# What is a good method to locate underground water for a well?

Resistivity is defined as the resistance to current flow as a result of an applied electrical potential. In geophysical surveys resistivity is determined as the electrical resistance per length of a unit cross section area (such as $\frac{\frac{o h m s}{m}}{m} ^ 2$. Resistivity of underground is a function of material type, porosity (void volume), water content, and concentration of dissolved impurities in the pore water. Generally, dry solids and rock have very high resistance to electrical flow whereas saturated (filled with water) underground has a relatively low resistance.