Effects on Runoff and Infiltration

Different intensities, or temporal distributions can have dramatically different effects on runoff and infiltration within the watershed.  You can think of the runoff on the watershed much like pouring water on a sponge.  If water is poured quickly (high intensity) then there is not time for the sponge to absorb much and most of it will be runoff.  On the other hand if water is slowly poured or dripped onto the sponge (low intensity) then most of it will be absorbed and little will be runoff.

The following animation illustrates the effects of infiltration, or losses (these are losses to surface runoff but are actually sources to groundwater) and runoff for a high (short duration), medium, and low (long duration) intensity storm.  For each case the total rainfall depth is the same, and equals the sum of the losses and runoff, but the different intensities alter the separate volumes of losses and runoff significantly.