Infiltration - opengeology.in

Infiltration is the process by which water reaching the ground surface enters the soil. Infiltration rate is a measure at which soil is able to absorb rainfall. It is measured in mm per hour.

Infiltration is governed by two forces Gravity and Capillary action. Smaller pores offer greater resistance to Gravity, very small pores pull water through capillary action in addition to and against the force of gravity.

Factors affecting infiltration :-

Soil texture and structure : Coarse soil encourages high infiltration.
Vegetation type and cover : Vegetation creates more porous soil which encourages infiltration.
Soil moisture : Dry soil have high infiltration rate, with increase of soil moisture the infiltration rate decreases.
Top soil layer : Top soil rendered porous by insects and burrowing animal encourage high infiltration.

Infiltration capacity of soil :

If a soil is initially dry, the infiltration capacity is high. As the soil moisture content increases, the infiltration capacity decreases. Eventually the infiltration capacity reaches almost a constant value determined by unsaturated permeability of the soil.

The decay of infiltration with saturation of soil is given by an exponential curve. As per Horton, the infiltration rete after time t may by given by the following equation –

f_t = f_e + (f_o – f_e) e ^-kt

where, f_t = infiltration rate at time t

f_o = initial infiltration rate or maximum infiltration rate

f_e = the constatnt or equilibrium infiltration rate after the soil saturation or minimum infiltration rate

k = decay constant specific to soil