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1.01 X 10~3

Source: A. Verrjuitt, 1982, Theory of groundwater How, 2d ed. (Macmillan Publishing Co.).

Source: A. Verrjuitt, 1982, Theory of groundwater How, 2d ed. (Macmillan Publishing Co.).

of the relationship between volumetric water content and the negative pressure head (height above the water table or capillary pressure).

For materials with relatively uniform particle size and large pores, the water content decreases abruptly once the air-entry value is reached. These materials have a well-defined capillary fringe. For well-graded materials and materials with fine pores, the water content decreases more gradually and has a less well-defined capillary fringe.

At a large capillary pressure, the volumetric water content tends towards a constant value because the forces of adhesion and cohesion approach zero. The volumetric water content at this state is equal to the specific retention. The specific retention is then the amount of water retained against the force of gravity compared to the total volume of the soil when the water from the pore spaces of an un-confined aquifer is drained and the groundwater table is lowered.

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