[Scorecard] dry/late season flow indicator

[Bob Zlomke]

Hi everybody,
 
Following up on Rainer's idea, I looked at the monthly mean flow data
for the Napa River at Oak Knoll, in search of the elusive Long-Term
Trend.  The graph below shows mean monthly discharge as a pct of annual
discharge, for the periods BEFORE and AFTER 1980 (in blue and red,
respectively).  There are interesting differences but I see nothing to
suggest a definite shift in the annual hydrograph.  You'll note, for
example, that the April runoff is reduced but that May, June etc. are
increased, changes which might conceivably be important but are probably
more related to random variation in rainfall timing.  These differences
are much smaller than the shift in annual peak from January to February,
which I do attribute to random rainfall variation.  The curve for
2004-07 shows more of the same.  The new spreadsheet is attached.
 
Does anybody have any more ideas?  I have about concluded that there is
no basis for scoring flow persistence (whether we call it dry season
flow, late flow, or whatever) in Napa this time around.  Maybe next time
we'll have the dry reach data Sonoma has.  I will wait for guidance from
Deanne and Caitlin before writing anything further on this Indicator.  
 
Bob
   
 
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