## 5 Results and Discussion  
### Two-Dimensional Electrical Resistivity Tomography (2D-Ert)  
Eleven profiles were surveyed around the Osirion, with a total length of 360 m; six of them (P1-P6) were performed in the direction of NW-SE, while the other five profiles (P7-P11) are in the direction of NE-SW, forming a mis-like shape. The remaining three profiles, (P12-P14) are trending NW-SE. P12, P13, and P14 have lengths of 360 m, 140 m, and 73 m respectively, based on the accessibility of the profile places (Figure 4). The lithology and the thickness of the subsurface succession were determined in the 2D resistivity data; and the results were confirmed with the results of the available wells, which located on and near the surveyed profiles. Nine wells were available, with varying total depth from 63 to 103 m, and used for this purpose. Only two wells (W1 and W5) were used for comparison with the inverted ERT profiles because the well W1 is located directly on profile 10 and well W5 is very close to profile 1 (Figure 4).  
The interpretation of the 2D inverted resistivity profiles P1 and P10 after calibration, with the lithology were implemented. Using the conceptual knowledge from this calibration with well data, all the inverted resistivity profiles were interpreted (Figures 5-8). The depths to the water table of wells W1 and W5 are shown in Figures 5 and 7.  
Following the careful inspection of the ERT profiles, four distinct geoelectrical zones with varying resistivity values were recognized as the following:  
1. The first zone is characterized by high resistivity values (more than 2000 ohm.m), which are consistent with the surface wadi deposits at the site. This zone is mostly composed of gravel, sand, and silt deposits. The thickness of this zone varies progressively from 2.5 m to 18 m. In some locations, the resistivity values increase to be about 10,000 ohm.m, reflecting the presence of gravel deposits. This zone is recorded in most of the profiles except for profiles 13 and 14.
2. The second geoelectrical zone has moderate resistivity values ranging from 200 to 2000 ohm.m, which reflects a nature of medium sand deposits. It was constituted due to high currents suspended by the medium grain size of sands that invaded the gravels of the former zone, scouring it forming cuttings and remnants of medium sand.
3. The third geoelectric zone is characterized by low resistivity values (50 to 200 ohm.m). It was interpreted as muddy sand deposits. The formation of this zone is similar to the formation of the former zone. It was formed due to active currents suspended by muddy sand invading the wadi deposits zone, scouring it forming cuttings and remnants of muddy, sand-like roots within this zone. This zone is saturated with the groundwater as it was confirmed from the adjacent wells. The thickness of this zone is not uniform through all the profiles due to sedimentation processes. It varies from 6 m to 19 m.
4. The fourth geoelectric zone is characterized by very low resistivity values (less than 50 ohm.m). The maximum thickness of this zone is recorded in profiles 13 and 14, which correspond to the Nile River clay deposits near the cultivated lands. It is noticed that the thickness of this zone is increasing in the direction of the River Nile and decreasing in the direction of the limestone plateau. It was recorded as spots in the rest of the other profiles and may be expected to be bound deeper beneath all the recorded zones.  
It is crucial to inspect all of the resistivity profiles together as will be discussed later in 3D interpretation and the data of the available wells; the water table level in the study site varies from 5 m in some places to 14 m in other places.  
Figure 5: Interpreted 2D inverted resistivity model of profiles 1–4. According to the resistivity values, four difference geoelectric zones were recognized. These zones are: (1) wadi deposits, which are mainly composed of gravels, sands, and silts; (2) medium sand deposits; (3) muddy sand deposits; and (4) clay deposits.