estuaries

Intro - More than Brackish

By Robert V. Sobczak

We all know the standard definition:

Estuaries are where fresh and salt waters mix.

animation estuary

Oh, the naivete!

Yes, estuaries are brackish, but they are so much more (very much more) than that. And increasingly they are imperiled by forces on both sides. Salty waters are moving in, more and more frequently than ever before thanks to a changing climate. And don't take my word for it. Just ask any fisherman whose ever fished along the freshwater fringe of the Gulf Coast. Not trust a scientist, shame on the scientist. Not trust a old timer angler, shame on you. And then there's the whole "freshwater watershed" side of how estuaries are being similarly stressed. Whether it's alteration of overland flows or degradation of its water quality, estuaries are as much a special place as they are a battle ground for forces hitting them on both sides.

Florida's Coastal Names

Coastal water bodies and beaches deserve our attention more than every. They are nature's canary in the coalmine.

Recent Blog Posts

Mississippi South Florida Style
The Lake Okeechobee measuring cup

Hydrology numbers get big, confusing …

And obtuse.

Mississippi River’s annual discharged measured in Okeechobees

Millions of gallons per day, acre feet per year, cubic feet per second … the list goes on. The fact is, at some point it all just turns into a jumble of numbers. That’s where Lake Okeechobee comes in handy as a giant measuring spoon. Did you know that each year on average 100 Lake Okeechobee volumes worth of water discharges into the Gulf of Mexico from the Mississippi River. I could have said 400 million acre-feet of water, or some gargantuan number in gallons or cubic feet. But if you’ve ever stood on the levee of Lake Okeechobee and looked out at the expanse, it kind of puts it in perspective: The Mississippi discharges about one hundred Okeechobees into the Gulf each year. That’s one mighty river!

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Tidbit: The Mississippi River discharged over 160 Okeechobees into the Gulf during the flood year of 2000, and just over 60 during the drought years of 2006 and 2012.

animation lake canoe

Caloosahatchee meets Mississippi
And how the two compare

The Caloosahatchee is …

The king of freshwater flows in South Florida.

Comparison of annual freshwater discharge from the Caloosahatchee (red), Apalachicola (dark green) and Mississippi River (light green)

Currently flowing at around 5,000 cubic feet per second (cfs), it’s the single highest flowing point in the Greater Everglades. But not only is that flow rate dwarfed by the 17,000 cfs discharging out the mainstem of north Florida’s Apalachicola River, both are dwarfed by the nearly 700,000 cfs discharging from the Mississippi River into the Gulf. How much is 700,000 cfs … in more relatable lay audience terms? Answer: Every year, on average, the Mississippi River discharges about 100 Lake Okeechobee’s worth of freshwater into the Gulf. Note: The calculation is based on the assumption of a Lake stand of 15 ft above seas level, or the top of the Lake’s interior-levee littoral zone at which time its water volume is around 4 million acre feet. On average, the Caloosahatchee discharges about a quarter Lake Okeechobee volume worth of freshwater into the Gulf per year. Of course in the case of both, it’s just not water quantity — water quality matters, too, if not the most.

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Tidbit: The Mississippi starts its 2,552 mile journey to the Gulf of Mexico at Minnesota’s Lake Itasca, as photographed in 2014.

Lake not the blame (this time)
Closed gate but rising flows downstream?

With The Lake near its annual low …

And the Kissimmee River at a similar ebb:

A semi-complicated hydrograph summarizing some key indices for Lake Okeechobee over the past two years, including rainfall, lake stage, inflows from the Kissimmee River and discharge through the S-79. See the complete cheatsheet for the lake.

Why then have discharges down the Caloosahatchee River’s S-79 into the Estuary suddenly spiked to over 5,000 cfs, which in layman terms is around 34 Fenway Parks filled to the top of the 37.5 foot high Green Monster every day? Answer: Blame all the rain in the Caloosahatchee Watershed, not the Lake. The S-77 which controls Lake flows into the C-43 are closed, and is therefore recording no flow.

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Tidbit: At 13 feet above sea level, Lake Okeechobee is about 8 feet below the level it naturally overflowed its southern shore into the Everglades prior to drainage.

Swamp to estuary

The Big Cypress is a multi-dimensional swamp.

In addition to using the rainwater for itself …
 

Talk about multi-tasking!

It also feeds it downstream into the mangrove coast.

Spoon-fed estuary

An estuary’s best friend …

Is an unpolluted and intact watershed upstream.

Can you see the cypress strand
in the foreground and the mangrove
estuary in the distance,
looking south?

 The swamp is ever so happy to share and send its freshwater south.