Tuesday, September 27, 2011

Another Hydrograph to Consider

Most of our observation wells for NW Kansas are functional irrigation wells that are measured in the Winter each year after they shut down - usually in early to mid-September.  As such, these wells are normally recovering to some degree from their irrigation season pumping levels when the annual measurements are made.  About 25 of the 280-some measured wells within GMD 4 are listed as "unused", so this group of wells may need to be looked at a little differently.

The hydrograph shown (click to enlarge) is one of these wells.  It is located in SW Sheridan County and has a water level record spanning December 1964 - December 2010.  This well was one of the original wells that was measured quarterly until 1997 and annually thereafter.  The measuring frequency doesn't affect much as you can see from the hydrograph - with the overall trends being clear, regardless. 

This well is showning a decided decline since 2000, but we see that it has been as low and even lower in both 1980 and 1990.  It appears to be showing a more regional perspective on the local water table - since it is itself not pumped annually.  Statistically the entire decade of the 1990's was several inches above normal precipitation in NW Kansas while we have been a bit droughty since 2000.  The hydrograph certainly bears this out.  It also appears that the regional climate may have been wetter from 1980 - 1985 and drier from 1986 - 1990, but I'll have to check this out to be sure.

This well is 184' deep (BLS) with the December, 2010 water level being measured at 105' BLS.  How long the remaining 79' of saturated thickness may last is anyone's guess, but this particular observation well is interesting in that it has a clear decline trend from 1964 - 1980 (11 feet of decline in 16 years), then looks fairly stable since 1980, but with several, significant, decadal-termed fluctuations.  Oh, the joys of groundwater monitoring. 

If you'd like to see the full data for this observation well, use this link:  KGS Wizard Database .  If you'd like to see any specific observation well covered in this manner, let me know.  Of course you can see every observation well in Kansas on the KGS Wizard site.  More later.

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