## 2 Materials and Methodology
A relation can be established between aquifer lithology and the resistivity to map the geometry of sub-surface layers, provided that the rock mass is correlated with resistivity ranges [49] ([PERSON] et al., 2011). Resistivity method is also used to classify freshwater and saltwater horizons, groundwater quality [50; 51; 52; 53] and demarcate of fresh and saline water boundary [54; 55]. Figure 2: Schematic illustration of the VES technique and electrode arrangement for Schlumberger configuration. Based on the calibrated results (Figure 3), between resistivity modeled curve-30 and borehole lithology, a standard correlation of layers was prepared separately for lithologies listed in Table 2. This standardized correlation was then applied to all VES data points. The computed resistivity ranged from 20 to 90 \(\Omega\)-m, indicating aquifer for 17 polygons having fresh to saline water in the study area is presented in Table 2.  
Pumping Test: Depending on the nature/type of the aquifer, various techniques are applied to pumping data (time drawdown vs. time) to find the hydraulic parameters of the aquifer. These parameters are important for the prediction of the future availability of groundwater reserves [23; 56]. Aquifer parameters including hydraulic conductivity, transmissivity, and storativity are commonly applied in groundwater modeling [40; 57; 58] and these parameters are also estimated using the hydro-geophysical technique [16; 59; 60]. Permeability and formation factor can be estimated using empirical correlation [39; 61]. The method proposed [62] for estimating the transmissibility and storability of aquifers using specific well capacity. Aquifer characteristics and electrical parameters of the geoelectrical layers have been studied by many researchers [63; 64; 65; 9; 66]. extracted from drilled wells or test hole wells. It governs, along with other parameters, the flow of fluids and the migration of contaminants in the subsurface lithologies. Hydraulic conductivity is a measure of how easily water can pass through soil or rock: high values indicate permeable material through which water can pass easily and vice versa. The Lower Bari Doab (LBD) is part of the Indus Basin is very important for the characterization of hydraulic properties, fundamental for the assessment of the future availability of groundwater resources and precise management. To model the behavior of hydraulic conductivity in the aquifer, a grid consisting of 66 columns by 26 rows is overlaid on the area with a spacing of 5000 m, both in X- and Y-directions. For this purpose, test holes and water wells are used which had been drilled during different exploration stages by WAPDA. The pumping test data and the hydraulic characteristics of these water wells were also studied [31; 67; 68]. In addition to the pumping test data and subsequent results, laboratory hydraulic conductivity (Klab) comprising different subsurface materials from different depth intervals was also available from test holes located in the study area. Although not all intervals were sampled, a lithological description was available for different depths. A value of Klab from an identical lithology was assigned to intervals for which a measured hydraulic conductivity was not available. The values of the laboratory conductivity were lower than the conductivity obtained from the pumping test analysis data due to the obvious reason that the samples obtained from different depths were disturbed and their physical properties (porosity, packing, grain orientation) were also variable. The difference between the Klab and pumping test hydraulic conductivity values (Kpump) was adjusted to Klab by devising a mechanism [69; 70] to evaluate the conductivity (K). By taking the geometric mean, the conductivity values (Klab) beneath each test hole were averaged out, and thus a single value termed, individual laboratory conductivity, was assigned to an aquifer for an individual polygon.