Dec 6, 2011

Definitions: Hydrologic Interregnum

The change in meteorologic seasons is quick – like a flip of the switch.

Water on the ground – on the other hand – takes months to leave.

Who doesn't love a Venn Diagram?

I like to think of the winter drydown as the hydrologic interregnum.

Interregnum comes from the political arena: Webster’s Dictionary defines it as the “transition period between a new president elect winning the vote (on Nov 4) and, months later, being sworn into office on inauguration day, January 20th, to replace the incumbent.


The hydrologic interregnum is the multi-month transition period between the start of the meteorologic dry season (November) – during which there is still water on the ground – and the onset of truly dry conditions taking hold across the landscape, i.e. most of the swamp is dry.

The atmospheric dry season is here
by terrestrially the ground is still wet,
(although a little less so each day.)

When does the hydrologic interregnum end?

Three factors come into play: (1) how high wet season waters peaked, (2) how late in the fall the peak occurred, and (3) how much if any winter rains occur. (Some people also add desiccating north winds as another factor.)


Sometimes it’s January 20th, but usually it’s later.

That’s when the dry season’s true reign begins.

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