Data are tidally
affected--Astronomical tides cause significant cycles of
approximately 24.84 hours at this site. Because a different portion
of the 24.84-hour tidal cycle is averaged in successive daily
(24-hour) computations, a systematic secondary oscillation,
unrelated to basin hydrology and having a period of about two weeks
may be apparent in daily data published from January 2002 to
September 2015.