The Caloosahatchee: How a small stream became a major spillway
By Robert V. Sobczak and Jack Meeder
Summary: In modern times, the Caloosahatchee serves as the primary high-water spillway for the Lake and the Everglades. The following is a brief history of the river that also features some up-to-date charts. Enjoy!
Early History of River
The dredging of the Caloosahatchee River, and specifically blowing up of Ft. Thompson Falls in the 1880s, is often invoked as the starting point of drainage of Lake Okeechobee and the Everglades.
In the years and decades that followed, the Caloosahatchee would go on to become the primary outlet for controlling Lake stage, a status it retains to this day. In many ways it functions as spillway for the greater Kissimmee-Okeechobee-Everglades (KOE) flow way, and in particular for the Lake.
Not a single act, direct dredging of the river – including digging a straight channel through its tailwater oxbows, blowing up the Ft. Thompson Falls, connecting it to the Lake, and deepening the channel for nautical purposes throughout – and construction of a vast network of tributary canals that drained into it (from the north and south) occurred over a span of decades. The Caloosahatchee River was a rare case where nautical and drainage interests initially fought against each other but ultimately both won.
The original Caloosahatchee was more reminiscent of a stream in terms of its meanders and relatively shallow depth. The river was sinuous to the point of being unnavigable, requiring larger vessels to “warp-around” the curves, requiring running their bow on the shore and using a rope to swing the boat in the right direction (Antoni et al, 2002). Moreover, the stream stopped short of the Lake, about halfway to be exact, where the smaller (and now dried up) Lake Flirt basin served as its headwater source.
The modern-day Caloosahatchee is a deep-water nautical channel, Lake Okeechobee’s primary outlet, and flood-water drain for its adjacent lands to the north and the south.
As a result,
Caloosahatchee is now a channelized spillway, not a natural river
Historic Lake Flirt and Lake Bonnet no longer exist,
Modern-day water levels north of Ft Thompson falls are upwards of 10-15 lower than their pre-drainage condition.
The Caloosahatchee doesn’t just drain Lake O, it’s also the primary getaway canal (C-43) for draining lands to the north and south of the river. This drainage capacity is enhanced by a series of tributary canals along the modern-day river’s entire length.
View Caloosahatchee Hydrographs
The channel did more than just connect the river to Lake O.
Not all the water that discharges through the S-79 is from Lake Okeechobee. Approximately half comes from the Caloosahatchee watershed and those tributary canals.
The water table under the Immokalee Rise dropped below the regional surface water table.
Drainage of the Caloosahatchee caused the headwaters of Okaloacoochee Slough to reverse course. At some point Big Cypress Swamp’s pre-drainage watershed now flow north into the Caloosahatchee River, both groundwater (unseen) and surface water as seen at Okaloacoochee Slough.
Today, the Caloosahatchee River (C-43) is managed by the U.S. Army Corps of Engineers (USACE). It should be noted that by the time the USACE arrived on the scene, the Caloosahatchee was already dramatically altered from its natural condition. Water control on the mainstem of the Caloosahatchee occurs at three lock and dams: the S-77 (Moore Haven), S-78 (Ortona 9 miles upstream of LaBelle) and S-79 (W.P. Franklin at Olga)
Of particular importance, and closely watched is Caloosahatchee discharge at the downstream the S-79, shown below.
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.