The Infiltration of Water Below Ground and the Concept of an Aquifer - Hydrogeology: Objectives, Methods, Applications - page 32

particle absorbent bristles soil solution

S: plant suction

F: retention

P: weight

Figure 12 Types of water within a solid material (from Gobat et al ., 1998).

The water fi lling large pores is subject to the force of gravity, and
therefore fl ows downward. Water in small pores, on the other hand, while
still subject to the force of gravity, is more infl uenced by capillary forces.
Water present at shallow depths is subject to evaporation, and the
zero-fl ux plane (Figure 13) separates water returning to the atmosphere as
a gas from water fl owing downwards as a liquid towards the water table

Gas
transfer

Liquid
transfer

Figure 13 Distribution of water in a soil profi le.