Do all rivers flow to the seas and are all tidal waters salty? And what side of the fence is brackish water on?

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.

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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.


Florida’s biggest stream?
Hint: It's bigger than the Mississippi

Florida is famous for its abundance of water. Lake Okeechobee is fed from the Kissimmee and spans as far as the eye can see, the pre-drainage Everglades spread its sheet flow from coast to coast, the headwaters of the Apalachicola reach north of Atlanta, the Suwannee River is feed from north of Atlanta and the St. Johns River famously flows north.

Can you guess Florida’s biggest stream?

a. Apalachicola River

b. The Everglades (and Big Cypress Swamp)

c. St. Johns River

d. Gulf Stream

e. Lake Okeechobee

f. Suwanee River (and Okefenokee Swamp)

g. Floridian Aquifer (and springs)

Read More” to find out the answer

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Florida’s biggest stream
Hint: It's salty

What’s the biggest stream in south Florida?

Answer: The Gulf Stream.

The Gulf Stream is an awesome force

It flows at the mind dizzying rate of 30,000,000,000 gallons per second. Or in more normal stream units, around 4,000,000,000 cubic feet per second (cfs). If those numbers don’t register in your mind, don’t feel bad – join the club. They are too big to conceptualize as isolated numbers. Instead, consider them relative to south Florida’s biggest flow gate – the S79 W. P. Franklin Dam and Lock along the Caloosahatchee River. It peaked at a weekly flow rate of around 25,000 during the week of Tropical Storm Fay (in 2008), and is currently at just under 2,000 cfs.

That’s where our Lake Okeechobulator comes in handy.

With a few quick clicks of its buttons, it’s telling me that if we were able to catch the entire Gulf Stream by plunking a giant imaginary bucket into the Straights of Florida (from Cuba to the Keys), it would fill up one full Lake Okeechobee volume – 5.5 million acre feet – every minute. That adds up to 1,440 full Lake Okeechobees every day. So next time you’re out on Lake Okeechobee, staring out at water as far as the eye can see — don’t forget it’s a drop in the can for the Gulf Stream, accounting for only 33 seconds worth of water passing through the Florida Straights.


Old and New Everglades
How the past informs the future

This image is oldie …

But a goodie.

Pre and Post Drainage Everglades

I‘d always seen the images of the pre and post drainage Everglades side by side, and with all the looking back in forth it inspired me to superimpose them overtop of each other and toggle them back and forth. In a nutshell, there’s no going back to the pre-drainage. But that doesn’t mean we simply ignore the pre-drainage system. Understanding it helps us frame the possibilities and limitations of modern-day water management and restoration efforts. Also, the new mantra in the Everglades isn’t about looking into the past, but ahead into the future. Increasing attenuated water flows across the landscape is our best bet locally for battling back and keeping a balance with sea level rise.

One big caveat about this animated map: It doesn’t get the Big Cypress right. For one it cuts it in half and two, it doesn’t properly show the flows. Sounds like a new project. Stay tuned!