admin
One day a couple of weeks ago, workers on a barge hoisted an 6.9-tonne steel ball — like pulling the plug on a bathtub — and water from Lake Mead in Arizona, flowed into a tunnel that would take it to Las Vegas, 50 kilometres away.
It was the final act in a six-year, US$817-million project designed to provide drinking water for Las Vegas until the end of the century.
Lake Mead and the city of Las Vegas were in trouble. Population growth and a drought that looks as though it might become permanent had the city wondering where it was going to get its water — for drinking, for backyard swimming pools, for fountains at resort hotels along the city’s famed "strip."
The drought, now in its 15th year, has lowered the volume of meltwater that feeds the Colorado River, which ultimately flows into Lake Mead, behind the Hoover Dam. When Lake Mead is full, its surface is about 370 metres above sea level. But it hasn’t been full since 1983.
The water level declined slowly for a while after that. Then, when drought set in in earnest 15 years ago, the decline worsened. By the middle of last year it was down to 330 metres above sea level, and the level is projected to keep dropping.
Photos of the lake, showing a white mineral "bathtub ring" along the cliffs surrounding much of the lake, began to crop up everywhere. It is one thing to say the level is down by about 46 metres in the last 20 years. But it’s startling to see that 46 metres so clearly in photos.
Even more startling is that if the surface level drops below about 305 metres above sea level, the Las Vegas water system would not be able to function. The two intakes now in use would be too shallow.
Tim Barnett, a marine research physicist emeritus at the Scripps Institution of Oceanography in San Diego, did some studies of the situation. The news was not good.
He found it would be difficult to maintain a surface level of at least 305 metres for the water system to keep operating. But he also concluded that climate change would likely decrease the snow meltwater in the Colorado River Basin by up to 30 per cent.
Even a 10 per cent reduction would mean the system would not be able to deliver water by 2040 to all the entities that owned water rights. A drop of 20 per cent would result in a supply shortfall as soon as 2025.
Luckily, the Southern Nevada Water Authority had a tentative plan to construct a third lake intake that would draw water from a point that was 279 metres above sea level. The idea was to reduce levels of sediment and contaminants in the water system. But declining lake levels and the dire predictions of researchers transformed the project from one addressing water quality to one addressing water supply.
That’s the project that ended with the pulling of the plug a couple of weeks ago. But that’s just the first part. It wasn’t originally planned that way, but a recession got in the way. Originally, a new pumping station was to be developed in tandem with the intake. Now it’s slated to go ahead as a second phase of the project.
Work for that involves construction of a shaft six metres wide and 165 metres deep, well shafts, deep-submersible pumps, a motor control centre, and other utility service connections.
That job begins this month. The cost will be another US$650 million, bringing the total for the entire project to something close to US$1.5 billion.
Some of the construction details of the project are worth talking about, which is why I’ll return to the subject next week.
Korky Koroluk is an Ottawa-based freelance writer. Send comments to editor@dailycommercialnews.com.
Recent Comments
comments for this post are closed