels and alluvial fan at western portion; whereas, the high GWPZ (29.8%) concentrates in Homaier depression at the eastern region. Vertical electrical soundings (VES) and time-domain electromagnetic soundings (TEM) measurements have been achieved at high GWPZ to estimate depth and thickness of both saturated and unsaturated areas with water. This geophysical investigation has been done to confirm and support the effectiveness of applied factors of GWPZ mapping. The findings of these measurements are validated by standardizing the measured electrical resistivity values with the sequential layering layout and data records for five wells drilled at the locations of the geophysical soundings. VES and TEM data show the existence of moderately thick adjacent aquifers, covered with a dry area of different thicknesses (18–50 m). The aquifer units with thickness ranging from 43 to 71 m has resistivity values of 22–50 Ω m which is an indicator of freshwater content.