Vertical Distribution of Groundwater:
Division of Subsurface water
The subsurface occurrence of water may be divided into zones of aeration and the zone of saturation.
Zone of Aeration:
The zone of aeration is also known as the vadose water zone, unsaturated area or zone of suspended water.
The zone of aeration is the region between the earth's surface and the water table.
The zone in which gaps of soil and rocks are filled with partially by water and partially by air.
Zone of Aeration( vadose water) further subdivided in to three groups:
ⅰ) Soil-Water Zone
ⅱ) Intermediate Vadose Zone
ⅲ) Capillary Zone
1. Soil-Wate Zone:
Water in the soil-water zone exists at less than saturation except temporarily when excessive water reaches the ground surface as from rainfall or irrigation.
The zone extends from ground surface to the major root zone.
The zone thickness varies with soil type and vegetation.
2. Intermediate vadose water zone:
The intermediate vadose zone extends from the lower edge of the soil-water zone to the upper limit of the capillary zone.
Intermediate vadose zone thickness varies from 0 to 100m.
3. Capillary Zone:
Capillary zone also known as Capillary Fringe.
The capillary zone extends from the bottom edge of the intermediate zone to the upper edge of the saturated zone.
The thickness of the capillary zone depends on the properties of soil and also on the homogeneity of the soil.
The depth of capillary zone is varying from few centimeters to few meters.
In capillary zone, all the pores are filled with water. However, we cannot draw water by inserting a well up to that depth. This is because of the negative pressure developed at this zone due to surface tension effect.
Zone of Saturation:
The zone of saturation extends from the upper surface of saturation down to underlying impermeable rock.
The zone in which all pores of soil are filled with water.
The top surface of the zone of saturation or groundwater is known as Phreatic surface.
The Phreatic surface is also known as water table.
Groundwater is present in the zone of saturation.
Groundwater is also known as phreatic water.