New “water year” approaches
Why water year trumps calendar year

The start of May marks the beginning …

Of a new water year.

Why May?  Here’s the reasons:

  • In south Florida that’s when water levels are normally at their low point.
  • May through October 31st is the rainy half of the year
  • Summer showers usually start in May.
  • To confuse everyone.

Actually, using the water year helps simplify the math. The six month summer span (May-Oct) marks our reliably rainy half of the year whereas the six month winter span (Nov-Apr) marks the time when rains are the exception, not the rule.  October and May are actually “shoulder season” months  They can go either way — wet or dry, and sometimes both. But in terms of hydro bookkeeping, organizing the water year by equal 6-month wet and 6-month dry seasons avoids having the start the year in the middle of the dry season (January) and ending the year on two orphaned months (November and December) of the following water year.

Water Year Time Piece

One more point of confusion:

Some people say we’re entering the 2022 (i.e. not the 2023) water year.  While on the one hand, that sort of makes intuitive sense, for the reason that the bulk of the coming water year both in terms of months (8 of the 12) and rainfall (43 inches of the 55 inch annual total), the convention is to number the water year according to the calendar year it ended. And if you think about it, that does make sense: This year’s graduates will be “Class of 2022,” not 2021.

Nobody said the water cycle was always easy, but using the water year definitely helps us simplify the hydrologic math, and puts us in tune with the water cycle in a way that the calendar year falls short.

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