S12D at 200

Rain Or Shine Report for Apr 30

Did you ever wonder what 200 cubic feet per second looks like?

Me too.

Here’s a short film showing the S12D during such a momentus occassion, just last week.

S12D is the easternmost S12 structure used to release water into downstream Everglades National Park.

Of the four S12 structures, S12D releases water at the highest rate and for the longest duration during a typical year.

Click here to view a historical calendar of flows through the S12D that goes back in time through the decades. Don’t be daunted by the figure: it reads like a book, from top to bottom (for years) and from left to right (for months of the year).

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Or you can just read the one I posted below.

OK … maybe it doesn’t read exactly like a book . . . but you know what I mean.

Or click here for a similar historical flow calendar for the S12A (the westernmost S12 structure) for a cross comparison. That’s where the Third Gator was from a couple of posts ago.

Why the difference?

S12D is closer to Shark River Slough — that means that it can handle more water.

Also click here to view a historical calendar of the combined flow rate through all the S12s over the past couple decades.

It shows very clearly how last year was such a low flow year: Combined S12 discharge didn’t even make it over 1000 cfs at any point in the summer.

Compare the previous year (2006) when it peaked out at just over 2,000 cfs for about a month, and the year before that (2005) when combined S12 discharges exceeded 3,000 cfs for 4 consecutive months.

But don’t forget that the true hydrologic currency of flow in south Florida is acre-feet.

Cubic feet per second come and go — sort of like the hourly value of the DOW … but converting to acre-feet per year allows you to compare oranges to oranges — as we say in Florida — and you can really simplify the math in comparing one structure to the next, or back in time.

Below is a such a graph for S12 , in our beloved acre-feet per year units … in millions of acre-feet per year to be exact.

What’s a “big flow year” for the S12s.

That would be a combined flow above 1 million acre feet.

That happened most recently in 2005, and before that in 1999. For all you “old timers” out there, around 2.4 million acre-feet passed through the S12s in 1995.

How big is 2.4 million acre-feet.

That’s enough to fill the Lake up from zero to the 11 ft mark.

Speaking of 11 ft …

The Lake has now been below that level for almost 420 days.

But back to the S12s.

What’s in store for 2008?

That’s anyone’s guess.

But that’s the great thing about the water cycle: You don’t have to guess.

You can watch it unfold as it happen.

I’ll go out on a limb and say it will probably be over 200 cfs but under 5,000 cfs.

Oh, did you mean in acre-feet.

I’ll go on the record with 1 million acre feet on the nose will pass through the S12s in 2008. But that’s just a wild guess, and you’ll have to give me plus-or-minus 100,000 acre-feet as a margin of error.
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It’s good to get projections out of the way early.
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That gives me an excuse to fall back on later:
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My prediction may not end up being the most accurate, but it was the earliest.

We still have May and June to go before they even open in earnest in July.
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Don’t forget to tune into next week’s installment of the Rain Or Shine Report, featuring an analysis of this year’s dry season rains — basin by basin and relative to dry seasons of recent and distant past.
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