Preliminary hydrogeophysical investigation at the 10th of Ramadan City, Egypt, by 1D and 2D inversion of VES data

Abstract

ABSTRACTElectrical resistivity survey in the form of vertical electrical sounding was conducted at the 10th of Ramadan City, Egypt, to analyse subsurface lithology distribution and the inter‐relation between the possible infiltrated wastewater from oxidation ponds and the surface seepage emerged at the city centre. Special interest was paid for tracing the low‐resistivity clayey layer, which can act as a barrier against surface water percolation and as a low permeable zone to form local perched water system. Vertical electrical sounding data by Schlumberger electrode configuration were taken at 17 stations along a line extended from the city centre to the oxidation ponds used for wastewater treatment. The data were inverted by using 1D and 2D inversion schemes to construct geoelectrical cross section along the surveyed line. The geoelectrical layers were interpreted principally in terms of lithology and water content by correlation with borehole information. From the obtained results, four layers were identified in the subsurface medium. The upper three layers are located above the regional water table, whereas the fourth one was interpreted to be fully water saturated. The second layer from the surface is of great importance as it is the low‐resistivity clayey layer. This layer is discontinuous along the survey line. Downward infiltration of wastewater from the oxidation ponds is possible especially at the pond No. 2 as the clayey layer was interpreted not to exist at the site. The infiltrated wastewater from the oxidation ponds was interpreted not to be the cause of the surface seepage emerged at the city centre because the clayey layer dips toward opposite direction. The probable sources of the seepage were considered the local surface infiltration from excess irrigation water in the nearby cultivated land and/or leakage from the underground water utilities in the city centre.