Subsurface water exists below the surface of the soil in two zones: the unsaturated zone (zone of aeration) and the saturated zone (zone of saturation). The unsaturated zone includes soil water and the saturated zone includes groundwater. The water table separates these two zones. In the saturated zone, all pore spaces are filled with water, while in the unsaturated zone pores are partially filled. The unsaturated zone contains three sub-zones: the soil water zone where water is immediately available to plants, the intermediate zone, and the capillary fringe where water rises through capillary action.

1. SUB SURFACE
WATER
• Water in a soil mantle is called as sub surface water.
• Water beneath the surface can essentially be divided into
two zones
• the unsaturated zone (also known as the "zone of aeration")
which includes soil water zone,
• The zone of saturation which includes ground water.

2. • Sometimes, especially during times of high rainfall, these pore
spaces are filled with water.
• The water table divides the zone of aeration from the zone of
saturation.
• In the saturation zone, all the pores of soil are filled with
water.
• In the aeration zone, soil pores are partially saturated with
water.

3. • The aeration zone has 3 sub-zones.
i) Soil water zone
ii)Intermediate zone
Iii) Capillary fringe
SOIL WATER ZONE:
• Soil water is held in the pore spaces between particles
of soil.
• Soil water is the water that is immediately available
to plants.
• This water can be removed by air drying or by plant
absorption, but cannot be removed by gravity.

4. • Plants extract this water through their roots until the soil
capillary force (force holding water to the particle) is equal
to the extractive force of the plant root.
• At this point the plant cannot pull water from the plant-
rooting zone and it wilts (called the wilting point).
• The amount of water held in the soil after excess water has
drained is called the field capacity of the soil.

5. INTERMEDIATE ZONE:
•This is the layer that is available next to the soil water zone.
•It lies in between the soil water zone and the capillary zone.

6. CAPILLARY
ZONE:• The capillary fringe is the subsurface layer in which
groundwater seeps up from a water table by capillary
action to fill pores.
• Pores at the base of the capillary fringe are filled with
water due to tension saturation.

7. • This saturated portion of the capillary fringe is less than total
capillary rise because of the presence of a mix in pore size.
• If pore size is small and relatively uniform, it is possible that
soils can be completely saturated with water for several feet
above the water table.
• Alternately, the saturated portion will extend only a few
inches
above the water table when pore size is large.