May 9, 2011

How historic is this drought?

How deep is this drought?

It depends on how far back you look.

How dry is it?
"Below staff gage" dry
The hydrograph below shows the annual water stage statistics at one of our longest running hydrologic monitoring stations, located along the Tamiami Trail at Bridge 105. The blue line is the current year and the dotted white line is the 20-year median value. The background color coding puts the current stage in additional context of (1) the twenty-year range in seasonal water levels (i.e., percentiles) and (2) major habitat types in the swamp (i.e., pond apple, tall cypress, marl prairie, and pines.)

Or in other words,

Limited to the last twenty years, the answer is “about as dry as it gets.”

How dry it is depends on how far back you go.

Double that back to forty and suddenly it isn’t as dry.

Or should I say rather, not such a rare occurrence.

Spring droughts of 1971, 1975, 1976, 1982, and 1989-1991, of which 1971 and 1989 are shown on the graph. Not only were they deeper during the spring, those years were drier for a longer duration through the winter and even as early back as the fall.

Tamiami Trail's Bridge 105 in May 2009

But that’s splitting hydrologic hairs:

Deep drought is as dry as the wet season is reliable.

Over the long-term, waters start to rebound by Mid May.

1 comment:

Dave King said...

So it's both optimistic an d pessimistic then? Much like the rest of life.