LOCATION.-- Lat 42°15'39",long 90°25'23" (NAD of 1927),in SE1/4NW1/4sec.18, T.86 N.,R.5E.,Jackson County,Iowa, Hydrologic Unit 07060005, on right bank at Lock and Dam #12, 0.2 mi north of Bellevue, Iowa, 8.0 mi downstream from Galena River, 11.7 mi upstream from Apple River, and at mile 556.7.

DRAINAGE AREA.-- 82,400 mi² (determined by U.S. Army Corps of Engineers).

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: October 1994 to September 1997.

STAGE: Water years 1995-1997. Gage-height record for May 14, 1939 to Sept. 30, 1997, available in files of U.S. Army Corps of Engineers.

SURFACE-WATER QUALITY

SEDIMENT: Water year 1995-97.

MISCELLANEOUS: Sediment concentration and particle size, water years 1995, 1997.

GAGE.-- Water-stage recorder and U.S. Army Corps of Engineers satellite telemeter. Datum of gage is 580.20 ft above NGVD of 1929 (levels by U.S. Army Corps of Engineers) (580.06 ft NAVD 1988).

REMARKS.-- Some regulation by lock and dam 11 upstream from station at Dubuque,Iowa, and by lock and dam 12 at station.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 193,000 ft³/s Apr. 15, 1997, gage height, 20.61 ft; minimum discharge, 16,500 ft³/s Sept. 4, 1996.

SEDIMENT CONCENTRATIONS: Maximum daily, 245 mg/L, April 7, 1997; minimum daily, 3 mg/L, Dec. 26, 1995-Jan. 12, 1996, Feb 2-14, 1997.

SEDIMENT LOADS: Maximum daily, 84,000 tons, April 7, 1997; minimum daily, 221 tons, Dec. 17, 1994.

EXTREMES OUTSIDE PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Flood of Apr. 26, 1965, reached a stage of 23.51 ft, from information by the U.S. Army Corps of Engineers, discharge not determined.