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  • UPDATE, 11/9: As of November 8, the USGS has successfully restored all of the operational gages that stopped transmitting due to an issue with the satellite telemetry system that records and transmits data. The USGS will now focus on restoring other equipment that experienced the telemetry issues, including about 85 rapid deployment gages that are used periodically for emergency response. Read more
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LOCATION.--Lat 42° 46'45", long 112° 52'45" (NAD27), in SE1/4 SW1/4 sec.30, T.7 S., R.31 E., Power County, Hydrologic Unit 17040206, American Falls SW quad., at outlet gates near right abutment of American Falls Dam on Snake River at American Falls, and at mile 714.7.

DRAINAGE AREA.--13,580 mi2, excluding indeterminate nontributary area on Snake River Plain.

PERIOD OF RECORD.--March 1926 to September 1979, October 1982 to September 2000 (discontinued).

GAGE.--Water-stage recorder. Datum of gage is sea level, levels by US Bureau of Reclamation. Prior to July 11, 1977, water-stage recorder at same datum on old dam.

REMARKS.--Reservoir is formed by concrete gravity dam and spillway with earth embankments at each end. Dam was rebuilt in 1976 and 1977. Partial storage began in 1926, full storage in 1927. Capacity, 1,700,000 acre-ft, between elevations 4,295.66 ft and 4,354.50 ft. Elevation at bottom of outlet gate is 4,285.00 ft and elevation at top of spillway radial gate is 4,356.50 ft. Dead storage unknown. Water is used for power generation and for irrigation by canals diverting from Snake River at Minidoka and Milner Dams. From 1973-77, because of the condition of the old dam, storage was limited to the spillway crest level, 4,343.2 ft. Reservoir was emptied in September 1977 to permit completion of the new sections of the dam. Storage began on October 14, 1977, behind the present structure.

COOPERATION.--Reservoir elevations and capacity table provided by US Bureau of Reclamation.

EXTREMES FOR PERIOD OF RECORD.--Maximum contents, 1,748,000 acre-ft June 21, 1963, elevation, 4,355.34 ft; minimum since full capacity (excluding 1977), 0.00 acre-ft, Sept. 14-16, 1990, when there were no usable contents because the gates were open and natural flow was passing through the reservoir.


Available Parameters Period of Record
All 1 Available Parameters for this site
00054 Reservoir storage(Obs.) 1926-03-01  2000-09-29

Graph w/ stats
Graph w/ (up to 3) parms
Days  (365)

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Begin date

End date

Summary of all available data for this site
Instantaneous-data availability statement
*** There are no data available on the Waterdata system for the time period specified,
    although data may be available in the files of the local USGS office operating the station.