Water Depth

water table

Rise and fall of Swamp
And why its the norm (but it won't last)

The swamp falls …

and rises (sometimes from the ashes).

A look at the previous four water years

It’s called the water cycle, and more specifically — the wet and dry seasons. Unlike Up North on the continent where they have four traditional seasons, the swamp has two, meteorologically speaking at least. So, in the way of a quick review: Last wet season got off to a slow start. The water table didn’t bottom out until mid June in some places, usually a reliably rainy (if also soaking in and rising up) month. Compare that to this year’s rainy season which — thanks the Big Rain Day (BRD) this weekend — is off to a fast start. Or rather normal. The blue line (current condition) is tracking very closely with the long-term norm (white line). In summary: The swamp rises and falls. Currently it’s rising. And looking back, has there every been a 9 month span that the water table tracked so closely to the long-term normal — I wonder? If so, it isn’t a trend I expect to last.

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Swamp tidbit: A vertical elevation of just 2.5 feet separates the swamp’s low-lying wetlands from its natural high ground.

water table

Two months of drop
And four more to go

Water levels in the swamp …

Have been steadily dropping for two months.

Hydrograph of water depth in Big Cypress Nat’l Preserve
Historic calendar of water depth in Big Cypress Nat’l Preserve

The reason? That’s what it always does. It is a bit surprising that the pop-up storms of December didn’t do more to steady or reverse the recession. And that’s not to say we don’t have a big water-cycle reversing storm in the dry season cards yet. What we can say is that water levels are a foot lower than this time last year and an inch or two below the long-term average for early January. The long-term forecast is this: We have four more months of dry season until the summer rains start up.

In the meanwhile, if you get out into a dome or a strand, you’ll still find plenty of water, and a good amount of moisture in the marl prairies, too. It isn’t until March, April and May that the swamp dives down into deep drought.

water table

Optimal Lake Stage?
The answer has changed over time

Prior to drainage (pre-1882),

The optimal Lake stage was 22 feet above sea level.

Lake O cross section, then and now

That’s the level it naturally drained south into the Everglades downstream. In modern times, the question gets bogged down in a complexity of water management schema, stakeholder clout and the constraint of the Lake’s perimeter dike. No longer allowed to spread out, high waters are drained through a release valve to protect wetlands on the inside of the dike instead of replenishing the wetlands it used to feed to the south. The primary release valve is called the Caloosahatchee River, although technically to get to the main river stem (which is actually a widened canal called the C-43), water has to first drain through Three Mile Canal. Prior to drainage the natural river ended at Ft. Thompson Falls just upstream from present-day LaBelle and 20 miles from the Lake. Yes, it’s complicated, and muddled (and muddy). It’s called modern times.

The thing about the dike, and this has always been the case:

It was built to control water on outside, not inside, its bounds.

WCA3A Update
Deepest pool is shallower than normal

Hydrograph of WCA3A in the Everglades
Hydrograph showing current water depth (blue) relative to the elevation of major habitats of the ridge and slough ecosystem, the statistical record from 1993 to present and the new regulation schedule (COP)
Calendar chart of water depth in WCA3A of the Everglades
Calendar chart of water depths in WCA3A using the same color scheme as the hydrograph above

At first glance, the water table looks simple.

You can touch it with your finger and sure enough it’s wet.

The difficulty lies in understanding where it’s at relative to the suite of hydro-ecological and statistical metrics we measure it by. Case in point is Water Conservation Area 3A in the Everglades. Statistically, it’s a foot below where it normally is for late August and three feet below its high-water crest following Eta. Ecologically, water depth in the sloughs are about 1.75 feet deep but the tree islands are still dry.

That’s relatively rare for WCA3A this late in the summer.

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