Soil Water Relationship
Soil water relationship in irrigation
- Soil mass is generally a 3-phase system composed of soil Solids, Water, and Air.
- The soil can be completely dry or completely saturated, in that condition soil is represented by the 2-phase system.
Simple Definition in the Phase system:
Ws = Weight of Solids
Ww = Weight of water
W = Total weight of Soil
W= Ws + Ww
Vs = Volume of Solids
Vw= Volume of water.
Va = Volume of air
Vv = Volume of Voids
Vv = Va + Vw
V= Volume of Soil
V= Vv + Vs
V= Va + Vs + Vw
1. Water Content (
):
The minimum value of water content is Zero (0) and there is no upper limit.
- The water content of the fine-grained soil is more than that of Coarse-grained Soil.
- Clay has the negative charge on its surface, to this -ve charge water dipole get attached, thus the retention capacity of water is more in the fine-grained soil.
2. Void Ratio (e):
- e>0: Since soil has to contain some voids, but there is no upper limit to void volume.
- The individual void sizes are larger in the coarse-grained soil, but the void ratio of fine-grained soil is generally larger than that in the coarse-grained soil.
e of clay > 0.8
0.5 < e of sand <0.7
3. Porosity (
):
0 < < 1
4. Degree of Saturation (S):
S=0: Dry Condition.
S=1: Saturated Condition