Henrys Fork is a tributary river of the Snake River, approximately 127
miles (204 km) long, in southeastern
in the United
States. It is also referred to as the North Fork of the Snake River.
Its drainage basin is 3,212 square miles (8,320 km2), including
its main tributary, the Teton River. Its mean annual discharge, as
measured at river mile 9.2 (Henrys Fork near Rexburg) by the United
States Geological Survey (USGS), is 2,096 cubic feet per second
(59.4 m3/s), with a maximum daily recorded flow of 79,000 cubic
feet per second (2,240 m3/s), and a minimum of 183 cubic feet per
second (5.18 m3/s).
The river is named for Andrew Henry, who first entered the Snake
River plateau in 1810. Employed by the Missouri Fur Company, he built
Fort Henry on the upper Snake River, near modern St. Anthony, but
abandoned this first American fur post west of the continental divide
the following spring.
Henrys Fork of the
near Coffee Pot Rapids
Kayaking the Coffee Pot Rapids of the Henrys Fork
2 River ecology
3 See also
5 External links
The river's source is at Big Springs and the
Henrys Lake outlet (10
miles northwest of Big Springs). To the east is Targhee Pass, with
Raynolds Pass to the northwest and Red Rock Pass to the southwest. The
headwaters of the Henrys Fork are within 10 miles (16 km) of the
headwaters of the
Missouri River (on the Red Rock River and Madison
River), located across the continental divide in Montana. Henry's Fork
drains the northeastern corner of the
Snake River Plain, along the
Henrys Lake outlet is subject to substantial draw-downs from
irrigation diversions during the summer. Late in the season, as the
draw-downs decrease with the cooler weather, more water is released
into the stream, allowing fish to move up from the lower section of
The Nature Conservancy
The Nature Conservancy sponsors a learning station near the
South of the lake at Big Springs, nearly 500,000 US gallons
(1,900 m3) of constant 52 °F (11 °C) water flow into
the river each day. The river flows south through a high plateau in
northern Fremont County, through the Caribou-Targhee National Forest,
and passes through Island Park Reservoir. It emerges from the
reservoir and flows through a canyon that opens up into a broad, flat
meadow in the
Island Park Caldera
Island Park Caldera in central Fremont County. The river
flows slowly past the town of Island Park, through the Harriman State
Park, otherwise known as the "Railroad Ranch", and then descends
swiftly as it approaches the wall of the caldera, flowing over both
Upper Mesa and Lower Mesa Falls, and emerges from the mountains onto
Snake River Plain near Ashton. It flows southwest across the
plain, past St. Anthony, and splits into multiple channels into a
broad inland delta north of Rexburg. It receives the Teton River from
the east approximately 5 miles (8.0 km) west of Rexburg. It joins
the Snake from the northeast approximately 10 miles (16 km)
southwest of Rexburg, just below 4,800 feet (1,463 m).
Island Park Reservoir, a component of the Minidoka Project, is used
for irrigation in the
Snake River Plain. Its drainage provides one of
the most important rainbow trout fisheries in
Idaho in terms of
habitat, fish populations, and use by anglers. The section of the
river between Henry's Lake and Big Springs is a major spawning area
for trout and is closed to fishing.
Henrys Fork has long been noted for its superb fishing, especially its
dry fly fishing. Bing Lempke, a pipefitter from nearby
was considered the local dean of the fishery, until he died in
Henry's Fork Caldera
List of longest streams of Idaho
Tributaries of the Columbia River
^ Source elevation derived from
Google Earth search using GNIS source
^ a b c "Henrys Fork". Geographic Names Information System. United
States Geological Survey. June 21, 1979. Retrieved July 22,
^ a b "The National Map". National Hydrography Dataset high-resolution
flowline data. U.S. Geological Survey. Archived from the original on
April 5, 2012. Retrieved May 4, 2011.
^ a b "Upper Snake, Headwaters, Closed Basin Subbasins Plan Plan"
(pdf). Northwest Power and Conservation Council. Retrieved October 12,
^ a b "Upper
Snake River basin between Irwin and
Idaho Falls, Water
Resources Data, Idaho, 2005" (pdf). Retrieved October 12, 2011.
^ "Gage 13056500". Retrieved October 12, 2011.
^ Rees, John E. (1918).
Idaho Chronology, Nomenclature, Bibliography.
W.B. Conkey Company. p. 76.
^ Shallat, Todd A.; Bentley, E. B. (1994). Snake: The Plain and Its
People. Boise, ID: Boise State University. p. 125.
ISBN 978-0-932129-12-3. OCLC 31689273.
^ Leavitt, Russell (August 15, 1983). "In Idaho: The Hatch of the
Green Drake". TIME magazine. Retrieved October 12, 2011.
"Henrys Fork Drainage". Graphical Locator. University of Montana. 4
Harvey, Jacqueline (1999). "Henrys Fork Drainage".
Idaho Museum of
Idaho State University.
"Henry's Fork Founda