Classification Soil Water
All soils are permeable materials, water being free to flow through the interconnected pores between the solid particles. The pressure of the pore water is measured relative to atmospheric pressure and the level at which the pressure is atmospheric ( i.e. zero) is defined as the water table (WT) or the phreatic surface. Below the water table the soil is assumed to be fully saturated, although it is likely that, due to the presence of small volumes of entrapped air, the degree of saturation will be marginally below 100%.
Water presence in the voids of soil mass is called soil water. It can be classified in several ways:
1 Broad classification:
1. Free water
2. Held water
a. Structural water b. Adsorbed water c. Capillary water
2 Classification on phenomenological basis
1. Ground water
2. Capillary water
3. Adsorbed water
4. Infiltrated water
3 Classification on structural aspect
1. Pore water
2. Solvate water
3. Adsorbed water
4. Structural water
Water is free to move through a soil mass under the influence of gravity.
It is the part of water held in the soil pores by some force existing within the pores.
Such water is not free to move under gravitational force.
Adsorbed water is that water which the soil particles freely adsorb from atmosphere by physical force of attraction and held by force of adhesion.
Water is the vicinity of soil particles subjected to an attractive force basically consists of two components.
i) Attraction of bipolar water to be electrical charged soil.
ii) Attraction of dipolar water to the action in the double layer, cation in turn attract to the particles.
It is the water chemically combined in the crystal structure of the soil mineral. Structural water cannot be separated or removed and also not removed by oven drying at 105-110 o c.It can be destroyed at higher temperature which will destroy the crystal structure.
Infiltrated water is the portion of surface precipitation which soaks into ground,moving downwards through air containing zones.
It is cable of moving under hydrodynamic forces unless restricted in its free movement such as when entrapped between air bubbles or retention by capillary forces.
Gravitational and capillary water are the two types of pore water.
The water which forms a hydration shell around soil grains is solvate water. it is subjected to polar electrostatic and binding forces.
Subsurface water that fills the voids continuously and is subjected to no force other than gravity is known as gravitational water.