Jan 28, 2014

Meteorologic midway point

Water levels are dropping, right?

Answer: Not as quick as you may think.

This hydrograph shows a comparison of where water levels in Big Cypress National Preserve are now relative to the previous seven years.  The blue line shows the rise and fall of the water table since 2008.  The dotted black line shows the historic median water level from 1991 to present.  The gray background shows the record high and low range over the 1991 to present period.  The little red circles indicate the water level in late January of past years for easy comparison to this year's current late January condition.

Considering how little rain has fallen this dry season (i.e. we are below the 25 percentile in terms of cumulative rainfall for this point in the dry season), water levels are holding up. The reason for that is that evapotranspiration (ET) is down. We never have a truly cold (i.e. shivery) season in south Florida, but we do have a several week span where the effect of ET on the water table diminishes to near zero. Low rainfall during the months of December and January is usually no big deal. It isn't until the dry season starts warming up in its second half that rainfall becomes critical.

Several weeks of no rain in March or April can quickly cause drought.

Halfway into the dry season Big Cypress Nat'l Preserve has recorded 3.5 inches of rain.  The long-term average for this point in the dry season is closer to 6 inches.

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