Infiltration is an important part if the cycle. About 1/3 of the water falling on normal vegetated land will infiltrate into the phreatic zone ("water table"). This provides baseline flow to streams, keeping streams flowing during dry periods. Another 1/3 will infiltrate into the vadose zone (unsaturated soil) but be drawn out again by evaporation and transpiration. The other third runs off into surface waters. Thus, infiltration both nourishes plant life and provides flow stability to surface streams.