LOCATION.--Lat 41°27'28.5", long 93°39'17.1"
  referenced to North American Datum of 1927, in SW 1/4 NW 1/4 SW 1/4
  sec.20, T.77 N., R.24 W., Warren County, IA, Hydrologic Unit
  07100008, on left bank 10 ft downstream from bridge on County Highway
  R57, 1.7 mi southeast of Norwalk, 5.2 mi upstream from Middle Creek,
  6.2 mi downstream from Badger Creek, and 22.8 mi upstream from mouth.
  (map)
  DRAINAGE AREA.--349 mi2.
  SURFACE-WATER RECORDS
  PERIOD OF RECORD.--Discharge records from February 1940 to current
  year.
  REVISED RECORDS.--WSP 1438: Drainage area. WSP 1508: 1946. WDR
  IA-76-1: 1975 (P).
  GAGE.--Water-stage recorder. Datum of gage is 788.45 ft above
  National Geodetic Vertical Datum of 1929 (levels by U.S. Army Corps
  of Engineers). Prior to June 12, 1946, non-recording gage at same
  site and datum; January 7 to October 11, 1960, non-recording gage at
  site 2.1 mi upstream at different datum.