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).

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.