Characterization of multi-aquifer systems in arid regions by geological and multidisciplinary geophysical approaches: a case study of Helwan springs area, Egypt

Abstract Helwan area, the southern suburb of Cairo, embraces several unique sulfur and mineral water springs that flow 24 hours a day. This work was conducted at the springs area to pinpoint the currrent situation of water-bearing formations, their spatial distribution, structural controls, and potential feeding source(s). In this regard, a geological and multimethod geophysical approach, including vertical electrical soundings, transient electromagnetics, audiomagnetotellurics, and electrical resistivity tomography was applied. Four groundwater aquifers could be characterized, where the fractured limestone of the Eocene age is the main aquifer. Analysis of satellite images and gravity data revealed three fault sets, with a major trend of NW–SE orientation. Moreover, three streams including the Wadi Garawi, Wadi Hof, and Wadi Abu Ghraqid draining towards the springs area, were outlined. The springs are controlled by the dominant geological and hydrogeological conditions and the feeding sources include surface seepage, rainwater, as well as water from the deep aquifer along the fault planes. Hydrochemical, bacteriological, and isotope studies are currently being undertaken to assess the origin and water quality, as well as the proper methods for sustainable human uses of these water resources.