USGS Water-Year Summary for Site 09421500

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	Available Parameters
	00060 Discharge(Mean)
	00065 Gage height(Mean)

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

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USGS Water-Year Summary 2023

09421500 Colorado River Below Hoover Dam, AZ-NV

LOCATION - Lat 36°00'55", long 114°44'16" referenced to North American Datum of 1927, in SW 1/4 NE 1/4 sec.03, T.30 N., R.23 W., Clark County, NV, Hydrologic Unit 15030101, on right bank, 0.75 mi downstream of Hoover Dam.

DRAINAGE AREA - 171,700 mi². including 3,959 mi² in Great Divide basin in southern Wyoming, which is noncontributing (previously considered part of the Missouri River basin).

SURFACE-WATER RECORDS

PERIOD OF RECORD - Oct. 2018 to current year, gage height records. Oct. 1933 to Sep. 2018, gage height and daily discharge records (prior to Apr. 1934, monthly discharge only, published in WSP 1313). Published as "near Willow Beach" 1933-39 and as "below Boulder Dam" 1939-45.

GAGE - Stage recorder. Prior to Oct. 2018, acoustical velocity meters on each turbine in Hoover Dam. Prior to Nov. 1, 1939, water-stage recorder at site 9 mi downstream at datum 594.8 ft above National Geodetic Vertical Datum of 1929, from topographic map. Nov. 1, 1939, to Jun. 30, 1958, water-stage recorder at site 0.8 mi downstream at datum 600.35 ft above NGVD of 1929. Jul. 1, 1958, to Nov. 7, 1979, totalizing flowmeter on each turbine.

COOPERATION - Daily-discharge data provided by Bureau of Reclamation, Boulder City, Nevada until Sep. 2018.

REMARKS - Flow regulated by Hoover Dam on Lake Mead since Feb. 1, 1935. Many diversions above station.

EXTREMES FOR PERIOD OF RECORD - Maximum daily discharge, 50,800 ft³/s, Jul. 29, 1983, no flow at Hoover Dam part of Feb. 10, 1935; minimum daily, 152 ft³/s, Feb. 10, 1935.

WATER-QUALITY RECORDS

PERIOD OF RECORD - Water years 1940 to 2016.

PERIOD OF DAILY RECORD - CHEMICAL ANALYSES: Oct. 1939 to Sep. 1944, Oct. 1950 to Sep. 1957, Oct. 1967 to Mar. 1970. SPECIFIC CONDUCTANCE: Oct. 1939 to Jul. 1957, Oct. 1977 to Sep. 1987. WATER TEMPERATURE: Oct. 1941 to Jul. 1957, Oct. 1977 to Sep. 1987.

REMARKS - Samples collected at gaging station 0.3 mi downstream from Hoover Dam. Unpublished chemical analyses for period Oct. 1939 to Sep. 1940 available from the U.S. Geological Survey in Tucson, Arizona. Surrogate constituent values (parameters 90640, 91063, 91065, 99958, 99959, 99994, and 99995) are recovery percentages for the indicated compounds. These compounds are added to the sample to determine the relative recovery of other organic compounds that are detected using the same analytical method.

EXTREMES FOR PERIOD OF DAILY RECORD - (Since Oct. 1977) SPECIFIC CONDUCTANCE: Maximum, 1,180 microsiemens, cm, Jun. 10, 1980; minimum, 787 microsiemens, cm, Apr. 20, 1987. WATER TEMPERATURE: Maximum, 21.5°C, Jul. 23, 1983; minimum, 9.0°C, Jan. 10, 1978.