Tag Archives: Lake Mead

First-ever Lower Colorado River Basin Water Shortage Declaration

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Peter Lobner, updated 17 September 2011

At its maximum capacity, Lake Mead water level is at an elevation of 1,220 feet (372 meters) at the Hoover Dam and holds 9.3 trillion gallons (36 trillion liters) of water. It was last at its maximum capacity in 2000 and has been declining since then as shown in the following graph.

Source: Universe Today, data via US Bureau of Reclamation & NASA

In my 18 June 2021 post, I discussed the Lake Mead water supply for Las Vegas and the alarming trend of decreasing water level in Lake Mead as a result of the persistent drought in the watershed for the Colorado River. 

In July, the Bureau of Reclamation began releasing additional water from reservoirs upstream of Lake Powell (which is upstream of Lake Mead) in an attempt to stabilize the lake level and maintain hydropower generation at the Glen Canyon dam (which forms Lake Powell). 

The following chart shows that the Lake Mead water level was at 1,067.72 feet on 17 August 2021, more than seven feet below the 1,075 foot threshold for triggering a water shortage declaration.  The lake level appears to have temporarily stabilized, possibly benefiting from the increased releases into upstream Lake Powell.

Source: Universe Today, data via US Bureau of Reclamation & NASA

On 16 August 2021, the Bureau of Reclamation issued their much anticipated projection of 2022 operating conditions for Lake Powell and Lake Mead. They reported: 

“Given ongoing historic drought and low runoff conditions in the Colorado River Basin, downstream releases from Glen Canyon Dam and Hoover Dam will be reduced in 2022 due to declining reservoir levels. In the Lower Basin the reductions represent the first “shortage” declaration—demonstrating the severity of the drought and low reservoir conditions.”

The planned actions in response to this first-ever shortage declaration take effect on 1 January 2022, as described in the Bureau’s news release here: https://www.usbr.gov/newsroom/#/news-release/3950

In summary, the following cuts in Colorado River water allocations are expected:

  • Arizona:  Loses 18% of the state’s annual apportionment
  • Nevada:  Loses 7% of the state’s annual apportionment
  • Mexico:  Loses about 5% of the country’s annual allotment

California has more senior water rights than Arizona and Nevada and will be spared immediate cutbacks when they are implemented on 1 January 2022.

Additional cuts in water allocations will be triggered if Lake Mead water level continues to decline to the following thresholds:  1,050 feet, 1,045 feet, and 1,025 feet.

Let’s pray for a lot of wet weather in the US southwest.

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Las Vegas Made a Good Bet on the Third Straw

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Peter Lobner

Las Vegas relies on Lake Mead for 90% of its water needs. Currently, water from Lake Mead can be supplied to Las Vegas by three intakes at different levels in the lake.  The newest, and deepest, is known as the “third straw” intake (IPS-3), which taps into the lake at 860 feet above sea level. That’s 190 feet below the highest existing intake, IPS-1, at 1,050 feet.

The operation of this three-intake system is explained in Southern Nevada Water Authority’s (SNWA) short video, “How does the SNWA’s Low Lake Level Pumping Station protect our drinking water supply?” at the following link: https://www.youtube.com/watch?v=bDDuid6XJnw&t=39s

You’ll find Lake Mead current water level and historical water level data here:  http://mead.uslakes.info/level.asp

On 18 June 2021, the lake level was 1,070.43 feet MSL at 5:00 PM.  This is 158.57 feet below the “full pool” level of 1,229.00 feet and is only 20.43 feet above the highest (IPS-1) intake.

Source: http://mead.uslakes.info/level.asp

On 10 June 2021, Lake Mead water level was 1,071.51 at 7:00 AM and was about 36% full.  The lake had not been this low since July 2016.  Using just the 10 June and 18 June data points, lake water level currently is decreasing at about 1.5 inches per day.

Runoff from the Rocky Mountain snowpack is essentially over this year, so water level is expected to continue declining until the start of the next rainy season in November.

The first-ever official federal water shortage declaration is expected in August 2021, when the Bureau of Reclamation issues its regularly scheduled long-term water level projection.  A Level 1 declaration would be implemented in January 2022 under agreements negotiated with seven states that rely on Colorado River water: Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming. Water from the Colorado River serves 40 million people in these states and Mexico.

Let’s pray for a lot of wet weather in the US southwest.

For more information