Engineered fall

The dry season is here … finally!

How do I know?

Some look to the skies for the absence of clouds. Others go by the feel of cooler (or less warm) temperatures. Still others look for the signs of dry ground.

While each has its merits, they are subjective and uncertain to a degree:

  • The tropics stay open until November’s end,
  • Sloughs and strands remain under water (even if the pines have gone dry),
  • And cloudless skies can still torch with summer-style heat.

My hunt for the “case-closed-gate-shut” sign led me to the S12A.

It quite literally shuts (stopping the water) on November 1st of each year.

The S12A is the westernmost of the four famed water control structures that deliver inflows into the northern boundary of Everglades Nat’l Park.

(They are revamping another closer to Miami – by means of a one mile bridge – which will incrementally increase flows into the main channel of Shark River Slough over the coming years.)

As for now, the other three S12 structures are still open,

But they too will close as the dry season progresses in the months ahead.

It’s been a relatively small inflow year for the Park –

Around 350,000 acre feet of water has discharged through the four S12 structures this year to date. The annual average discharge over the past 10 years has been 650,000 acre feet. The big flow year of record was 2,300,000 acre feet in 1995. The most recent big flow year was 1,200,000 in 2005.

As a result, water depths in Shark River Slough fell about 8 inches below the normal early fall peak. Current stage is also about 8 inches below early November of last year, almost 2 feet below the late October peak of the record 1995 year, and a half foot higher than the drought summer of 2007.

The summer drought of 2007 was an interesting year.

The S12s delivered a measly 30,000 acre feet of water into the Park – which, in comparison, is less than the annual flow volume down the diminutive Turner River here in Big Cypress Nat’l Preserve. As a result, the glades stayed contained in the ridge and slough lowlands of the park all year.

That year, the question wasn’t so much when the dry season began,

But rather how the wet season never got started.

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