Indices illuminate

Rain or Shine Report for March 3

Big Cypress records 25-yr February rainfall high
Lake still above 10 ft mark, but still at all-time March low

Aerial view of mixed cypress and pineland forest in Big Cypress National Preserve in winter. February rains reflooded the cypress domes and strands of the preserve.

If economics is the dismal science, that makes hydrology the wet science; and both have indices to help us simplify the math.

A few weeks back I commented on Lake Okeechobee stage being comparable to the financial world’s Dow Jones Industrial Average (DJIA).

It’s not a perfect analogy by any stretch. In absolute terms the Dow keeps going up and up – a virtual stairway to the stars, … over the long-haul at least.

(Pay no attention to its recent hover between $1200 and $1300 per share: that’s just an artifact of jittery consumers wadding through a rough patch of slumping home values, the rise of a barrel of oil above $100, and weakening buying power of the dollar. I’m hearing that it will probably regain its upward momentum by year’s end.)

By contrast, the big lake rises and falls, rises and falls, from one year to the next, and over the decades — and is not the steady rise upward like the Dow.

But in terms of simplifying life’s complexities and putting a face to sometime too large to fully understand in all its details, indices – whether financial or hydrologic – definitely have their place under the sun. They may not tell us everything, but they give us what we need to know at a glance, and can help frame it relative to the historical parade that came before.
Without such an index its hard for the normal person to even discern when a drought starts, ends, how severe in magnitude or long in duration it is, or — even more alarmingly — that there is a drought at all. That’s how buffered we are from the environment!
That is another way that hydrology similar to the economy, and the Lake similar to the Dow. Yes, the Dow is down, but the majority of people on the street would be hard pressed to know the difference between a bull and bear market, and how and if it affects them in the moment. That’s what indices are good at: turning static into a simple signal that puts us all on a common page, and within the same conversation.
One cannot dispute the usefulness of indices – but by no stretch do they tell the full story, and can only semi-predict the future at best, given counfounding or amplifying influences of other forces and large doses of uncertainty.
These days, we have become transfixed with trying to find a global teleconnection for any bump in weather patterns – such as blaming global warming, El Nino or La Nina, or some other global scale cycle. But truth be told no matter what happens with the climate, there will always be good old fashioned weather and its unpredicability.
That is pointed out in article in this Sunday’s New York Times. It explains how La Nina episodes — like the one we are experiencing now — have been linked to brief pauses (and declines) in the decades-long atmospheric warming trend. Some pundits have cherry-picked this year’s winter downturn as evidence in refutation of global warming. But just like you can’t draw a graph from a single dot, its impossible to foreshadow a climactic trend from one season, or one event.

Being a Floridian – or denizen of any part of the globe for that matter – what we wake up and see every day is the local weather. The same La Nina that has cooled the planet this winter has cast the spell of a balmy winter here locally in south Florida. The La Nina and El Nino extremes of the ENSO teeter-totter is famous for painting a semi-predictable tapestry of contradictory weather patterns across the globe.

The Lake level is an imperfect indicator of drought in south Florida. Drought has a way of not descending evenly across rain-abundant (but seasonally tempermental) south Florida – some areas are at multi-year high water marks for this point in the dry season, even though the Lake is at its lowest early March level ever.

But as the backup water supply for the east coast and agricultural users, the hydrologic pivot point between the Kissimmee, Everglades and the estuaries, and just being the biggest water body on the local and regional map – the Lake’s level warrants attention; and connects us all as south Florida watershed enthusiasts.
Its our Dow.
The Lake is still hovering slightly above 10 ft.
View of Lake at Port Myacca in June 2008
Last winter, the big lake dropped below the 10 foot mark for a 5-month duration. After this summer’s below-par 25 inch rainy season (the long-term rainy season average is closer to 35 inches), the Lake rose didn’t rise back above the 10 foot mark until October 2007 – and just barely (it never exceeded 10.6 ft).

What’s sort of incredible is that the Lake has stayed at pretty much the same level – in the low 10s – for 5 months now. And currently the Lake is around a half foot higher than it was in mid September.

Compare that to the year prior – from September 2006 to March 2007 – during which the Lake declined 2.5 ft, from 13.5 to 11 ft msl.

Keep in mind that the Lake is still around a foot lower than early March of last year (2007), and that last year the lake didn’t drop below the 10 ft mark until early April. All indications are that the Lake will drop back below 10 this week; barring more rain or releases from the headwaters from the Kissimmee finding their way down to the Lake.

Speaking of rain, the final front of the month brought more rain to Big Cypress National Preserve. The 0.3 inches was just enough to tie the previously 25-year February high recorded in 1998, but an inch shy of the February rain total that fell during the first El Nino of the Century – in 1983.

Suffice it to say it was a enough to reshuffle the hydrologic deck in Big Cypress National Preserve.

The swamp forest, cypress domes, and cypress strands remain filled with water – with the outer edge of the wetting front still reaching its tendrils into the preserve’s wet prairies. Preserve-wide stage is currently around a half foot higher than the 5-year average for early March.

The February jump in wetland stage was enough to restart surface-water flows under the Trail. The US Geological Survey measured around 800 cubic feet per second under the 35-mile stretch of Tamiami Trail between Carnestown and 40 Mile Bend at the end of February. That flow rate matches what was flowing under the Trail at the tail end of the wet season (in October) and comes after almost 3 months of flowless conditions under the Trail.

Regulatory stage in Water Conservation Area 3 is now tracking along the 5-year average for early March. That return to normalcy occurred after 3A spent much of the summer more than a foot below normal summer stage levels (of past 5 years). Of note, the S12D gate was re-opened last week; it is currently releasing a few ten cubic feet per second into downstream Everglades National Park.
S12D looking east along the Tamiami Trail

Everglades National Park’s Central Shark River slough is at its lowest early March level since 1991. And annual inflows into the Park through the S12s were at a 17-year low in 2007.

Entrance to Everglades National Park’s Shark Valley tram.

In the northern Everglades, Loxahatchee and Water Conservation Area 2 are both at 5-year highs for early March. The S10s are no longer flowing, but around 1000 cfs are still flowing through the S11s into WCA3.

Corkscrew is coming of its lowest wet season since 1970. But with the February rains, stage levels briefly inched back into the swamp forest wetlands. Currently stage at Corkscrew is tracking about an inch or two below early March of last year, and about 10 inches below the 5-year early May average.

Of note in the Kissimmee Basin, north of Lake Kissimmee over 500 cfs are flowing out of Lake Toho, and over 1000 cfs is flowing through Cypress Lake. I am not as familiar with those systems as I am with the Everglades to the south; I’m assuming the flows are from the recent rain, or will they being released to help sustain flows in the downstream river?
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