Sam Jaffa of Parkton uses well water, so he pays attention to rainfall statistics. He wonders: "Why is precipitation measured on a calendar-year basis? I suggest it should be a rolling 12-month basis. The surplus which may be built up ... does not magically disappear come Jan. 1." True. But droughts and surpluses can extend beyond a rolling 12-month window, too. There is no official yardstick. The calendar year is just one option. Where rainfall is critical, people can invent their own.