Shallow geophysical techniques to investigate the groundwater table at the Great Pyramids of Giza, Egypt

Sharafeldin M Sharafeldin,Hakan Karsli,Nilgun Sayil,Mohamed A S Youssef,Zein E Diab,Khalid S Essa

doi:10.5194/gi-8-29-2019

Abstract

Abstract. The near-surface groundwater aquifer that threatened the Great Pyramids of Giza, Egypt, was investigated using integrated geophysical surveys. A total of 10 electrical resistivity imaging, 26 shallow seismic refraction, and 19 ground-penetrating radar surveys were conducted in the Giza Plateau. Collected data for each method were evaluated by state-of-the art processing and modeling techniques. A three-layer model depicts the subsurface layers and better delineates the groundwater aquifer and water table elevation. The resistivity of the aquifer layer and seismic velocity vary between 40 and 80 Ωm and between 1500 and 2500 m s−1, respectively. The average water table elevation is about +15 m, which is safe for the Great Sphinx, but it is still subjected to potential hazards from the Nazlet El-Samman suburb where the water table elevation reaches 17 m. A shallower water table at the Valley Temple and the tomb of Queen Khentkawes, with a low topographic relief, represents severe hazards. It can be concluded that a perched groundwater table is detected in the elevated topography to the west and southwest that might be due to runoff and capillary seepage.

Highlights

In recent years, the 4500-year-old Great Pyramids of Giza (GPG), Cheops (Khufu), Chephren (Khafre), Menkaure, and the Great Sphinx have been threatened by a rising groundwater table resulting from water leakage from the suburbs, irrigation canals, and mass urbanization surrounding the GPG
The integrated interpretation of ERT, seismic refraction (SSR), and ground-penetrating radar (GPR) surveys was performed at the Great Pyramids of Giza site to successfully investigate the groundwater aquifer and water table elevation and assist hazard mitigation
The third layer shows a high velocity at 2800–3800 m s−1 and a resistivity range of 40–100 m correlated with limestone and dolomite in the saturated zone

Summary

Introduction

The 4500-year-old Great Pyramids of Giza (GPG), Cheops (Khufu), Chephren (Khafre), Menkaure, and the Great Sphinx have been threatened by a rising groundwater table resulting from water leakage from the suburbs, irrigation canals, and mass urbanization surrounding the GPG. This problem promoted the need to use nondestructive near-surface geophysical techniques integrated with available borehole hydrogeological data to investigate and characterize groundwater occurrences in the GPG. The recharge of the aquifer below the Sphinx area occurred mainly through water system leakage, irrigation, and mass urbanization (AECOM, 2010; El-Arabi et al, 2013)

Methods

Results

Discussion

Conclusion