“Rain, rain, go away. Come again some other day.” The problem of getting too little or too much rain is hardly new. The nursery rhyme that begins with those words originated in the days of Queen Elizabeth I, during the late 1500s. If only we could cause rain to fall in amounts and durations that suit our individual purposes, there probably would be no floods, no droughts, no ruined concerts, ball games or picnics. Nearly 500 years later and with all our technological advances, we still cannot control precipitation. What we can do is manage precipitation when it gets to earth.