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.
LOCATION.--Lat 27°51'34", long 82°23'04" referenced to North American Datum of 1927,
Hillsborough County, FL, Hydrologic Unit 03100204, on U.S. Highway 41 bridge,
0.6 mi north of Gibsonton, and 1.1 mi upstream from mouth.
DRAINAGE AREA.--418 mi2.
PERIOD OF RECORD.--January 1987 to September 1989 (tidal stage data);
October 1998 to September 2003 (maximum and minumum only); October 2003 to September 2010
(tidal high-high and low-low only); October 2010 to current year
(maximum and minimum only).
GAGE.--Water-stage recorder. Datum of gage is at National Geodetic Vertical
Datum of 1929 and 0.89 ft below North American Vertical Datum of 1988.
Prior to October 1, 2004, datum of gage is 10.0 ft below NGVD 1929.