From TheBestLinks.com
 This photograph, taken in the early 1900s before the O'Shaughnessy Dam was contstructed, shows the Hetch Hetchy Valley and the Tuolumne River, looking East. Wapama Falls is on the left, Kolana Rock is on the right. |
 A modern photo, taken from much the same vantage point, shows the submergence of the valley floor under the waters of the reservoir. |
Hetch Hetchy Valley is a glacial canyon in Yosemite National Park in California. It is considered one of the park's greatest scenic wonders, though the lower part is home to the Hetch Hetchy Reservoir. The Tuolumne River flows through the valley.
The highest point in the valley is 2700 feet (800 meters) from the bottom of the valley. There is a hiking trail along the north side of the reservoir, which is a gateway to the northern Yosemite backcountry.
Geography
The Hetch Hetchy Valley runs as a somewhat wavy line from east to west. The Tuolumne River originates in Tuolumne Meadows, just west of the Sierra Nevada's main divide, but the upper part of its route is flat. As it runs west, though, its course deepens markedly as it drops over the first of a string of many waterfalls. After the first few of these, at the confluence with Cold Canyon and Conness Creek, the Hetch Hetchy Valley can be said to begin.
Several parts of the valley merit have garnered names of their own, and one of these is found immediately downriver from here. It is called Glen Aulin (Gaelic: beautiful valley). Here, the valley walls pull away from each other and become steeper. The riverbed is quite level; the water meanders and forms deep pools. Glen Aulin's western terminus is marked by a waterfall.
At this point, Hetch Hetchy Valley enters the mode in which it remains for much of its course. It is a deep, roughly 'V'-shaped gorge. The walls, not as steep and bare as those of Yosemite Valley, Hetch Hetchy's more famous cousin to the south, are sculpted in an almost Baroque richness of form. The flora of the valley bottom is a haphazard melange of chaparral, manzanita scrub and oak woodland characteristic of the foothills and lowlands with a coniferous forest reminiscent of (but different from) that found above the canyon rim. This vegetation clings and clambers up every ledge of the valley walls to the top, giving it a lusher appearance than Yosemite Valley, though this area in fact experiences a drier climate.
Hetch Hetchy Valley, looking west. Muir Gorge runs cuts diagonally across the middleground.
Whereas Yosemite Valley's celebrated waterfalls occur on tributary streams along the sides, most of Hetch Hetchy's lie on the main river itself. Many watercourses do join the Tuolumne River, but their canyons form deep clefts in the Hetch Hetchy's sides and descend to its bottom. The Tuolumne's own bed, beginning even above Glen Aulin, is fashioned as a great staircase punctuated by waterfalls. In the upper valley, even on the relatively level stretches the river tumbles and fumes over piles of boulders. Hetch Hetchy is less deep than Yosemite Valley, but toward the bottom it reaches a depth of roughly a kilometre (3500 feet).
Perhaps the greatest of these waterfalls is Waterwheel Falls, named for a dramatic circular plume of water that appears when the river and the winds run high. A few kilometres below Glen Aulin, the walls of the lower canyon pinch together to form a narrow chasm of less than a kilometre in length, the Muir Gorge. A short way below the Muir Gorge, the Valley widens again, much as it does at Glen Aulin, though here it is deeper. This broad plain bears the name of 'Pate Valley'. Some six km below here, Hetch Hetchy Reservoir claims the Tuolumne River.
The area now inundated by the western portion of the reservoir was originally a flat-bottomed, steep-sided valley like the Pate and Yosemite.
Access
Whereas a road runs up the middle of Yosemite Valley, getting to Hetch Hetchy is more challenging. The Hetch Hetchy Road drops into the valley at the O'Shaughnessy Dam, but all points east of there are roadless, and accessible only to hikers and equestrians.
A trail runs along the Tuolumne River from its headwaters to below Pate Valley (though it leaves the valley floor for some time to avoid the impassable Muir Gorge). It is diligently built, but due to the nature of the terrain it is often rocky, steep and generally difficult. The walking distance from the Tioga Road to the High Sierra camp at Glen Aulin is roughly ten km (six miles). White Wolf campground, southeast of the reservoir, is within day-hiking distance of the canyon rim, but the return trip from the very bottom is long and toilsome. Between the eastern tip of the reservoir and the point where the trail begins the climb to White Wolf, the valley is a trackless wilderness.
History
O'Shaughnessy Dam in Hetch Hetchy
The valley was called 'Hetch Hetchy' as early as the 1860s. The name means either 'acorns' or 'edible seeds' in the Native American Miwok language [1] (http://www.valleywater.org/For_Teachers_and_Students/Teaching_materials/Water_history_teachers_guide/_Name_origin_and_history.shtm). Acorns are indeed available in the valley, but rare elsewhere in the high country.
In 1903, San Francisco applied to the United States Department of the Interior to gain water rights to Hetch Hetchy. This provoked a 10-year environmental struggle with the Sierra Club. The environmentalist John Muir observed:
- Dam Hetch Hetchy! As well dam for water-tanks the people's cathedrals and churches, for no holier temple has ever been consecrated by the heart of man.
Proponents of the dam said that the valley would be even more beautiful with a lake. Muir predicted (correctly) that this lake would deposit an unsightly ring around its perimeter, which would be visible at low water. The struggle ended in 1913, with the passage of the Raker Bill, which permitted flooding of the valley. It is said that the passage of the bill broke Muir's heart: he died the following year. Construction of the dam was finished in 1923.
Geology
Like Yosemite Valley, Hetch Hetchy was also sculpted by glaciers as recent as 10,000 years ago. The more recent glacier there was larger than the one in the paleo-Yosemite Valley. However, today the Hetch Hetchy area is drier.
On the upper portion of the valley beyond the reservoir there is evidence of relatively young lava flows. One recent flow formed the Little Devils Postpile which, as he name suggests, is a smaller version of the Devils Postpile near Mammoth Lakes to the southeast. Both formations are great examples of columnar jointing, a phenomenon that results from contraction of basaltic lava as it cools (forming hexagonal columns).
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