Below the water table, all pores within the soil are completely filled with water. This region is called the zone of saturation, also known as the phreatic zone. The moisture within the soil is broken down into many different types. When water is moving through the larger pore spaces, it is called gravity water. Capillary water is the water located within the smaller pores.
Hygroscopic moisture is a thin layer of water adhering to grains of soil.
During a rain event, the water movement from the surface into the soil is known as infiltration. Once absorbed, the movement of this water through the soil is described as percolation. Infiltrated water moves through the larger pores as gravity water, and the smaller pores at the surface are filled with capillary water. The downward moving water also fills the smaller capillary pores as it percolates through the soil. This effect diminishes the amount of gravity water moving to deeper soil layers.