Why is soil moisture such a critical factor in ground resistivity?

Soil moisture plays a vital role in ground resistivity primarily because it directly affects the electrical conductivity of the soil. When soil moisture content increases, the ions present in the water enhance the soil's ability to conduct electricity. Wet soil typically has a lower resistivity compared to dry soil, allowing electrical currents to flow more easily through it. This conductance is crucial for effective grounding systems in lightning protection, as a proper grounding system relies on low resistivity to safely dissipate lightning strikes into the ground.

In contrast, while soil moisture may influence factors like the chemical composition or drainage capabilities of the soil, these aspects are secondary to its impact on electrical conductivity. Temperature changes due to moisture levels can affect resistance as well, but they are not the primary reason for changes in ground resistivity. Understanding these relationships assists in designing effective lightning protection systems that rely on efficient grounding.