This lecture continues the ongoing exploration of surface geophysical methods in groundwater investigations. It emphasizes that when geological mapping is insufficient, geophysical methods such as electrical resistivity can provide crucial subsurface information, revealing details about aquifer depth, thickness, and quality. Electrical resistivity surveys, including the Wenner and Schlumberger arrays, help identify water-saturated zones and salinity by measuring variations in resistivity. It also covers the two main types of resistivity surveys: profiling for lateral changes and vertical electrical sounding (VES) for depth probing. The lecture concludes with an overview of electrical resistivity tomography (ERT) and its applications, such as imaging subsurface structures and assessing groundwater characteristics.