Thursday, July 15, 2010

Saturated Thickness Variability

I'm often asked:  "What's the water table doing?"  It's a perfectly good question, but a difficult one to answer as succinctly as asked - especially in our area where the variability of conditions - from rainfall to actual measured declines - is so variable.  And averages only seem to confuse the issue, so I try to stay away from them. 

Case in point:  our water level elevation data from Thomas County - the heart of our GMD area.  The graph below shows four of the sixty-seven wells measured every Janauary to describe both the water table elevations and the saturated thickness.  (Click on the graph to enlarge it)  The wells are measured to the nearest 1/100th of a foot.  These 4 are the observation wells with:  the most saturated thickness (ST) in 1965; the least ST in 1965; showing the most decline (1965-2008); and showing the least decline (1965-2008).  I have also included (heavy black line) the annual average of all 67 wells.

From these 4 wells we start to see the variability within 1 County - not only in saturated thickness (from 62 feet to 175 feet) but in decline rates as well (from 5 feet to 38 feet).  And if you think spouting average values is misleading (or at least less than helpful) try answering with ranges of values.  Even less helpful to most.  And I've not even gotten into the variability over time, which finds our decline rates at any location changing from decade to decade - due mostly to longer term precipitation variability.

It wouldn't be so bad if it was just water level data, but it's other data as well.  The variability of our rainfall numbers for example stagger even the most hardened meteorologist.  So is the life of a groundwater manager.  Maybe I take it all too seriously.  Maybe people are asking me the rhetorical, ice-breaker question and really aren't that interested anyway.  And maybe that's why I keep all this stuff on our web page - so you can conclude your own answers. 

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