<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 most often measured in millimetres per hour or inches 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>
what happens to water that infiltrates the soil if it is not absorbed by the roots of plants
runoff