Las Vegas gets 90 per cent of its water from Lake Mead, the lake created by the Hoover Dam about 45 miles away. It's also a lake that's only half full – with water levels that are decreasing every year. Now the city must dig a massive tunnel that will dip deeper into the lake to ensure Las Vegas's water supply doesn't run out.
A new article in Popular Science explores how officials from the Southern Nevada Water Authority are currently building the "Third Straw" (no, seriously, that is the name) which is pretty much exactly what it sounds like: a huge infrastructural project which will allow them to keep siphoning water from the lake.
A piece of the intake structure, known as the embed, is moved off the delivery truck; the intake structure is currently on a barge in Lake Mead and will be placed on the lake floor
Why is a Third Straw needed? Well, due to a drought lasting 14 years, the First Straw, which has its intake at 1,050 feet (320 metres) above sea level, will be sucking air if water levels drop another 50 feet (15 metres), which could happen as soon as January of 2016. The Second Straw draws a little deeper, but not much, at 1,000 feet (304 metres). The Third Straw is going much deeper, down to 860 feet (260 metres), a level that officials hope will keep Vegas hydrated even if this drought continues.
Digging the Third Straw is a 24-foot-wide (7.2 metres) tunnel boring machine that's currently chewing through the bedrock below Lake Mead. Not only is it one of the largest infrastructure projects ever mounted in the US, due to the quality of the rock and location under the lake, workers are currently digging in the highest-pressure tunnel ever dug on the planet.
Assembling the 600-foot-long (182-metre-long), 24-foot (7.3 metre) diameter TBM; inside the tunnel of Intake No. 3
Although this is the most technologically impressive component of Vegas's water-insurance plan, it's not the only element. As the story explains in detail, Vegas is working hard as a city to decrease its water use with stringent water-use restrictions, hefty fines, and a lawn-buyback programme that pays Las Vegas residents $1.50 per square foot to kill their grass. The Third Straw is buying the city some time, but it will be up to the citizens to make sure they're not left high and dry. [PopSci]
All images via the Southern Nevada Water Authority