Hydrologic sink

Ever get the feeling that you’re spread a mile wide but an inch deep?

That’s hydrology in the Everglades!

Or rather, that’s life as a hydrologist in the Everglades.

We call it sheet flow.



Sheet flow season is summer and fall. By winter we still have thin sheets of water, but they are no longer flowing (just evaporating). And by spring, and especially this one, the sheets are gone too.

Somehow that doesn’t mean less work for me.



When I first arrived to Florida, a colleague made a point of regularly stopping me in the hallway with variations on the same question –

“So what are you still doing here, Sobczak? Haven’t you noticed it’s the dry season,” he’d say in mock astonishment, usually ending with a terse and definitive – “All the water’s gone! Go home!”



Another hydrologist may have taken offense (as if there wasn’t enough water to keep me busy for the full year), but being somewhat raised in the comic tradition of beating a dead horse myself, it not only took on a certain amount of charm after his 6th or 7th re-asking (although on occasion I’ll admit it was annoying), I adopted it on a polemic level as a false paradigm that I needed to learn how to refute.

My initial responses were admittedly lame, and uninformed.

“It’s a good time to get out in the field,” I’d say in half-hearted defense.

“And see what – no water?” He’d respond.

Not being easily defeated, I’d have something along the lines of “we still get cold fronts,” on queue for the next encounter, “and they can be big rain days.”

“I don’t know what window you’re looking out,” he’s say dismissively. “All I see is sunshine!”

That sent me back to the drawing board once again where I came up with my best game plan to date – the counterintuitive twist that “yes, it’s the dry season,” and “yes, it barely rains,” but “those zeros are numbers too, and counting consecutive days of no rain is just as important as waiting around for the big rain days.”

“Last time I checked,” he’d counter back, “zero plus any number equals that number.”

It growing later and later into the dry season by the day, and being quite frankly exhausted by the whole line of conversation, I had no other recourse but to throw the kitchen sink at him upon our next chance encounter:

“Rain is just one part of the hydrologic cycle.” I said. “In south Florida, evapotranspiration is just as big or bigger than rain!”

For the first time he didn’t have a quick response at hand.

We shared a moment of silence in the thickening heat of the afternoon hallway.

That’s when we heard a crackle of thunder in the distance.

“You hear that?” He responded. “That’s your sign its time to get back to work. It’s the wet season!”


Somehow I knew I couldn’t win.

Extreme wet and dry

You know it’s dry at Sweetwater when you can walk under the road (through the culverts).



You know it’s wet when you drive through water flowing over top Loop Road.



How do you know we’ve had a “very wet” summer wet season followed by a “very dry” winter dry season?

That’s when you can do both in the same year.

Waterless river

What’s the tell tale sign of the typical dry season?

That would be the cypress going dry.



To see the tell tale sign of a “really dry” dry season, you have to move beyond the cypress and find yourself a deep watering hole.

Even those have gone dry this year.



Big Cypress Nat’l Preserve’s Turner River would be one such example. Its headwater source and channel have all but dried down to its channel bottom. The only flows you’ll find this spring at the bridge is the Tamiami Trail’s traffic over top.

(That’s the road at the end of the short video clip).

Eternal umbrella season

Am I the type of hydrologist that loans you an umbrella during the dry season, only to take it away when the summer rains start back up?

No – I wouldn’t give you an umbrella to begin with.

That’s your responsibility.



What I can do is give you the rain numbers!

But sadly, I can only give you those numbers after the drops have fallen.

That doesn’t do you much good in the wee hours of each morning when you are trying to figure out what to wear, or whether it will rain.

(In Belgium, there is a famous saying that the hardest decision that anyone makes each morning is what to wear … as the weather is often in flux.)

In Florida we sort of have the opposite sentiment –why not just wear shorts all year long?



But back to the umbrella:

My suggestion is to have one with your at all times.

That way, you have one in case it rains… and also in case it doesn’t.

That’s when it becomes a parasol.


Click HERE to view rainfall charts for south Florida.

Double headed summer

When does summer begin in Florida?

If we had to pick a number out of the sky it would be 88º F … or is it 70º F?



For state-wide comparative purposes, Morton D. Winsberg, author of Florida weather (one of my favorite books) defines the beginning of Florida summer as the former – 88º F.

Neither nights nor shade bring relief to the hot grip of summer in Florida.

The rains do bring relief however, at least locally, after they fall … often in deluges.



That brings us to our second number.

The wet season – often used synonymously with the summer in peninsula Florida – is associated with the latter number – the 70º F mark.

The regular routine of convectional and sea breeze fed afternoon showers tend to erupt when night time lows consistently break that magical mark.



If I had to pick a number, I would say both.

Florida’s summer wet season typically runs from late May through early October.

11 ft milestone

Chalk up – or rather “down” – another milestone to this year’s dry season.

Lake Okeechobee has dropped to the 11 ft (above sea level) mark.



What’s the significance of that number?

It’s the level the Lake’s interior marsh goes dry.

Scattered prairie potholes are still holding water (which are a few inches from also going dry), but the big picture is that the Lake’s vast wetland area is dry.



How does this year’s spring recession compare to recent droughts?

In defiance to statistical neatness, Lake O has already recorded two "droughts of the century" in the first decade of the new millennium.

The first was 2001. The Lake dropped below 11 ft in January for 7 consecutive months.

The second started in 2007. The Lake dropped below 11 ft in March of that year, eventually bottoming out at its all-time record low of 8.8 ft in June. In total it stayed below 11 ft for 17 consecutive months.



That brings us to our current situation.

It’s not in drought of the century territory by those standards, but it’s worth noting that current Lake stage is only a half foot above early May of last year, (which several weeks later dropped the lake back near the 9 ft mark).

But that’s when the rains kicked in. The Lake rose steadily through early August 2008, breaking out of its record 511 day streak below 11 ft one week prior to Fay jumping it an additional 4 ft, up to 15.

As high as that jump was, it only brought Lake stage up to the September median (as measured from 1991 to 2008).


Which raises the questions:

When will the wet season begin, and how much rain will it bring?

There’s a Lake in the center of south Florida that could use some water.

Peak tornado season?

Technically tornadoes don’t have their own season.

That’s because tornadoes spawn from severe thunderstorms … which is a weather phenomena that occurs all year round across the North American continent.



But May is peak tornado month for the nation.

That’s a result of increased daytime heating and humidity which, combined with the clash of lingering cold air from the north, puts Tornado Alley on high alert come mid to late afternoon.


Compare that to Florida’s hurricane season.

It runs from June 1st through November 30th, peaks in September and October (accounting for almost 70 percent of hurricane strength Florida landfalls), before precipitously fizzling out in November and December.



That doesn’t tell the full story.

Rains from lesser strength tropical depressions can be just as prodigious as hurricane strength storms.

And yes, hurricanes famously spawn tornadoes too.

But it’s the early spring period, from February to April, when the Florida twisters peak. A twist on those tornadoes is that they are just as likely to occur after midnight as they are in the afternoon.

Not exactly the stuff of sweet dreams.


The good news is you are not likely to see a hurricane or tornado on peninsular Florida in May.

Shades of dry season

I’m a metaphorical thinker, and thus at times find myself succumbing to the generic cliché, the most obvious of which here in south Florida, hydrologically speaking, are wet season and dry season comparisons. They are mind numbingly predictable – one’s wet, the other dry; It’s the equivalent of comparing vistas of winter to summer up north.



That’s what has me thinking about the more subtle dry season (February) to dry season (April) comparisons, and the (this) May to (last) May comparisons.



It surprises me what I see in those photos side to side that I didn’t quite see at the time I snapped each one.



Photo descriptions: (1) Pinelands along Tamiami Trail days after a prescribed burn in February and 3 months later in April. (2) Tamiami Canal 4 months into dry season (February) and 6 months into the dry season (April). (3) Views of same cypress dome days after a February prescribed burn and 3 months later in April. (4) Turner River this May (3 dry photos) in comparison to May of last year (when it was still wet).

Watershed wheels

I was kicking tires up at a Ford dealership north of Naples when a sales attendant approached.

Knowing that I wasn’t really serious about buying, and not wanting to waste his time (or mine), I jumped him with a question before he could do the same with a sales pitch.



“So what was your first car?” I asked.

He was taken back at first by the inquiry but, after a brief pause, was happy to have a nostalgic moment at hand, to which he answered.

“Was that a Ford make?” I asked dumbfounded, thinking perhaps it to be a discontinued model like the Ford Etsel.

I was still trying to process what he said (was it Jensen or Aston), when he blurted out in clarification – “It’s a British model.”



“My first car,” I proudly told him “was a 1974 Ford Elite: black, two doors (each very heavy), 8 cylinders with lots of room under the hood to maneuver. It was a gift from my uncle to my brother and me.”

Then I told him how upon leaving for college my brother’s departing words to me weren’t “hang in there kid” or “I’m only a phone call away,” but rather – “Take good care of the Elite … it’s been a good car.” Not only did he mean it, he’d never been more right: that car was indestructible.

“Sounds like my old Toyota truck,” he said. “That’s the one I had the longest.”



Somewhat perplexed, I intentionally skipped over indulging in any ruminations about my 1991 white Ford Ranger – the one I took out west, drove down into Death Valley, and in the process racked up over 180,000 miles before selling it in near mint condition for a more family friendly sedan –-


Instead opted to bring the conversation in full circle back to Florida and Ford:

“I was just on a tour at the Edison and Ford Winter Estates down the road in downtown Ft Myers.” I said.

He shook his head with a sheepish look. “You know, I’ve never been there.”

Somehow I wasn’t surprised.

Gum Slough

Gum Slough is yet again another one of a kind in Big Cypress Nat’l Preserve.

It’s unusually narrow. You could literally throw a rock across it in most places. (That’s assuming you could find a rock!) Most sloughs are endless as far as the eye can see.

Even more perplexingly, it runs in a due east-west direction. Most flow systems in the preserve – whether they be forested strands or marshy sloughs – have a north-south component to them.

But most shockingly (although not altogether surprising this year), Gum Slough has gone almost completely dry.

Or, at least, as dry as we’ve seen it!



Above is a short video clip of a cypress enclosed marsh in Gum Slough where we monitor its water levels, filmed just last week.

Fourth horseman?

Florida has four meteorological horsemen.

They stampede into town from every corner of the sky. The thunderous approach of their hooves and sun-eclipsing clouds they kick up are cautiously greeted by Floridians with an equal dose alarm and routine:

It’s time to take cover … a drenching of apocalyptic proportions may be on the way.



Who are the horsemen?

Three of our four horseman ride into town in the summer and fall.

They are the enhanced sea breeze (Florida’s bread and butter storms), the giant Cape Verde hurricanes that spawn off the coast of Africa, and the often smaller in strength but gorged with moisture tropical disturbances that arc up from the gulf and Caribbean.


The fourth – the continental front – rides to town, or more correctly stated, usually rides into town, for unpredicable downpours here and there during our 7 month winter and spring dry season.



Not this year, or not enough this year.

Apparently someone forgot to open the “great stable in the sky” and let that horse run free.

Off the beaten Trail

Sometimes you don’t have to go deep into nature to get into deep nature. Tamiami Trail is the perfect example. It’s the main road between Miami and Naples.

I crossed the canal on its north side using an old wooden bridge.

That led me into a wet prairie which, because it’s the dry season – and an especially dry one at that, is better classified as a dry prairie in spring … at least until the summer rains start back up.



This particular dwarf cypress caught my eye because it was short and stout, but probably as old as the larger cypress in the adjacent dome.



The cypress dome was thoroughly greened out but like the prairie dry also as a bone. And this was a deep dome. As flat as the Big Cypress Swamp is, it was a downhill journey to the center of this dome. (The plus side of no water of course was the equal absence of mosquitoes.)



The cypress knees were especially impressive, and rekindled in me a question that has periodically tugged at my curiosity, but one I’ve never been able to answer:

“Why is it that knees are absent from some domes, sparse and smallish in others, and – as in the case of this dome – omnipresent and quite tallish (hip high)?”

I thought about that for a moment, in the silence of the dry dome, periodically interrupted by the thrush of Tamiami traffic on the nearby road … which with Alligator Alley being closed due to a wildfire (named Deep Fire) has been steadier than normal.

Then I left.



I turned once to the east (toward Miami) and once to the west (toward Naples) before crossing back over the Tamiami.

It was good to get a off the beaten Trail, even if for only a few minutes and a couple hundred feet to the north.

Any longer or further and I could have gotten lost!

Seven year slough

Mark your calendars!

Because it only happens once about every 7 years …


And I’m not talking about locusts, or in this case the Everglades equivalent – the lubbers (although come to mention it, they are cyclical too.)

No, I’m talking about Shark River Slough going dry.



This marks Shark River Sloughs lowest April in over 15 years – going back to 1991 to be exact -- as measured at Everglades National Park's P33 monitoring station.

It’s the preceding year, however, (1990) that stands out as the contemporary drought of record, going all the way back to the mid 1960s. That’s the year that Shark River Slough went dry in February.

Shark River Slough’s current level is about a foot lower than the 15-year late April average, and a foot lower than late April of last year.



Compare that the spring flood of record – 1995 – when Shark River Slough was brimming in late April almost 2 feet higher that its current level.

That’s a bit of a shocker because as late as this October Shark River Slough levels were climbing high up the wetland ladder. The difference maker of course has been a dry winter, and now a dry spring.



That has me wondering what such a record dry down means for the lubbers?

Could this be their year too?

You never quite know in the Everglades.

Spring dry out

We commonly split our year in two parts in south Florida:

A summer wet season and a winter dry one, the latter of which has been drier than normal.

(The result was an earlier than normal “dry down.” Our lowest-lying marshes, sloughs, and strands went dry by late February, leaving only isolated pockets of water in our dry-season refugia pools.)



But that bi-modal categorization misses the pivotal role that spring plays in our seasonal drought.


We’re now seeing those effects in full bloom:

Waxing daylight hours, hotter temperatures, a surge in plant transpiration, and often gusty desiccating winds.

Isolated showers quickly soak in, and within days its back to being as dry as it was before. (Don’t get me wrong – we’ll take any rain we can get!)




The winter “dry down” is all but passé; the spring “dry out” is the new concern.

That’s because in south Florida spring is not wildflower season, it’s wildfire season:

All it takes is a lighting strike from one of those isolated showers.