Hydrological Cycle
¥85% of water
vapor in atmosphere evaporates from oceans.
¥About 40% of
precipitation that falls over land is runoff, 
and the other
60% is transpired/evaporated.
and the other
60% is transpired/evaporated.¥Water vapor
molecules reside in atmosphere for about one week on average
week on averageAhrens
Fig. 4.1
85%
15%
40%
60%
Ultimate source of
all fresh water