Here’s a historical overview …
Of discharge through all the S12s (A, B, C and D).
These are the four monolithic concrete structures you drive by on the Tamiami Trail between the midpoint of the Everglades (i.e. as demarked by the S-333 and the L-67) and the eastern entrance into Big Cypress National Preserve (i.e. also known as 40 Mile Bend). In recent years, with the installation of the 3 new bridges (and other features) closer to Miami to the east, the rules governing discharge of water through the S-12s has been modified to help steer more of the Park’s water into the main thalweg commonly called Northeast Shark River Slough.
Thalweg is just a fancy way of saying “the main channel of a stream.” Usually a riparian term, I like using it for sloughs and strands, too. For example, Roberts Lakes Strand is over a mile wide, but its primary thalweg is a quarter mile, even less.
The beef with the S-12s is that, while they were a victory to the National Park Service at the time they were built in the 1960s (i.e. helping the Park get a foot in the door of securing an upstream water right), they were located on a higher part of the Everglades. Also factoring in was the Park’s 1988 expansion to include Northeast Shark River Slough. That’s where and why the new bridges to the east are so important. They are not only located in the lower spot, they are longer — thus allowing the water to spread out. At least that’s the theory.
If I had a vote or could throw my hat into the mix (is that a saying?), I’d like to go on the record as speculating that larger bridges would be good for Big Cypress National Preserve, too. I know it’s a little more expensive, but the water, trees, alligators and wading birds would love it!