Henrys Fork (Snake River)

Infobox_River
river_name = Henrys Fork (Snake River)


image_size = 200 px
caption = Henrys Fork of the Snake River in Eastern Idaho
Courtesy of Idaho Tourism
origin = Henrys Lake near the Continental divide on the Montana - Idaho border
mouth = Snake River
basin_countries = Idaho United States
length_km =
length_mi = 110
length =
elevation_m =
elevation_ft =
elevation =
mouth_elevation_m =
mouth_elevation_ft =
mouth_elevation =
discharge_m3/s =
discharge_cuft/s = 2096
discharge =
watershed_km2 =
watershed_sqmi = 3212
watershed =

Henrys Fork is a tributary river of the Snake River, approximately 110 mi (177 km) long, in southeastern Idaho in the United States. It is also referred to as the North Fork of the Snake River. Its drainage basin is convert|3212|sqmi|km2, including its main tributary, the Teton River. [http://www.nwcouncil.org/fw/subbasinplanning/uppersnake/plan/Assessment/1IntroOverview.pdf Upper Snake, Headwaters, Closed Basin Subbasins Plan Plan] , Northwest Power and Conservation Council] Its mean annual discharge, as measured at river mile 9.2 by USGS gage 13056500 (Henrys Fork near Rexburg), is convert|2096|cuft/s|sigfig=3, with a maximum daily recorded flow of convert|79000|cuft/s|sigfig=3|abbr=on, and a minimum of convert|183|cuft/s|sigfig=3|abbr=on. [http://pubs.usgs.gov/wdr/2005/wdr-id-05-1/pdf/ID05v1-08.pdf Upper Snake River basin between Irwin and Idaho Falls] , Water Resources Data, Idaho, 2005]

The river is named for Andrew Henry, of the Missouri Fur Company, who first entered the Snake River plateau in 1810. He built Fort Henry on on the upper Snake River, near modern St. Anthony, but abandoned this first American fur post west of the Rocky Mountains the following spring. [cite book
last = Shallat
first = Todd A
coauthors = Bentley, E B
title = Snake: the plain and its people
publisher = Boise State University
date = 1994
location = Boise, ID
pages = 125
oclc = 31689273
isbn = 9780932129123]

ource

The river rises out of Henrys Lake, west of Targhee Pass on the continental divide on the border with Montana. Its headwaters are within 10 mi (16 km) of the headwaters of the Missouri River (on the Red Rock River and Madison River), located across the continental divide in Montana. It drains the northeastern corner of the Snake River Plain along the continental divide.

River ecology

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 river. There is a Nature Conservancy learning station near the outlet stream.

South of the lake at Big Springs, nearly 500,000 U.S. gallons (1,900 m³) of constant 52 degree Fahrenheit (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. Emerging from Island Park Reservoir, the river flows through a canyon that then opens up into a broad, flat meadow located in the 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 the Snake River Plain near Ashton. It flows southwest across the plain, past St. Anthony, splitting into multiple channels into a broad inland delta north of Rexburg. It receives the Teton River from the east approximately 5 mi (8 km) west of Rexburg. It joins the Snake from the northeast approximately 10 mi (16 km) southwest of Rexburg.

Island Park Reservoir 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 Henrys 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 Idaho Falls, was considered the local dean of the fishery, until he died in 1990. [cite journal
last = Leavitt
first = Russell
title = In Idaho: The Hatch of the Green Drake
journal = TIME magazine
volume =
issue =
pages =
publisher =
location =
date = Aug 15, 1983
url = http://www.time.com/time/magazine/article/0,9171,949710,00.html?promoid=google
doi =
id =
accessdate = 2008-08-15]

Maps

References

ee also

*List of Idaho rivers
*Tributaries of the Columbia River

External links

* [http://www.esg.montana.edu/gl/cst/112.00043.450110.58044.78012001560a.html Univ. of Montana: Henrys Fork Drainage]
* [http://imnh.isu.edu/digitalatlas/geog/fishery/drainage/drain29.htm Idaho State University: Henrys Fork Drainage]
*Gnis|383107|Henrys Fork