LOCATION.--Lat 42° 52'39", long 111° 56'40"(Rev.)(NAD83), in SW1/4 SW1/4 SW1/4 sec.19, T.6 S., R.39 E., Caribou County, Hydrologic Unit 17040208, Chesterfield Reservoir quad., at outlet of reservoir on Portneuf River, 2.5 mi northwest of Chesterfield. Also known as "Portneuf-Marsh Valley Reservoir" and/or "Chesterfield Reservoir".

DRAINAGE AREA.--100 mi².

PERIOD OF RECORD.--October 1979 to July 1988 (fragmentary) (discontinued).

GAGE.--Nonrecording gage, sloping gage on dam face. Datum of gage is 5,630 ft above NGVD of 1929, levels by Portneuf-Marsh Valley Canal Co.

REMARKS.--Reservoir is formed by earthfill, rock-faced dam. The dam was completed in 1911, with a capacity of 16,400 acre-ft. In 1951, the dam was enlarged and the capacity was increased to 24,000 acre-ft. Flow from the reservoir is regulated by gates at the outlet control house. Elevation of the crest of the spillway is 5,681 ft. Dam is owned and operated by the Portneuf-Marsh Valley Canal Co. Reservoir is used for flood control and to store water for irrigation in Portneuf River Valley.

EXTREMES FOR PERIOD OF RECORD.--Maximum gage height observed, 46.10 ft, May 19, 1984; minimum observed, 13.10 ft, Sept. 23, 1987.