A recent article in the Review-Journal discussed the decline of the Colorado River volume flow and it contained a picture of the "bathtub ring" at the Boulder Basin Las Vegas Boat Harbor at Lake Mead. Approximately how high above current water level is the top of that ring and how long ago was that height achieved? With that in mind, just how much water has Lake Mead lost?
And
Cape Town is in the news recently because the city is about to run out of fresh water. According to published reports, the dams and reservoirs that supply the city with water are down to 28% of capacity, after multiple years of unprecedented drought. The government says that they will shut off the taps and begin rationing on April 21. They're calling it “day zero.” Back in Nevada, there has been lots of talk about the shrinking reserves in Lake Mead. What is the current status of the water supply for Las Vegas? Could Las Vegas be the first North American city to run out of water? Will Las Vegas have a “day zero”?
Christie Vanover, public information office for Lake Mead National Recreational Area, tells us, “The top of the white ring is about 140 feet above the current lake elevation." The last time the lake was at full capacity was in 1983.
As far as losing water is concerned, “Lake Mead is a reservoir that is meant to fluctuate. Over the past 80-plus years, its capacity has varied greatly. Storing more than 3 trillion gallons of water, Lake Mead is currently at 39% capacity, so it's lost nearly two-thirds of its stored water in the past 35 years. However, the demand for water has continued to rise due to growing populations and the need for increased irrigation during the drought of the past 15 years. Many states, cities, and organizations are working hard to increase conservation efforts to help balance out the supply and demand.”
So far, fortunately, there won't be a "day zero" in the foreseeable future. In fact, there's a bit of good news for Lake Mead, which rose from 1,075 feet (above sea level) at the end of 2016 to 1,082 feet at the end of 2017.
Full capacity is 1,220 feet. And as we've written several times in the past couple of years, the 1,075-foot level is critical; if the lake level drops below that, it could trigger a water-shortage declaration, resulting in mandatory water reductions for Nevada, California, Arizona, and Mexico.
We're certainly not out of the woods, as the snowpack is as low this year as it was high last year, due to dry conditions throughout the Southwest that are unusual even for the drought.
Still, the lake has another 75 feet to drop to be in any danger of running out of water, as is currently occurring in South Africa. The Southern Nevada Water Authority’s response has been to dig the so-called “third straw,” which ensures Las Vegas of a water supply should the depth of Lake Mead fall below 1,000 feet. This was an enormous project involving a tunnel-boring machine chewing through solid rock underneath Lake Mead and an intake structure two and a half miles offshore. More than 1,000 concrete truck loads were transported to the intake site on 143 barge trips.
Clearly, the lake has a long way to go to regain even a fraction of the 140 feet it's lost. But it's managing to stay above the shortage level and no shortage is projected for 2018.
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Terrance
Feb-04-2018
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Straski
Feb-04-2018
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