LOCATION.--Lat 44° 25'11", long 111° 23'50" (NAD27), in NE1/4 SE1/4 sec.29, T.13 N., R.43 E., Fremont County, Targhee National Forest, Hydrologic Unit 17040202, Island Park Dam quad., in gatehouse shaft at Island Park Dam on Henrys Fork, 0.5 mi upstream from Buffalo River, 1.3 mi west of Island Park Post Office, and at mile 91.7.

DRAINAGE AREA.--481 mi².

PERIOD OF RECORD.--November 1938 to September 1979, October 1984 to September 1996 (discontinued).

GAGE.--Nonrecording gage. August 9, 1970 to October 23, 1989, water-stage recorder. Prior to August 9, 1976, electric tape gage read once daily. Datum of gage is at mean sea level (levels by U.S. Bureau of Reclamation).

COOPERATION.--Capacity table provided by U.S. Bureau of Reclamation.

EXTREMES FOR PERIOD OF RECORD.--Maximum contents 143,500 acre-ft May 16, 1971, elevation, 6,304.01 ft; minimum after first filling of reservoir in May 1939, 270 acre-ft Sept. 12-25, 1992, elevation, 6,241.45 ft.