LOCATION.--Lat 42°04'09", long 91°47'06"
  referenced to North American Datum of 1927, in SE 1/4 SE 1/4 SW 1/4
  sec.21, T.84 N., R.8 W., Linn County, IA, Hydrologic Unit 07080205,
  on right bank 5 ft downstream from bridge on Blairs Ferry Road in
  Palo, 0.6 mi downstream from Bear Creek, 800 ft upstream from Dry
  Creek, and 100 mi upstream from mouth. (map)
  DRAINAGE AREA.--6,342 mi2.
  SURFACE-WATER RECORDS
  PERIOD OF RECORD.--Discharge records from March 2009 to current
  year.
  GAGE.--Water-stage recorder. Datum of gage is 725.71 ft above
  National Geodetic Vertical Datum of 1929.
  WATER-QUALITY RECORDS
  PERIOD OF RECORD.--Water years 1992, 2001-2002, 2004, 2011-2012.
  Period of record includes water-quality data published in USGS annual
  reports and various project reports.