PROVISIONAL DATA SUBJECT TO REVISION

 
DRAINAGE AREA.--11,560 mi2.
PERIOD OF RECORD.--March 1930 to current year.
GAGE.--Water-stage recorder, crest-stage gage and concrete control. Datum of gage is  37.95 ft above National Geodetic
   Vertical Datum of 1929. Prior to June 7, 1930, nonrecording gage, and June 7, 1930, to Jan. 22, 1965,
   water-stage recorder at site 1 mi upstream on right bank at same datum.
REMARKS.--Diversions since June 1959. U.S. Geological Survey satellite data-collection platform at station. 
EXTREMES FOR PERIOD OF RECORD.--Maximum discharge, 484,000 ft3/s, Mar. 19, 1936,
   gage height, 28.1 ft, site then in use; minimum daily discharge observed at gaging station, 121 ft3/s, Sept.
   9, 1966, does not include diversion of 489 ft3/s for municipal use; minimum daily discharge (adjusted),
   601 ft3/s, Sept. 10, 1966, includes diversion of 449 ft3/s for municipal use;
   minimum discharge, 66 ft3/s,  Sept. 9, 1966.
EXTREMES OUTSIDE PERIOD OF RECORD.--Flood of June 2, 1889, was of approximately the same magnitude
   as that of March 19, 1936.
COOPERATION.--Funding for the operation of this station is provided by the Metropolitan Washington Council of
   Governments, and the U.S. Geological Survey. Access to gage site provided by the Baltimore District,
   U.S. Army Corps of Engineers. Water temperature and specific conductance monitoring are supported
   by the U.S. Army Corps of Engineers.

Revised Records: Prior revisions to drainage area are documented in Water Supply-Paper 726. Prior revisions to maximum discharge are documented in Water-Data Report WDR-MD-DE-75-1.