A retrospective of the dike that controls the Lake
By William J. Sobczak and Robert V. Sobczak
Introductory excerpt from a draft paper
Did you know that if you straightened it out, the 143-mile long earthen mound that surrounds Lake Okeechobee would stretch from Florida's East to West Coast (i.e. Palm Beach to Sanibel, Florida). Yet few people make the trek into central Florida to visit the dike.
Lake Okeechobee – not Herbert Hoover Dike – is the more common destination point.
Okeechobee originates from the Seminole Indian terms “oki” and “chubi,” which literally translates into “Big Water,” and indeed it is. Situated in the center of the peninsula, it is the largest freshwater body in the Southeastern United States (2nd largest in the U.S., excluding Hawaii and Alaska), spanning 730 square miles and 5 counties (Glades, Marketing, Hendry, Palm Beach, and Okeechobee counties), and contains water as far as the eye can see [Figure 1]. Standing at its eastern shore – at Port Mayaka or the Pahokee Marina – the expansive lake looks more reminiscent of the Gulf of Mexico or some other saltwater sea, not a land-enclosed lake.
The Lake is so large that it even influences regional precipitation patterns by stifling daytime heating and the convectional rise of air that brings ample afternoon showers to much of peninsula Florida. As a result, the Lake receives less rainfall than the rest of south Florida (Figure 2).
And who could deny, from a bird’s eye view, Lake Okeechobee’s place as perhaps the Sunshine States most iconic geographic feature other than its long coastline. Simplified maps of the state invariable include three things: the panhandle to the west, the peninsula jutting to the south and Lake Okeechobee, in the middle of it all, also known as the “Big O,” “liquid heart of Florida,” “Lake O,” or simply “The Lake” which is always capitalized in homage to the oversized area and role it consumes in Florida life (Figure 1).
Yet, despite the oversized aura it invokes both inside and outside the state – somewhat surprisingly the most common experience for those closest to it, driving by it from either coast, is to miss it completely.
How is that even possible?
The reason is the 12 meter (35 ft) high grassy hill or mound that blocks the view. Not a natural feature at all, the well-trimmed rise is a 143-mile long levee that forms the perimeter of the modern-day lake.
Interestingly – and a hint to the primary thesis of this paper – it is the shape of the levee, not the Lake itself, that forms the recognizable 730 square mile area that we know as the modern-day lake today. With the exception of an opening at Fisheating Creek that allows the stream to free flow into the Lake’s at its western shore, the rest of the Lake (almost its entirely) is walled off from the lands that surrounded it. Surface-water inflows and outflows to the lake no longer occur naturally, but rather are regulated through a series of human-operated structures and gated culverts.
Thus the question can be raised:
Is it still appropriate to call Lake Okeechobee a lake at all? Would the name Okeechobee Reservoir be a better fit?
As for a clear view of the lake, one would think climbing to the top of the levee, the highest spot for miles around, would reveal its large expanse. But not even that is a guarantee. The majority of the view from atop the 143-mile long levee is obscured by some combination of wetlands, canals, islands or other vegetation. It’s peaceful, often sunny and quite bucolic view, just not the open expanse a first-time viewer would expect.
Despite difficulty (and adventure) in trying to catch a view of it – and the sense of reward when you finally do – the Lake lies in the center of a simmering debate on how it’s water stage should be managed.
Why Lake stage matters at all isn’t intuitively obvious.
Like any reservoir, the Lake fluctuates up and down both naturally and through anthropogenic controls – and most importantly by an official and legally-binding regulation schedule developed and operated by the U.S. Army Corps of Engineers (USACE).
Yet to the naked eye, the levee towers high above the Lake’s water surface – well above the level that any flood could conceivably overtop – and also appears as equally strong at its base.
The more common observation by the casual observer is that the levee is overdesigned. The threat of the Lake breaching such a mammoth feature seems fanciful at best.
The same casual observer may find it surprising to learn that it was problems with the structural integrity of the levee, and the threat of it breaching, that caused the government agency who built and maintains the levee – the U.S. Army Corps of Engineers (USACE) to adopt an interim (i.e. emergency) regulation schedule in 2008 until such time that the levee could be fixed. The interim regulation schedule protects the levee by keeping the Lake at a lower level.
Over a decade later, with most of the primary fixes either in place or nearing completion, the newly fortified levee is in capable of handling higher water. But how high? And what were the pros and cons of the interim operation schedule and, going back into time, all the operational schedules that came before?
The USACE is currently leading a new effort called the Lake Okeechobee System Operation Manual (or LOSOM for short) for the purpose of adoptive a new regulation schedule reflective of the fixes to the levee and other regional water management features that have come on line since 2008. As it does with all its projects, the USACE is actively engaging and seeking collaborative input from individuals and organizations with diverse perspectives.
Many stakeholders are interested in the Lake and how it is managed for the integral role it plays from environmental and human-use perspectives both internal and external to the levee.
Yet going back to the casual observer standing on top the levee at the Moore-Haven S-77 Lock and Dam on a sunny day, the overriding reaction would be a bit of a headscratcher:
How could such a large levee be not strong enough?
And other that breaching the levee, why does water level matter at all?
View hydrographs for the Water Conservation Areas (WCA)
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!
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.
But my only hope for ever becoming one is to graph as much information as I can in a format that others can understand and fill me in one what else needs to be added, and how to clear up the confusing points. Things I’ve learned: Sometimes you have to throw in everything, even the kitchen sink. I’ve also found by doing so I get solid feedback on how to make the right tweaks. My first water management breakthrough I’ll never forget was with Cal Neidrauer. He could have easily said: “Bob, you have no idea what you’re doing.” Instead, his only complaint was that I was filling up everyone’s email boxes and suggested I figure out a way to post it on the web. I’m not saying I’ve got it perfect (yet), but it’s always been nice to hear back from Cal and others on next steps and where additions (and subtractions) could improve the over all display.
This graph is a little farther away than the previous post. And it needs a little more labeling, too. What I like about it is that at at a glance you can see the Lake’s level relative to key ecological thresholds, quickly trace it back in time, and also compare it to discharges to the Caloosahatchee and the St Lucie. I also like the map, although it needs better labels. Too often images of the Lake crop out the coasts. But really the coasts are the most important thing to include considering that’s where the consequences are most felt. Sanibel and the Indian River Lagoon deserve a place right beside the lake if you really want to include the Lake’s full regional stakeholders and effects.
Animated hydrograph showing current Lake O stage compared to previous decades
Take for instance the rise and fall of Lake Okeechobee over the decades. If you look at it chronologically year after year, it’s easy to see nothing but a squiggly (or see-sawing ling). But if we look at the data by 10-year increments, tell-tale decadal signals begin to appear. Take for example the nineties and the aughts. The Lake shifted from a state of chronic flood (1990s) to prolonged drought (2000s) as driven by some combination of meteorological and management trends. The chart above shows how current Lake stage measures up to decades past. The table below shows that percent of time that water stage stayed within any one-foot interval (from 8 ft to 18 ft NGVD 1929) from 1950 to 2010. The darker the green, the higher the amount of time water spent within that range.
What’s the ideal stage for the Lake? Probably between 12.5 and 15.5 ft the last I heard. The reason? It keeps the water-quality challenged pelagic center of the Lake from comingling with the oligotrophic littoral marsh while also providing room for flood control should a big storm strike. It will be interesting to see how the new regulation schedule factors into how the Lake is managed in the coming years.
The Chesapeake Bay watershed comprises 64,000 square miles, encompasses six states including Maryland, Pennsylvania, Virginia, Delaware, New York, West Virginia and all of the District of Columbia. The land-to-water ratio of 14:1 is the largest of any coastal water body in the world. But how big is all that in Lake Okeechobee units? Excellent question!
Answer: The Chesapeake Bay Watershed is 88 times the size of Florida’s Lake Okeechobee and the bay itself is six times the size of Lake Okeechobee. I know what you’re thinking: That’s an unfair comparison, i.e. what happens when you throw in Lake Okeechobee’s upstream watershed (including the Kissimmee River Valley, Fisheating Creek, Lake Istokpoga and a few more)? Even then the Chesapeake is a lot bigger — 13 times bigger than Lake O and all its upstream watersheds.
I‘m not saying the Lake isn’t big, all I’m saying is it makes a good measuring cup.