Virtual Field Trip (Spring Break 2007)

Hoover Dam Hydroelectric facility Located on the Colorado River on the Arizona/Nevada Border Construction started in 1931 Dam was completed in 1935 two years ahead of schedule and under budget! http://www.sdsuniverse.info/story.asp?id=3713 http://www.usbr.gov/lc/hooverdam/service/index.html

Dam Data Arch Gravity Dam 726 feet tall 1244 ft long 45 ft wide at the top 660 ft wide at the bottom 3.25 million cubic yards of Concrete

Bird’s Eye View

Power plant Facts The power plant at the base of the Dam has 17 Commercial generating units. (shown on next slide) Capable of generating 2080 Megawatts

Nevada Wing with 8 Generators

Schematic of the Dam

There are 4 intake towers 2 on the Arizona side and 2 on the Nevada side.

How power is Generated Water passes through screens on the intake towers and flows through the penstocks (30 ft in Diameter) to the generators falling an average of 420 feet. (head) Water reaches a speed of 85 mph by the time it reaches the generators. http://en.wikipedia.org/wiki/Hoover_Dam

Water from the Penstock turns a shaft on the generators. Rotors, made up of electromagnets, are connected to the shaft and spin around a coil of copper wire, generating an electric current.

Hoover Dam Can Generate 2080 Megawatts

Transmission Lines Lines Deliver power to NV, AZ and CA

Lake Mead Flooded The Black Canyon of the Colorado River Covers 247 mi 2 Popular recreation spot for boating, fishing and water sports Flooded many small communities including St. Thomas NV. White bathtub ring marks the 1983 high water mark result of the 1982-3 El Niño

Before the Dam: Black Canyon http://www.library.unlv.edu/early_las_vegas/hoover_dam/short/0015_0020t.jpg

St. Thomas Founded by Thomas Smith, a Mormon settler in 1865. The town was a farming and business community until 1938 when the area was flooded by Hoover Dam, as Lake Mead filled. http://www.nps.gov/archive/lame/stthomas.html

Diverting the River http://www.usbr.gov/lc/hooverdam/images/p45-300-02371.jpg

Construction at Night, July 1934 To learn more about the Construction of Hoover Dam visit this website: http://www.ecommcode.com/hoover/hooveronline/hoover_dam/const/toc.html

Endangered Fish At least two species of fish have had a major decline since the construction of Hover Dam, the Razorback Sucker (right) and the Bonytail (left)

Bonytail This fish was listed as endangered in 1980. There are no known breeding populations left in the wild. Reintroduction is happening through stocking in the areas shown on the map.

Razorback Sucker This fish is limited to 25% of its original range. Most of the population consists of adults due to low survival rates of young fish. The hump on the fishes back provides stability in turbulent water.

Reasons for decline Alteration of the Colorado River system from a turbulent river to a series of calm reservoirs and channelized reaches Nurseries of the fish have been flooded Dams block upstream migration Non-native sport fish Lack of warm seasonal flow, water from the dams is always cold. Other introduced animals, plants, pathogens and contaminants.

Information on Endangered Fish http://mountain-prairie.fws.gov/ea/infopackets/coloradoriver/CRRPfacts.pdf http://mountain-prairie.fws.gov/ea/infopackets/coloradoriver/ http://biology.usgs.gov/s+t/imagefiles/r166f03.htm http://biology.usgs.gov/s+t/noframe/r166.htm http://heritage.nv.gov/images/2003/gilele80.jpg

Downstream Water in the Colorado River is always cold Flooding no longer scours the banks and exotic species such as tamarisk have become common Fertile silt in no longer deposited during floods