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Henry's Lake State Park Trail Guide

About the Trails

The Henry's Lake Trail is divided into two segments, Howard's Slough and Aspen Loop.  Both trails have been designed to enhance the visitors understanding of the natural environment surrounding Henry's Lake.  The trailhead is located in the northeast corner of the Henry's Lake State Park Campgrounds.  The trail system is open to hiking and bicycling only.

Howard Slough

This segment of trail is about 1/2 mile in length (round trip) from the trailhead.  It runs east and west directly above the slough itself.  The trail is paved to allow easy access for all users including wheelchairs.  There are informational panels along the trail, which define the role of the slough; tell how Henry's Lake was formed; and what types of wildlife live in the area.

Aspen Loop

This segment begins near the end of the Howard Slough Trail.  It travels south through open sagebrush and then loops through an alpine forest above the Henry's Lake Outlet,  This trail is a little over 3 miles round trip from the trailhead.  Along the way you will find 9 numbered site posts, which correspond with the interpretive information given below.  The trail is for Intermediate users and has rolling hills and limited steep terrain.

Site Post #1: Stand of Fir Trees - Friend or Foe?

The trees in this stand are Douglas fir.  If you roll a fir needle between your fingers you will notice that it is flat instead of round like a pine needle.  Flattened needles are characteristic of fir trees.

Do you see the moss on these trees?  While it is pretty to look at, this moss is actually a parasite.  It spreads over the branches sucking out moisture and nutrients.  Eventually, the tree will die as the moss spreads over the entire tree.

Site Post #2: Dead Tree = Nature's Recyclers.

This dead tree is the perfect example of recycling in action.  It provides homes for many creatures from insects to cavity-nesting birds such as Idaho's own state bird, the Mountain Bluebird.  Tiny organisms called decomposers are busily consuming and digesting dead wood.  This process releases nutrients such as phosphorus and nitrogen, which are re-used by other plants and trees for growth.  Such natural recycling is a slow process taking 250-2000 years to produce one inch of topsoil.

Site Post #3: Sagebrush.

Do you smell something familiar?  If thoughts of turkey and dressing come to mind then you recognized the familiar smell of sage.  Sagebrush the gray-green shrub you see here was once not as common in the western United States.  Valley floors were covered by a combination of grasses and sagebrush.  Overgrazing of grass by cattle and sheep however, allowed sagebrush to out-compete the native grasses, allowing the sagebrush to take over large areas.  Since livestock do not readily eat the sagebrush, they were moved to new areas where the cycle of overgrazing and subsequent spread of sagebrush was repeated.

Sagebrush is a valuable wildlife food.  Antelope and sage grouse rely heavily on sagebrush year-round white elk, moose, and mule deer browse on it during the winter and early spring.  During hard winters, the availability of sagebrush can mean the difference between survival and starvation for many animals.  Small mammals and birds also benefit from sagebrush for food and shelter.

Site Post #4: Grazing.

Vegetated shorelines along rivers, streams, or lakes care called riparian areas.  A health riparian area is vital for the survival and successful spawning of fish such as trout and salmon.  The clear water these fish need is maintained by the plant roots, which hold the soil, preventing erosion and sedimentation from entering the water.  Overhanging branches provide shade while downed limbs provide shelter.

Health riparian areas can quickly change if livestock are given unrestrictive access.  Prior to 1997, this area was grazed.  Shoreline vegetations quickly vanished, leaving steep dirt sloops.  Fortunately a variety of groups including Idaho State Parks and Recreation, Idaho Fish and Game, Henry's Fork Foundation, local Ranchers, and other groups coordinated their efforts to limit grazing along the shoreline of Henry's Lake.  As  result, the trout reproduction in the lake and watershed has improved significantly.  The fence you see along the hillside allows for grazing, but also allows protection of the riparian habitat as well.

Site Post #5: Sawtelle Peak.

If you look up across the water (southwest), you can see Sawtelle Peak, named after an early settler to this area.  It is possible an extinct volcano over 27 million years old!

Sawtelle Peak has quite a geological history.  The most recent events that impacted the peak occurred during the last ice age, 80,000 years ago.  Glaciers carved the large bowl and U-shaped valleys you see.  They also ground up, moved, and deposited materials at the base of the mountains.  This material is called "Glacial Till".  Accumulations of Glacial Till are often called "Moraines" and make up what you are standing on today.

Site Post #6: Aspen Grove

What do you think is the largest organism in the world?  Would you believe you are standing on it?  That's right - a stand of Aspen Trees.

All these Quaking Aspens you see around you are connected to each other.  The roots from one Aspen sprout and grow in to a new tree.  The roots from that tree sprout and grow into another, and so on.  This seemingly endless process is called "Sucking" and gives Aspen trees a pretty successful survival strategy.

Site Post #7: Henry's Lake Outlet

Before construction of the dam on the outlet, Henry's Lake was only 6 feet deep and had an acreage of 1000 surface acres.  This area was not even part of the lake, but was instead a small flowing stream.

By 1923, a dam was constructed for agricultural irrigation, enlarging Henry's Lake to the size it is today: 12-18 feet deep and 6000 surface acres.  The water in the lake is no longer used for irrigation, except in severe drought years.  The lake is considered a world-class trout fishery as well as a recreational resource.

Site Post #8: Wildlife

This wooded area is home to a variety of wildlife.  Visitors frequently see mule deer.  Pronghorn antelope can be seen in the open sagebrush hills along the edge of the woods.  Other animals to look for include skunk, porcupine, red fox, badger, coyote, elk, moose, and even black bear.

Site Post #9 Birds

Henry's Lake provides a home for a wide variety of birds.  in this area look and listen for songbirds such as the Western Tanager, Mountain Bluebird, Black-capped Chickadee, Dark-eyed, Junco, Stellar's Jay, Olive-sided flycatcher, and Yellow Warbler.  Also watch the tree trunks for the Downy Woodpecker, Hairy Woodpecker, Red-breasted nuthatch and Northern Flicker.