USGS Water-Year Summary for Site 05474500

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	Available Parameters
	00010 Temperature, water(Mean,Ins.)
	00060 Discharge(Mean)
	00095 Specific cond at 25C(Mean)
	00300 Dissolved oxygen(Mean)
	00400 pH(Med.)
	32318 Chlorophylls,in situ(Mean)
	63680 Turbidity, Form Neph(Mean)
	99133 NO3+NO2,water,insitu(Mean)

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Water year 2023: 2022-10-01 to 2023-09-30

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USGS Water-Year Summary 2023

05474500 Mississippi River at Keokuk, IA

LOCATION - Lat 40°23'37", long 91°22'27" referenced to North American Datum of 1927, in SE 1/4 SW 1/4 sec.30, T.65 N., R.4 W., Lee County, IA, Hydrologic Unit 07080104, near right bank in tailwater of dam and power plant of AmerenUE in Keokuk, 0.2 mi upstream from bridge on U.S. Highway 136, 2.7 mi upstream from Des Moines River, and 364.2 mi upstream from Ohio River.

DRAINAGE AREA - 119,000 mi².

SURFACE-WATER RECORDS

PERIOD OF RECORD - Discharge records from January 1878 to current year.

GAGE - Datum of gage is 477.41 ft above National Geodetic Vertical Datum of 1929 (levels by U.S. Army Corps of Engineers). January 1, 1878, to May 1913, non-recording gage at Galland (formerly Nashville), 8 mi upstream, with datum of gage set to low-water mark of 1864, or 496.94 ft above Mean Sea Level, general adjustment of 1912.

COOPERATION - Records provided by AmerenUE (formerly Union Electric Company).

REMARKS - Accuracy of records is discussed in the annual Station Analysis archived at the USGS IA Water Science Center. Discharge computed from records of operation of turbines in power plant and spillway gates at dam. Minor flow regulation caused by power plant since 1913 and navigation dams. Records for May 1913 to September 1937 adjusted for change in contents in Keokuk Reservoir, those after September 1937 unadjusted.

EXTREMES OUTSIDE PERIOD OF RECORD - Flood of June 6, 1851, reached a stage of 21.0 ft, at current site and datum, estimated as 13.5 ft at Galland, discharge 360,000 ft³/s.

WATER-QUALITY RECORDS

PERIOD OF RECORD - Water years 1975-1987, 2008. 2021- current year

PERIOD OF DAILY RECORD -

SPECIFIC CONDUCTANCE: December 1977 to September 1981. May 2021 through current year.
WATER TEMPERATURE: December 1977 to September 1981. May 2021 through current year.

PH: May 2021 through current year.

Dissolved Oxygen: May 2021 through current year.

Turbidity: May 2021 through current year.

Chlorophyll: May 2021 through current year.