Mighty Susquehanna
And the dam that (tries to) control it

The upstream dam …

turns on and off throughout the day.

Looking upstream through the fog and snow to the Conowingo Dam

But it’s never enough to completely shut the river off. The Susquehanna Flats are wide. About a mile to be exact. This photo is taken about 2 miles downstream of the Conowingo Dam that was completed in 1928, coincidently the same year as the Tamiami Trai. So who would have ever thought: a thousand miles apart, the headwaters to Chesapeake Bay and the Everglades got cut off on the exact same year.

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

Splashy, mushy and crunchy
The three states of the swamp

Swamps are by definition wet …

But not always, and sometimes very much so.

The chart above shows the annual duration (in months) that Big Cypress National Preserve spends in the “splashy” and “crunchy” mode. Each summer and fall, waters rise high enough to make the swamp “splashy.” That means water is up high enough to splash at the base of the higher-ground slash pine tree trunks. On average that happens around 4 months per year (light blue), with one month on average being high enough to flood into the mesic pines islands (dark blue). Then there’s the crunchier half of the year when even the center of the cypress domes go dry (red). That happens on average about 1.5 months per year, and usually between March and May. Our driest (or crunchiest) spring on record was in Water Year 2010 when the swamp completely dried out for over 4 months. And then there are the years it doesn’t dry out at all (i.e. Water Years 2009 and 2016).

On average, the Preserve inhabits its extreme states of “splashy” and “crunchy” for almost 6 months per year, or about half of the time. As for the other half, the best way to describe it is “mushy:” a little crunchy dry ground, some splashy puddles and a lot of mushy (i.e. muddy) soils in between.

In summary, on average the swamp spends as much time in its extreme modes of flood and drought as it does its normal mushy period in between. The next big question in the swamp: How deep and long will this spring’s crunchy season be? In the meanwhile, we still have a few months of mushy season to enjoy.

water table

Feast and famine
Why the summer bounty never lasts

One thing we can count on with the water cycle …

No two years are alike.

Hydrograph of water levels in Big Cypress National Preserve comparing this year (blue line) to last year (red line)

Yes, it’s true: We have the average year (shown as the “normal range” band in the hydrograph above) that we compare current conditions to. But in my memory we’ve yet to see a year that stays completely within the “normal range.” This year for example, water levels in the swamp were tracking low for much of the summer. Then came a wet end of September and above average October rains, plus a drenching November rain. The result? Water levels are above the normal band. But how long will that last? Answer: Probably not as long as last year’s record wet winter. However, even last year’s record TS Eta rain event, the water table still dropped down into a fairly deep drought by the end of the spring.

No matter how big the summer bounty of rain, canals and levees rig the swamp for a dive into spring drought without the timely arrival of dry season rains.


Sheet and spring flow
Similarities and differences

One spreads out …

And the other discharges from one spot.

Sheet flow in Big Cypress National Preserve, Florida

Spring flow at Silver Spring in Ocala, Florida

Other differences? One flows all year round. The other lasts for a few months. One gushes fast. The other moves as slow as snail. One is ground-fed and the other gets its water mostly from the sky. One is deep reaching down into underwater caverns that require Scuba gear to explore. The other is shallow thus allowing you to explore by foot (so long as you’re willing to get your socks wet).

As for similarities? Both are crystal clear in their undisturbed state. And both are tranquil beyond belief. Most of all, both need our help to keep them that way.