Water Cycle

The water cycle is an underutilized yet powerful gateway and passport for getting in touch with nature. | Florida’s cycle Weather | Wet season | Dry season | Endless summer | Waiting for fall | Coolish winter | Spring drought | Hydrologic holidays

Intro - Florida's Flawed Seasons

And How the Water Cycle Simplified the Math

By Robert V. Sobczak

Why chose the water cycle ...

Over the seasons for tracking the year?

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Florida has two meteorological seasons: a wet and a dry

Don't get me wrong: The four seasons are great. And let's also not forget, officially they are celestially defined by the position of the earth's tilt as it rotates around the sun even. That being said, we tend to think of them meteorologically the most, or in other words, in terms of the weather.

That's where the seasons and the calendar year for that matter fail us in Florida. For one, the meteorological seasons are skewed quite significantly from the normal continental norms. Summer-like weather lasts for six months, not three. And when fall weather will arrive is anyone's guess. As for winter the season, it's more accurately defined by a spattering of days. And spring? I'm not really sure other than the air is drier but it can get quite hot.

swamp cross section
Swamp's cycle of flood and drought

Using January as the start of the year in Florida is also a complete fail. (Talk about getting the New Year off on the wrong start!) Why? January is smack dab in the middle of Florida's dry season. How can we start a new year when the season still has another 4-5 months on the books? That's where the water year comes in handy. It starts in May when the water table bottoms out and the wet season is about to begin.

So the big solution calls for a two-pronged approach: We replace the water cycle with the seasons and aligning our new annual clock with May, not January, as the start of the new year. And here's the twist: we don't have to drop the seasons and calendar year completely. We keep them in the mix, too. It's not about replacing the old regime completely, it's about custom crafting it to fit into Florida's unique meteorologic mold.

The water year, wet season and dry season help us simplify the seasonal math.

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Tortoise and Hare of the Swamp
And why they both deserve participation trophies

South Florida’s water cycle …

Resembles the fable of the Tortoise and the Hare.

Rainfall is fast and evaporation is slow, but over a year they usually balance out.

Think of rainfall is the Hare.

Summer rains are drenching and drainage of the swamp’s flat landscape poor. That causes water to rise rapidly and stay there through the summer and into early fall. But come mid October the wet season ends.

That’s when the Hare falls asleep and the dry season begins.

The Hare sprints ahead from late May into early fall

Enter the slow and steady Tortoise:

Evapotranspiration is slow and steady worker – some would say inexorable. As dry season weeks turn into months and the Tortoise marches on, by some point in the winter and definitely by spring pretty much all the water in the swamp is gone. Or in other words, drought …

And yes, wildfires, too.

Come spring the Tortoise catches up

But not so fast.

All it takes is one big rainstorm for the Hare to wake up, hurdle the Tortoise and sprint ahead out of sight, but not for long. Unlike the real fable of the Tortoise and the Hare, south Florida’s annual race called the water cycle has no beginning or end. Or in more scientific terms: The swamp is a flood and fire adapted ecosystem. Every square inch of flora and fauna depend on a goldilocks dosage and return interval of flood and fire to maintain the health of the swamp mosaic.

And the winner is …

Moral of the story:

The Tortoise and Hare are both winners. Participation trophies for both!

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Tidbit: The south Florida rainy season lasts from mid May to mid October, or about 5 months.

Water Years 2021/2022 in Review
A brief comparison of the past two years

1. Water Year 2021 (May 1, 2020 to April 30, 2021)

Water Year 2021 classified as above average in terms or rainfall, recording 46 and 14 inches of wet and dry season rainfall, respectively, for a total of 60 inches.  The summer wet season started early with a June-like rain total in May (8 inches) and ended late with above average rains in October and a surprise storm in November.  Of note, the early start was not enough, or rather in time, to prevent a destructive incineration of an archipelago of hardwood hammocks in the southeast Corner of Big Cypress National Preserve called the Moon Fish Wildfire.  Within a week of the fire ending the May rains swept through.  Near normal rainfall persisted for core four months of the summer wet season (June through September) and were supplemented by a “wet season” like October.  But the real exclamation point came in November in the form of Tropical Storm Eta, filling the Everglades and Big Cypress Swamp to levels last seen in September 2017 from Hurricane Irma, only shifted forward two months to a time when water levels are usually well past their October peak. 

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The late season highwater stand set the stage for or prolonged and steady winter recession that proved to be a boon to wading bird communities in terms of foraging and nesting.  Despite expectations of a wet dry season from the bumper crop of summer and late fall rain, the Big Cypress Swamp dropped into deep drought by April’s end.  Although no similar wildfires occurred, Water Year 2021 proved an important restoration point:  No matter how wet the wet season or the beginning of the dry season, without timely April and May rains the Big Cypress Swamp is especially prone to dropping into deep, unnatural drought due to perimeter and interior canals that stifle the spread of sheet flow and hasten its spring demise. 

2. Water Year 2022 (May 1, 2021 to April 30, 2022)

Despite the previous year’s bountiful rains, Water Year 2022 took started slow thank to subpar rains in May – extending drought conditions into June and even July in some area.  However, the four core seasons of the summer wet season (June through September) and October all charted in with average rainfall.  For a second year in a row, November provided an unexpected boost with twice its normal rainfall amount. Again, despite the surplus of water at the dry season’s start, the Big Cypress Swamp was poised to drop into deep spring drought, imperiling the habits that so vitally depend on natural fire breaks staying wet, when a string of continental fronts at the middle and end of April and start of May boosted the water table just when it needed it most.  South Florida received over 10 inches less annual rainfall and 4 inches less dry season rain than the prior year, but it is as much an issue of timing as it is the total amount. Water Year 2021 classified as low normal in terms or rainfall, recording 36 and 12 inches of wet and dry season rainfall, respectively, for an annual total of 48 inches. 

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Did You Know: Up north on the continent, the water year starts October 1st and ends September 30th in most areas.

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Start of Water Year?
Not to be confused with the "calendar" year

The calendar year isn’t so much “wrong,” as it has the wrong start date — at least from the perspective of a water drop. Can you guess what day the new water year starts in south Florida? Hint: Think of it as the water cycle’s birthday.

a. January 1st

b. November 1st

c. June 1st

d. May 1st

e. February 29th

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Read more to find out the answer

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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.