LOCATION.--Lat 43° 34'51", long 111° 44'31" (NAD27), in NW1/4 NW1/4 sec.22, T.3 N., R.40 E., Bonneville County, Poplar quad., Hydrologic Unit 17040205, at control tower of Ririe Dam on Willow Creek, 3.4 mi southeast of Ririe, and at mile 20.5.

DRAINAGE AREA.--487 mi², excluding area above Grays Lake outlet.

PERIOD OF RECORD.--January to September 1976, October 1977 to September 1978, October 1986 to September 2000 (discontinued).

GAGE.--Water-stage recorder. Datum of gage is NGVD of 1929 (levels by U.S. Army corps of Engineers).

REMARKS.--Reservoir is formed by rock-faced earthfill dam. Some storage began in July 1974. Usable storage for flood control and irrigation began in January 1976. Total capacity is 100,000 acre-ft between elevations 4,997.0 ft, invert of outlet conduit, and 5,118.7 ft. A conservation and sediment pool stores approximately 10,000 acre-ft below 5,023 ft. Release is controlled by two slide gates discharging into a 12-ft diameter outlet conduit; capacity 1,900 ft³/s. Spillway crest is at elevation 5,093 ft, controlled by two gates.

COOPERATION.--Capacity table furnished by U.S. Army Corps of Engineers.

EXTREMES FOR PERIOD OF RECORD.--Maximum contents, 82,200 acre-ft May 25, 26, 1993, May 18, 1997, elevation 5,113.90 ft; minimum contents, after storage began in January 1976, 500 acre-ft Sept. 30, 1976, elevation, 5,024.40 ft.