• Sunset at Lake Mead's Boulder Basin

    Lake Mead

    National Recreation Area AZ,NV

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  • Important Notice to Mariners

    Lake Mead water elevations will be declining throughout the summer. Before launching, check lake levels, launch ramp conditions, changes to Aids to Navigation and weather conditions by clicking on More »

  • Areas of Park Impacted by Storm Damage

    Strong storms rolled through Lake Mead National Recreation Area Aug. 3-4, causing damage to some areas of the park. Crews are working to restore the below locations. Debris may be present in other areas of the park, as well, especially in the backcountry. More »

  • Goldstrike Canyon, Arizona Hot Spring Trails Temporarily Closed

    A temporary emergency closure is in place for Goldstrike Canyon and Arizona Hot Spring trails within Lake Mead National Recreation Area, through Sept. 11. This closure includes National Park Service and Bureau of Reclamation lands. More »

  • Summer Fire Rules in Effect

    Lake Mead NRA is now enforcing summer fire restrictions. Please click 'more' to learn about the rules for fire during our hot, dry season. More »

Sedimentation Lake Mead

sedimentation-top-image-CMS

After the completion of Hoover Dam in 1935, sediment began accumulating in the new reservoir as the flow of the Colorado River was captured by the rising waters of Lake Mead. Initial estimates were that the new reservoir would last a little over 200 years as it filled with fine silt and sand from the high sediment load carried by the Colorado River. However, revised estimates in 1948 based on new data increased the life expectancy of the reservoir to more than four centuries.

With the completion of Glen Canyon Dam in 1963 upstream of Hoover Dam, sediment volume entering Lake Mead from the Colorado River was reduced to only about a tenth of its previous volume. Much of the sediment is now trapped within Lake Powell behind Glen Canyon Dam. With the reduced sediment input into Lake Mead, the lifetime of the reservoir has been extended to potentially more than a thousand years.

 

Sedimentation


Post-impoundment sediment in Lake Mead is generally distributed along the floors of the deepest parts of the lake, mainly following the paths of the former Colorado River and the tributary valleys that fed into it, rather than being deposited as a drape across the entire lake floor. These sediments are thickest in the deltas that formed at the mouths of the Colorado River and its tributaries, including the Virgin and Muddy Rivers. Maximum sediment thickness exceeds 250 ft where the Colorado River enters Lake Mead, thinning to 50 - 100 feet in thickness along the remainder of the drowned Colorado River channel to Hoover Dam.

Tributary valleys have a thinner sediment cover indicating the Colorado River has been the primary sediment source. Sediments are composed of between 12 and 45 percent sand with the remainder being a mix of clay and silt. Most of the clay and silt has been transported to the deepest parts of the lake by the dense, sediment-laden currents flowing into Lake Mead from the Colorado River. Over time, sediment in the deeper parts of the lake has been compacted as additional sediment has accumulated.

 
Year Reservoir Capacity Rate of Sedimentation Sediment Volume
(acre feet @ 1220') (acre feet/year) (acre feet)
1935 30,944,400 137,000 0
1948 29,878,000 97,429 1,066,400
1963 28,321,300 88,200 2,623,100
2001 28,543,420 < 10,000** 2,400,980*
Notes
* Increase in reservoir capacity and decrease in sediment volume due to significant compaction of sediments in lower elevation portions of the reservoir.
** Decreased rate of sedimentation due to closure of Glen Canyon Dam in 1963.
 

Sedimentation Maps


Sedimentation-General-Map Link to Map Segment 2    Map Segment 3  Map Segment 1
Graphic Source: Las Vegas Sun
 
Sedimentation-Trial-1-HR
Illustration: Anthony Ross
 


 
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References & Resources


 

2001 Lake Mead Sedimentation Survey Bureau of Reclamation, February 2008
http://www.usbr.gov/pmts/sediment/projects/ReservoirSurveys/Reports/2001 Lake Mead Sedimentation Survey.pdf

Comprehensive Survey of Sedimentation in Lake Mead, 1948-49 Geological Survey Professional Paper 295 http://pubs.usgs.gov/pp/0295/report.pdf

Mapping the Floor of Lake Mead (Nevada and Arizona): Preliminary Discussion and GIS Data Release U.S. Geological Survey Open File Report 03-320, 2003 http://pubs.usgs.gov/of/2003/of03-320/

Mapping Lake Mead Geophysical Review, Vol. 31, No. 3, pp. 385-405, July 1941

Surficial Geology of the Floor of Lake Mead (Arizona and Nevada) as Defined by Sidescan-sonar Imagery, Lake Floor Topography and Post-impoundment Sediment Thickness U.S. Geological Survey Open File Report 2009-1150 http://pubs.usgs.gov/of/2009/1150/

The 1963-64 Lake Mead Survey Bureau of Reclamation REC-OCE-70-21 http://www.usbr.gov/pmts/sediment/projects/ReservoirSurveys/Reports/The 1963-64 Lake Mead Survey.pdf

*Note: Calculations and mapping are based on a lake elevation of 1100’.

Surveys were conducted between 1999 and 2001 by the U.S. Geolgocial Survey in collaboration with the Bureau of Reclamation, University of Nevada Las Vegas, and the National Park Service.

Did You Know?

Lake Mead Exotic Plant Management Team

In order to manage invasive plants on park lands, 16 Exotic Plant Management Teams (EPMT's) have been deployed throughout the country. The teams are a new weapon to combat exotic plants. The first test of the EPMT concept was made in 1996 at Lake Mead National Recreation Area. More...