Dec 1, 2016

Meteorologic vs. terrestrial seasons

Meteorologically yes, it's been a "dry" dry season.

But it terms of the terrestrial water cycle, it's still wet out there.


D
ouble-layered swamp cycle revealed

Unlike the meteorologic water cycle that is defined by its two halves (i.e. a summer wet and winter dry season), the swamp's terrestrial water cycle has four parts (as shown above and described below.)
  • Soaking in season. The early part of May is usually the crunchiest time of the year to walk through the swamp: water is absent except in the deepest pools. By month’s end the wet season will have started, followed by June – the rainiest month of the year; yet only rarely do waters peak this early. Late May through June is usually a “soaking in” season for the preserve.
  • Sheetflow season. The onset of summer, lasting into early fall, coincides with an extensive but ephemeral sheet of shallow flowing water in the swamp. Its flowing aspect is achieved when waters rise to the base of the hydric pinelands (i.e., a depth of 20 inches in the pond apple swamps) and higher. The depth, spatial extent and flow rate of sheetflow typically peak between late August and early October.
  • Hydrologic Interregnum. Starting with the demise of sheetflow in mid fall and lasting through winter is the hydrologic interregnum. This is an approximate five month period in which “wet season” water is still present on the ground, but atmospherically the “dry season” has set in, thus initiating the slow demise of the swamp’s expansive sheet of surface water. The duration of surface water in any one spot is largely habitat dependant, but may also be sustained by winter rains, particularly during El NiƱo years. Pinelands go dry first, followed by marl prairies which eventually leads to a retreat of waters into the tall cypress and pond apple swamp.
  • Spring drought. The swamp ebbs to its low water mark in April and May due to the cumulative effect of months with little rain and increasing rates of evapotranspiration (rising temperatures, expanding hours of daylight, and plant transpiration). During this period, surface water is practically absent from the swamp other than smallish (typically less than an acre) and isolated pools called dry season refugia.

Comparison of swamp water depth, this year and last

W
e are currrently in the hydrologic interregnum, a time lag of sorts, that defines the lag in time when the winter dry season has begun but ample, if also dwindling, summer wet season water is still on the ground (i.e. in the lower spots.)

Don't expect it to get really dry until the spring drydown starts.

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