Hetch Hetchy

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This photograph, taken in the early 1900s before the O'Shaughnessy Dam was constructed, shows the Hetch Hetchy Valley and the Tuolumne River, looking east. Wapama Falls is on the left, Kolana Rock 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 is the name of a valley, a reservoir, and a water system in California. The valley lies in the northwest corner of Yosemite National Park, and is currently completely flooded by the 312-foot (95 m)-high[1] O'Shaughnessy Dam. The dam is a curved gravity dam and is named for former San Francisco chief engineer and the original chief engineer of the Hetch Hetchy Project Michael M. O'Shaughnessy. The dam creates Hetch Hetchy Reservoir, with a capacity of 360,000 acre·ft (440,000 ML).[1] The water in the reservoir is delivered by the Hetch Hetchy Aqueduct system to San Francisco and its client municipalities in the greater San Francisco Bay Area. The system, completed in 1934, is a 167-mile (269 km)-long gravity-driven network of dams, reservoirs, tunnels, aqueducts and pipelines that delivers 31,900,000 cubic feet (900,000 m3/d) of water per day. The creation of the reservoir and water system remains controversial to the present day.

Contents

Geography [edit]

The reservoir is filled by the Tuolumne River. Upstream from the valley lies the Grand Canyon of the Tuolumne. 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. The O'Shaughnessy Dam is near Yosemite's western boundary, but the long, narrow, fingerlike reservoir stretches eastward for about 8 miles (13 km).[1]

Tueeulala Falls on the north side of the valley.

Wapama Falls 1,700 feet (520 m) and Tueeulala Falls 840 feet (260 m), both among the tallest waterfalls in North America, are both located in Hetch Hetchy Valley.[2]

Flora and fauna [edit]

Hetch Hetchy is home to a diverse array of plants and animals. Gray pine, incense-cedar, and California black oak grow in abundance. Many examples of red-barked manzanita can be seen along the Hetch Hetchy Road. Spring and early summer bring wildflowers including lupine, wallflower, monkey flower, and buttercup. Seventeen species of bats inhabit the Hetch Hetchy area, including the largest North American bat, the western mastiff.[2]

History [edit]

The name "Hetch Hetchy" comes from the Native American Sierra Miwok language and refers to a grass with edible seeds that grows in the valley.[3] It was first used[citation needed] by Joseph Screech, who in 1850 became the first non-Native American to enter the valley. Screech noted that Paiutes[3] had formerly inhabited Hetch Hetchy and still gathered seeds, roots and acorns in and around the valley. Acorns are available in the valley, but are rare elsewhere in the high country.

Hetch Hetchy Little Arroyo in 1908

In 1867 Charles F. Hoffmann of the California Geological Survey conducted the first survey of the valley.[4]

Damming [edit]

O'Shaughnessy Dam
O'Shaughnessy Dam.jpg
O'Shaughnessy Dam in Hetch Hetchy Valley
Country United States
Location Hetch Hetchy Valley, Yosemite National Park, Tuolumne County, California
Coordinates 37°56′51″N 119°47′17″W / 37.94750°N 119.78806°W / 37.94750; -119.78806Coordinates: 37°56′51″N 119°47′17″W / 37.94750°N 119.78806°W / 37.94750; -119.78806[5]
Construction began 1915
Opening date 1923
Dam and spillways
Type of dam Concrete thick arch-gravity
Height 312 ft (95 m)[1]
Length 910 ft (280 m)[1]
Volume 675,000 cu yd (516,000 m3)
Impounds Tuolumne River
Spillways 1
Type of spillway Overflow, 4x drum gates
Spillway capacity 30,000 cu ft/s (850 m3/s)
Reservoir
Creates Hetch Hetchy Reservoir
Capacity 360,000 acre·ft (0.44 km3)[1]
Catchment area 459 sq mi (1,190 km2)
Surface area 1,972 acres (798 ha)
Max. water depth 306 ft (93 m)[1]
Power station
Type Multiple including Moccasin #1 and #2 and Robert C. Kirkwood powerhouses
Hydraulic head 1,500 ft (460 m)
Installed capacity 218 MW[6]

In 1906, after a major earthquake, San Francisco applied to the United States Department of the Interior to gain water rights to Hetch Hetchy. This provoked a seven-year environmental struggle with the environmental group Sierra Club, led by John Muir. Muir observed:[7]

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 replied that the valley would be even more beautiful with a lake. Muir correctly predicted this lake would deposit an unsightly ring around its perimeter, which would inevitably be visible at low water.

Since the valley was within Yosemite National Park, an act of Congress was needed to authorize the project. In 1913, the U.S. Congress passed and Woodrow Wilson signed the Raker Act, which permitted the flooding of the valley.

Construction of the dam was finished in 1923. The dam height was then 227 feet (69 m) high; its present height of 312 feet (95 m) was achieved only later in 1938. The Early Intake (Lower Cherry) Powerhouse began commercial operation five years before the O'Shaughnessy Dam was completed. The first Moccasin Powerhouse in Moccasin, California began commercial operation in 1925 followed by the Cherry Powerhouse in 1960 (the same month the Early Intake Powerhouse was taken out of service). In 1967 the Robert C. Kirkwood Powerhouse started commercial operation followed by a New Moccasin Powerhouse in 1969 when the Old Moccasin Powerhouse was taken out of service. Finally, in 1988, a third generator was added to the Kirkwood Powerhouse.[8]

Water and power [edit]

Hetch Hetchy is owned by the City and County of San Francisco and is operated and maintained by the San Francisco Public Utilities Commission. The reservoir's primary purpose is to supply drinking water and electric power to 2.4 million people in the San Francisco Bay Area. It is one of nine reservoirs in San Francisco's system and holds about 25% of its overall water storage capacity. The reservoir sits on federal land, for which San Francisco pays a lease of $30,000 per year.[9][10]

Hydroelectricity is produced by Kirkwood and Moccasin Powerhouses, which have capacities of 118 and 100 megawatts, respectively.[6]

Because Hetch Hetchy is a municipal water supply, and its water is not filtered, swimming and boating are prohibited. The water flows from the reservoir into the aqueduct that travels across the Central Valley. Upon reaching the Bay Area, the aqueduct splits into four separate Bay Division pipelines at the point where it reaches the city of Fremont. These are called Bay Division Pipelines (BDPL) 1, 2, 3, and 4, with nominal pipeline diameters of 60, 66, 78, and 60 inches (1.5, 1.7, 2.0 and 2.4 m, respectively). All four pipelines cross the Hayward fault. Pipelines 1 and 2 cross the San Francisco Bay to the south of the Dumbarton Bridge. Pipelines 3 and 4 run to the south of the bay.

One of the pipelines ends at the Pulgas Water Temple, which is a small park that contains classical architectural elements that celebrate the water delivery.

Aqueduct infrastructure [edit]

Hetch Hetchy Aqueduct
Hetch Hetchy Aqueduct
Begins Tuolumne River
37°51′09″N 119°59′30″W / 37.852425°N 119.991572°W / 37.852425; -119.991572
Ends Crystal Springs Reservoir
37°29′01″N 122°18′59″W / 37.483508°N 122.316306°W / 37.483508; -122.316306
Maintained by San Francisco Public Utilities Commission
Length 167 mi (269 km)
Capacity 905,000 m3 (734 acre·ft) per day
Construction began 1914
Opening date 24 October 1934
References: U.S. Geological Survey Geographic Names Information System: . Note that map above only shows Bay Area portion of aqueduct.
Reservoirs
Power generation
  • Robert C. Kirkwood Powerhouse
  • Dion R. Holm Powerhouse

Proposed restoration [edit]

The Raker Act specified that because the source of the water and power was on public land, no private profit could be derived from the development. One local weekly newspaper says the city of San Francisco is in violation of the law, but according to Peter Byrne, "the plain language of the Raker Act itself and experts who are familiar with the act (and have no stake in city politics) all agree: The city of San Francisco is not in violation of the Raker Act."[11] Harold L. Ickes, Secretary of the Interior in the late 1930s, said there was a violation of the Raker Act, but he and the city reached a final solution in 1945.[12]

The Sierra Club currently advocates removing the dam, but the city of San Francisco wants to keep it because the reservoir currently serves 2.4 million people, including parts of San Mateo County, Alameda County, and Silicon Valley. Deconstructing the dam would cost $3 billion-$9.8 billion, according to a study ordered by Governor Arnold Schwarzenegger.[13]

In 1987, the idea of razing the O'Shaughnessy Dam gained an adherent in Don Hodel, then Secretary of the Department of the Interior under President Ronald Reagan. Hodel called for a study of the effect of tearing down the dam. The National Park Service concluded that two years after draining the valley, grasses would cover most of its floor and within 10 years, clumps of cone-bearing trees and some oaks would take root. Within 50 years, vegetative cover would be complete except for exposed rocky areas. In this unmanaged scenario, where nature is left to take hold in the valley, eventually a forest would grow, rather than the meadow being restored. However, the same NPS study also finds that with intensive management, an outcome in which "the entire valley would appear much as it did before construction of the reservoir" is feasible.[14]

Tuolumne River below Hetch Hetchy dam

Some observers, such as Carl Pope (Director of the Sierra Club), stated that Hodel had political motives [15] in proposing the study. The imputed motive was to divide the environmental movement: to see residents of the strongly Democratic city of San Francisco coming out against an environmental issue. Dianne Feinstein, the mayor of San Francisco at the time, said in a Los Angeles Times story in 1987: "All this is for an expanded campground?... It's dumb, dumb, dumb." Hodel, now retired, is still a strong proponent of restoring Hetch Hetchy Valley and now-Senator Feinstein is still strongly against restoration. The George W. Bush administration proposed allocating $7 million to studying the removal of the dam in the 2007 budget. Dianne Feinstein opposed this allocation, saying, "I will do all I can to make sure it isn't included in the final bill. We're not going to remove this dam, and the funding is unnecessary."[16]

In November 2012, San Francisco voters soundly rejected Proposition F,[17] which would have required the City to conduct an $8 million study on how the flooded valley could be drained and restored to its former state. The proposed study would also have been required to identify potential replacements for the water storage capacity and hydroelectric power production.[18]

See also [edit]

Wikimedia Commons has media related to: Hetch Hetchy
View of reservoir and Kolana Rock

References [edit]

  1. ^ a b c d e f g "Hetch Hetchy". San Francisco Water Power Sewer. Retrieved 2013-05-23. 
  2. ^ a b  This article incorporates public domain material from the National Park Service document "Hetch Hetchy Valley" (retrieved on 2013-05-23).
  3. ^ a b Farquhar, Francis P. (1926). "Place Names of the High Sierra". Retrieved 2006-09-09. 
  4. ^ Hoffman, C. F. (1868). "Notes on Hetch-Hetchy Valley". Retrieved 2006-09-09. 
  5. ^ "O'Shaughnessy Dam". Geographic Names Information System, U.S. Geological Survey. 2000-06-14. Retrieved 2011-01-06. 
  6. ^ a b "Power Plants of California". California Energy Almanac. Retrieved 2013-05-23. 
  7. ^ Muir, John (1912). "The Yosemite". Retrieved 2006-09-09. 
  8. ^ "Chronology of San Francisco's Water Development". Retrieved 2010-09-23. 
  9. ^ Upton, John (6 January 2012). "Water From Yosemite Is Still Cheap, for Now". The New York Times. p. 21A. Retrieved 21 May 2013. 
  10. ^ Righter 2005, p. 241.
  11. ^ Byrne, Peter (2001-04-04). "Delusions of Power". San Francisco Weekly. 
  12. ^ Righter 2005, p. 185.
  13. ^ "Hetch Hetchy Restoration Study". California Department of Water Resources. Retrieved 2008-06-03. 
  14. ^ Riegelhuth, Richard; Botti, S., Keay, J. "Alternatives for restoration of Hetch Hetchy Valley following removal of the dam and reservoir page 15". 
  15. ^ Undamming Hetch Hetchy by Carl Pope - Restore Hetch Hetchy
  16. ^ Doyle, Michael (2007-02-08). "Hetch Hetchy debate reborn". Sacramento Bee. 
  17. ^ "San Francisco Department of Elections, November 2012 Results". Retrieved 29 November 2012. 
  18. ^ Wildermuth, John (2012-11-10). "Hetch Hetchy fight not over, activists say". San Francisco Examiner. 

External links [edit]

Portal icon San Francisco Bay Area portal
Hetch Hetchy Reservoir
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