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.