unsaturatedzone
Unsaturated zone, also called the vadose zone, is the part of the subsurface between the land surface and the water table where pore spaces contain both air and water. Its properties depend on soil texture, structure, and organic matter, and moisture content varies with depth, rainfall, and vegetation.
Water in this zone is held by capillary and gravitational forces and moves slowly through unsaturated flow.
Functions: stores plant-available water, drives groundwater recharge, and acts as a natural filter and biogeochemical reactor
Measurement and relevance: engineers and hydrologists assess soil moisture with tensiometers, time-domain reflectometry, or neutron probes;