What does the term "interstitial water" refer to?

The term "interstitial water" specifically refers to the water that fills the spaces, or voids, between soil particles. In the context of soil science and geotechnical engineering, understanding interstitial water is crucial because it plays a significant role in the behavior of soils, including their strength, compressibility, and hydraulic conductivity.

Interstitial water influences the effective stress in soil mechanics, which is the stress that contributes to soil strength. This water is typically influenced by factors such as soil type, compaction, and saturation levels, affecting how the soil will respond under loads and during environmental changes like rainfall.

In contrast, the other definitions involve different aspects of water in relation to soil. For instance, the absorption of water by plant roots is more related to biological processes, while water that bonds with soil particles pertains to molecular interactions rather than the water's role in the soil structure. Similarly, while moisture content itself can be defined in various ways, interstitial water specifically denotes the water in the voids among soil particles, which is a more precise characterization.