Mapping water seepage from Lake Nasser, Egypt, using the VLF-EM method: a case study

In order to map the spatial distribution of water seepage from the Nasser Lake to its adjacent shallow Nubian sandstone aquifer, a geophysical survey was carried out at a seismically active area called Khor El Ramlah-west that contains the Khor El Ramlah regional fault. The survey comprised nine, roughly E-W, very-low-frequency electromagnetics (VLF-EM) traverse profiles and three N-S longitudinal profiles. Qualitative interpretation of the VLF-EM data was carried out using Fraser and Karous-Hjelt filters. Quantitative interpretation of the data was done with a 2D code that performs the inversion of the tipper data. The resulted 2D inversion models revealed low resistivity zones that were interpreted as correlated (1) to sandstone formation saturated with water from seepage and (2) to a NW-SE fault that may represent a preferential path for the water flow from the lake to the onshore aquifer.