Why Wasn't Lake Mead's "Third Straw" Put into Immediate Use?

Given the falling water level in Lake Mead, why wasn't the “third straw” put into immediate use as soon as it was completed? Why did the Southern Nevada Water Authority wait until the second straw was disabled (if that was indeed the case)? Why, instead of digging an entirely new tunnel to the lake, did the SNWA not simply run a pipe from Straw #2 to a lower depth and draw from that?

Bronson Mack of the SNWA takes your questions in order.

“Intake Number Three was immediately put into service once construction was complete. Construction of the deep-water intake was conducted between 2008 and 2015. So since 2015, all of southern Nevada’s Colorado River water has been conveyed through this intake."

Click here to see an informative 30-minute documentary on "one of the world's most challenging tunneling projects, Intake No. 3."

As for the second straw being disabled, Mack says this is a misapprehension.

“To answer this question, we need to clarify that it was Intake Number One and its pumping station (Pumping Station One) that were rendered inoperable when Lake Mead approached elevation 1,050 feet in early April. We also need to establish that the deep-water Intake Number Three was interconnected with the existing Pumping Stations One and Three. This allowed the existing pumping stations to operate while drawing water through Intake Number Three, and while SNWA constructed the Low Lake Level Pumping Station.

“Pumping Station Number Two remains in service and is operable down to elevation 1,000 feet. We will continue to operate this pumping station until water levels approach elevation 1,000 feet. Once that occurs, we will operate the high-lift pumps at the Low Lake Level Pumping Station to replace Pumping Station Number Two, just like we did to replace Pumping Station One on April 1.”

Circling back to your second question, Mack poses his own. “So why did we wait until Pumping Station One was inoperable to operate the Low Lake Level Pumping Station? Hydraulics. The deep pumps in Low Lake Level Pumping Station require more energy to operate than the pumps at Pumping Station One—they are deeper pumps and have to pump the water higher; therefore, it requires more energy. So we maximized the efficiency to consume less power, until lake levels dictated that we needed to transition to the new pumping station.”

Which leaves the query as to why the second straw wasn’t simply extended to a deeper reach.

“We did not extend Intake Number Two, because the pumps associated with that intake can only reach a depth of elevation 1,000 feet. So we needed a deeper intake and a deeper pumping station … hence Intake Number Three and the Low Lake Level Pumping Station."

Here is some more information and a couple of short videos about the Low Lake Level Pumping Station that help illustrate some of this admittedly complicated situation. But we hope you agree that it's good to know the Southern Nevada Water Authority is working to ensure Lake Mead water keeps flowing into Las Vegas taps, even as the lake level has dropped 180 feet over the past nearly 40 years and that a recent 24-month government forecast predicts the lake will drop another 26 feet by September 2023.

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rokgpsman Jun-03-2022

Lake Mead shrinking

Las Vegas does not have a viable backup source of water, it's pretty much dependent on Lake Mead. Since Las Vegas gets nearly all of its water from Lake Mead this shrinking of the lake is probably the single biggest long-term obstacle the city faces for future growth. Water conservation measures will only do so much. The lake's level depends a lot on the weather and that's something humans can't do much about. It's not just that more water is taken from the Lake than is coming into it, the rate of evaporation has increased on the lake's surface and along the length of the Colorado River. Need to start having big snowy winters in the Rocky Mountains once again.

R Geoffrey Jun-03-2022

Refilling the lake

Just this week a few opined on what it would take to refill the lake...

https://www.quora.com/What-naturally-occurring-events-would-it-take-to-fill-Lake-Mead-and-will-that-ever-happen-again

jay Jun-03-2022

Random thought - Build a dome

If your ever stuck in the desert you can dig a hole, put in a canteen, and build a funnel with a black plastic garbage bag. Natural condensation will give you about a half cup of water overnight. Not much but it will keep you alive. 

Lake Mead is huge but if they were to build a structure over top and cover it in lightweight material it would contain the evaporation and perhaps even add a bit of condensate. I suspect it would cost less than any one of the new stadiums being proposed and in typical Vegas fashion you could probably sell tickets to see this engineering marvel being built. 

Not a solution but a good hedge to extend the life. 

Boaters won't be happy... just saying

Kenneth Mytinger Jun-03-2022

We need more snowpack

Kudos to the Water Authority for their planning.  Here's a good graph of recent snow levels in the Upper Colorado Basin.  They're only getting good snow once every few years, while we need several consecutive years of more snowpack.  The snow melt feeds Lake Powell, which releases water downstream to Lake Mead:

http://snowpack.water-data.com/uppercolorado/index.php


More info here:  https://mead.uslakes.info/

Lots of data here:

https://www.nps.gov/lake/learn/nature/storage-capacity-of-lake-mead.htm

https://www.usbr.gov/lc/region/g4000/riverops/hourly7.html

Question of the Day - 03 June 2022

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