Climate at a Glance: Water Levels – Lake Mead

Hoover Dam and Colorado river forming Lake Mead near Las Vegas, Nevada. Photo by Vichaya Kiatying-Angsulee. Licensed for use by 123RF.

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Bullet-Point Summary:

  • Water levels in Lake Mead rose steadily to record levels between 1965 and 1983, and remained above average through 2002, even as temperatures were rising. After 37 years of abundance, some decline was bound to eventually occur.
  • While there has been below-average precipitation in recent years in the Colorado River basin, most of the nation has enjoyed increasing precipitation as temperatures moderately warm.
  • There will always be some areas of drought in the country, but the overall nationwide trend is more precipitation and less drought. One cannot blame global warming for the few areas of below-average precipitation that remain.
  • The United Nations Intergovernmental Panel on Climate Change (IPCC) confirms there has been an increase in precipitation in the United States, with no detected global precipitation decline. (See https://www.ipcc.ch/site/assets/uploads/sites/2/2019/06/SR15_Chapter3_Low_Res.pdf, pg. 191.)

Short Summary: Even before global warming, some regions of the world experienced periods of lower rainfall and fluctuating river flows and lake levels. During the past century, as shown in Figure 1, below, most of the United States has enjoyed more abundant precipitation as the planet has warmed. As noted elsewhere in Climate at a Glance, Great Lakes water levels and Lake Tahoe water levels have risen and set records in recent years. Lake Mead and its Colorado River source are recent exceptions to this trend, but the overall nationwide trend is still more precipitation and rising lake levels.

For most of the past half century, Lake Mead has enjoyed above-average water levels. Lake Mead water levels rose steadily for 18 years between 1965 and 1983, and remained above average between 1974 and 2002. At some point, a cycle of lower water levels was bound to occur.

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Figure 1: Precipitation has increased throughout most of the United States during the past century as the planet has warmed. Source: National Oceanic and Atmospheric Administration, https://www.ncdc.noaa.gov/monitoring-content/temp-and-precip/us-trends/prcp/trends-prcp-ann-por-full.gif.

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