Lake Mead

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Lake Mead
Lake Mead & Boulder City.jpg
Location Mohave County, Arizona and Clark County, Nevada
Coordinates 36°15′N 114°23′W / 36.25°N 114.39°W / 36.25; -114.39Coordinates: 36°15′N 114°23′W / 36.25°N 114.39°W / 36.25; -114.39
Lake type Reservoir
Primary inflows Colorado River
Primary outflows Colorado River
Basin countries United States
Max. length 120 mi (190 km)
Surface area 247 sq mi (640 km2)
Max. depth 532 ft (162 m)
Water volume Maximum: 26,134,000 acre·ft (32.236 km3)
Current (September 1): 10,149,000 acre·ft (12.519 km3)
Shore length1 759 mi (1,221 km)
Surface elevation Maximum: 1,229 ft (375 m)
Current (September 1): 1,081.66 ft (329.69 m)
1 Shore length is not a well-defined measure.

Lake Mead is the largest reservoir in the United States in maximum water capacity. It is on the Colorado River about 24 mi (39 km) from the Strip southeast of Las Vegas, Nevada, in the states of Nevada and Arizona. Formed by the Hoover Dam, Lake Mead is 112 miles (180 km) long when the lake is full, has 759 miles (1,221 km) of shoreline, is 532 feet (162 m) at greatest depth, with a surface elevation of 1,221.4 feet (372.3 m) above sea level, and has 247 square miles (640 km2) of surface, and when filled to capacity, 28 million acre feet (35 km3) of water. However, the lake has not fully reached this capacity since 1983 due to a combination of drought and increased water demand.[1][2][3]

History[edit]

Elwood Mead

The lake was named after Elwood Mead (January 16, 1858 – January 26, 1936), who was the commissioner of the U.S. Bureau of Reclamation from 1924 to 1936 during the planning and construction of the Boulder Canyon Project that created the dam and lake. Lake Mead was established as the Boulder Dam Recreation Area in 1936, administrated by the National Park Service. It was then changed to the Lake Mead National Recreation Area in 1964, this time including Lake Mohave and the Shivwits Plateau under its jurisdiction. Both lakes and the surrounding area offer year-round recreation options. The accumulated water from Hoover Dam forced the evacuation of several communities, most notably St. Thomas, Nevada, whose last resident left the town in 1938.[4] The ruins of St. Thomas are sometimes visible when the water level in Lake Mead drops below normal.[4]

At lower water levels, a high-water mark or "bathtub ring" is visible in photos that show the shoreline of Lake Mead. The bathtub ring is white because of the deposition of minerals on previously submerged surfaces.[5]

Geography[edit]

Lake Mead, May 2, 2006
Lake Mead from space, November 1985. North is facing downward to the right. The Colorado River can be seen leading southward away from the lake on the top left. The Hoover Dam is located where the river meets the lake.
The Colorado River flowing into Lake Mead

There are nine main access points to the lake. On the west are three roads from the Las Vegas metropolitan area. Access from the northwest from Interstate 15 is through Valley of Fire State Park and the Moapa River Indian Reservation to the Overton arm of the lake.

The lake is divided into several bodies. The large body closest to the Hoover Dam is Boulder Basin. The narrow channel, which was once known as Boulder Canyon and is now known as The Narrows, connects Boulder Basin to Virgin Basin to the east. The Virgin River and Muddy River empty into the Overton Arm, which is connected to the northern part of the Virgin Basin. The next basin to the east is Temple Basin, and following that is Gregg Basin, which is connected to the Temple Basin by the Virgin Canyon. When the lake levels are high enough, a section of the lake farther upstream from the Gregg Basin is flooded, which includes Grand Wash Bay, the Pearce Ferry Bay and launch ramp, and about 55 miles (89 km) of the Colorado River within the lower Grand Canyon, extending to the foot of 240 Mile Rapids (north of Peach Springs, Arizona). In addition, there are two tiny basins, the Muddy River Inlet and the Virgin River Basin, that are flooded when the lake is high enough where these two rivers flow into the lake. As of now[when?], these basins remain dry.

Jagged mountain ranges surround the lake, offering a startling but beautiful backdrop, especially at sunset. There are two mountain ranges within view of the Boulder Basin, the River Mountains, oriented north-west to south-east and the Muddy Mountains, oriented west to north-east. From the Virgin Basin, you can view the majestic Bonelli Peak towards the east.

Las Vegas Bay is the terminus for the Las Vegas Wash which is the sole outflow from the Las Vegas Valley.

Drought and water usage issues[edit]

Lake Mead as seen from the Hoover Dam clearly showing the white "bathtub ring"

Lake Mead receives the majority of its water from snow melt in the Colorado, Wyoming, and Utah Rocky Mountains. Inflows to the lake are largely moderated by the upstream Glen Canyon Dam, which is required to release 8.23 million acre feet (10.15 km3) of water each year to Lake Mead. Hoover Dam is required to release 9 million acre feet (11 km3) of water each year, with the difference made up by tributaries that join the Colorado below Glen Canyon or flow into Lake Mead. Outflow, which includes evaporation and delivery to Arizona, California, Nevada, and Mexico[6] from Lake Mead are generally in the range of 9.5 to 9.7 million acre feet (11.7 to 12.0 km3), resulting in a net annual deficit of about 1.2 million acre feet (1.5 km3).[7]

Before the filling of Lake Powell (a reservoir of similar size to Lake Mead) behind Glen Canyon Dam, the Colorado River flowed largely unregulated into Lake Mead, making Mead more vulnerable to drought. From 1953 to 1956, the water level fell from 1,200 to 1,085 feet (366 to 331 m). During the filling of Lake Powell from 1963 to 1965, the water level fell from 1,205 to 1,090 feet (367 to 332 m).[8] Multiple wet years from the 1970s to the 1990s filled both lakes to capacity, reaching a record high in the summer of 1983.[9] In these decades prior to 2000, Glen Canyon Dam frequently released more than the required 8.23 million acre feet (10.15 km3) to Lake Mead each year, allowing Lake Mead to maintain a high water level despite releasing significantly more water than it is contracted for. However, since 2000 the Colorado River has experienced persistent drought, with average or above-average conditions only occurring in five years (2005, 2008–2009, 2011 and 2014) in the first fourteen years of the 21st century. Although Glen Canyon was able to meet its required minimum release until 2014, Lake Mead has steadily declined due to the loss of the surplus water that once made up for the annual overdraft.

In June 2010, the lake was at 39 percent of its capacity,[10] and on Nov. 30, 2010 it reached 1,081.94 ft (329.78 m), setting a new record monthly low.[11] From mid May 2011 to January 22, 2012, Lake Mead's water elevation increased from 1,095.5 to 1,134.52 feet (333.91 to 345.80 m), after a heavy snowmelt in the Rocky Mountains prompted the release of an extra 3.3 million acre feet (4.1 km3) from Glen Canyon into Lake Mead.[12]

In 2012 and 2013 the Colorado River basin experienced its worst consecutive water years on record, prompting a low Glen Canyon release in 2014 – the lowest since 1963, during the initial filling of Lake Powell – in the interest of recovering the level of the upstream reservoir, which had fallen to less than 40% capacity as a result of the drought.[13] Consequently, Lake Mead has fallen significantly, reaching a new record low of 1,081.82 feet (329.74 m) on July 10, 2014, with the lake level projected to continue dropping into November 2014.[14]

As a result of the falling water level, marinas and boat launch ramps have either had to be moved to another area of the lake or have closed down completely. The Las Vegas Bay Marina and the Lake Mead Marinas were relocated a few years ago to Hemenway Harbor. Overton Marina has been closed due to low levels in the northern part of the Overton Arm. Government Wash, Las Vegas Bay, and Pearce Ferry boat launch ramps have also been closed. Las Vegas Boat Harbor and Lake Mead Marina in Hemenway Harbor/Horsepower Cove remain open, along with Callville Bay Marina, Echo Bay Marina, Temple Bar Marina, Boulder Launch Area (former location of the Lake Mead Marina) and the South Cove launch ramp.[15]

Changing rainfall patterns, climate variability, high levels of evaporation, reduced snow melt runoff, and current water use patterns are putting pressure on water management resources at Lake Mead as the population relying on it for water and the Hoover Dam for electricity continues to increase. A 2008 paper in Water Resources Research states that at current usage allocation and projected climate trends, there is a 50% chance that live storage in lakes Mead and Powell will be gone by 2021, and that the reservoir could drop below minimum power pool elevation of 1,050 feet (320 m) as early as 2017. Although water levels in the lake rose by more than 30 ft (9.1 m) in 2011 due to a rainy winter and increased snowfall in the Rocky Mountains,[16] it appears highly unlikely that the prevailing pattern of drought will change to precipitation surcharge in a time frame shorter than that in which the lake level will fall below the dead storage level of the downstream diversion and hydro-power intake tunnels.

The diversion tunnels, used during construction, are at an elevation at which the flow of the river would continue indefinitely. But they were permanently sealed with massive concrete plugs, isolating them from the remaining sections of the downstream outlet tunnels when the main dam began to be raised and, later when the lake was filled. Today, it is not very likely that they could be removed from the diversion tunnels.[17][18][19] But, Terry Fulp, manager of the federal bureau office for the lower Colorado, disagreed with the paper, saying that global climate models were not sensitive or refined enough to forecast such effects.[citation needed]

Recreation and marinas[edit]

Lake Mead provides many types of recreation to locals and visitors. Boating is the most popular. Additional activities include fishing, water skiing, swimming and sunbathing. There are four marinas located on the Lake Mead, which include Las Vegas Boat Harbor and Lake Mead Marina (Hemenway Harbor NV) operated by the Gripentogs, Callville Bay (Callville Bay NV) and Temple Bar (Arizona) both operated by Forever Resorts. The area also has many coves with rocky cliffs and sandy beaches. There are several small to medium-sized islands in the lake area depending on the water level. In addition, the Alan Bible Visitor Center hosts the Alan Bible Botanical Garden, a small garden of cactus and other plants native to the Mojave Desert.

B-29 crash[edit]

At the bottom of the lake is a Boeing B-29 Superfortress that crashed in 1948 while testing a prototype missile guidance system known as "suntracker".[20]

The wreckage of at least two smaller airplanes are also within Lake Mead.[21]

See also[edit]

References[edit]

  1. ^ "USGS Circular 1381: A Synthesis of Aquatic Science for Management of Lakes Mead and Mohave". 2012. p. 11. 
  2. ^ Bureau of Reclamation Lake Mead FAQ
  3. ^ Ferrari, Ronald L. (February 2008). "2001 Lake Mead Sedimentation Survey". U.S. Bureau of Reclamation. Retrieved 2012-02-26. 
  4. ^ a b Scott Gold (October 16, 2004). "It's a Historic Drought". Los Angeles Times. Retrieved August 26, 2009. 
  5. ^ Bryan Walsh (December 4, 2008). "Dying for a Drink". TIME (Time Inc.). Retrieved August 26, 2009. 
  6. ^ "Utilization of Waters of the Colorado and Tijuana Rivers and of the Rio Grande: Treaty Between the United States of America and Mexico" (PDF). International Boundary and Water Commission. February 3, 1944. p. 22. 
  7. ^ http://www.cap-az.com/documents/meetings/09-05-2013/12__CR_update_.pdf
  8. ^ http://www.arachnoid.com/NaturalResources/
  9. ^ http://archive.gao.gov/d40t12/122595.pdf
  10. ^ Arizona Game and Fish Department (2010). "Lake Levels/River Flow". Arizona Game and Fish Department. Retrieved June 26, 2010. 
  11. ^ U.S. Department of the Interior, Bureau of Reclamation. "Lake Mead at Hoover Dam, Elevation". Retrieved February 17, 2011. 
  12. ^ http://home.doi.gov/news/pressreleases/Additional-Water-to-be-Released-from-Lake-Powell-to-Lake-Mead-Avoiding-Shortages-in-Lower-Basin-in-2012.cfm
  13. ^ https://wrrc.arizona.edu/forecast-lake-powell
  14. ^ http://www.reviewjournal.com/news/nevada/lake-mead-sinks-record-low
  15. ^ National Park Service
  16. ^ http://www.lasvegassun.com/news/2011/jan/15/water-level-lake-mead-could-rise-thanks-wet-winter/
  17. ^ Barnett TP, and Pierce DW (2008). "When Will Lake Mead go Dry?". Water Resources Research 44 (3): W03201. doi:10.1029/2007WR006704. 
  18. ^ "Lake Mead could be dry by 2021," press release from the American Geophysical Union
  19. ^ Barringer, Felicity (February 13, 2008). "Lake Mead Could Be Within a Few Years of Going Dry, Study Finds". The New York Times. 
  20. ^ "Lake Mead: Exploring the B-29". National Oceanic and Atmospheric Administration. 2007. Retrieved December 1, 2007. 
  21. ^ http://www.8newsnow.com/Global/story.asp?S=416135

External links[edit]