<P> Infiltration is the process by which water on the ground surface enters the soil . Infiltration rate in soil science is a measure of the rate at which soil is able to absorb rainfall or irrigation . It is measured in inches per hour or millimeters per hour . The rate decreases as the soil becomes saturated . If the precipitation rate exceeds the infiltration rate, runoff will usually occur unless there is some physical barrier . It is related to the saturated hydraulic conductivity of the near - surface soil . The rate of infiltration can be measured using an infiltrometer . </P> <P> Infiltration is caused by two forces: gravity and capillary action . While smaller pores offer greater resistance to gravity, very small pores pull water through capillary action in addition to and even against the force of gravity . </P>

What is the role of infiltration in the water cycle