Saturday, January 29, 2011

Las Vegas: The next Anasazi Ruin?

Lake Mead, which now supplies the Las Vegas Valley with 90% of its water, has dropped 128 vertical feet since January 2000, and is now at roughtly 43% of capacity (I track these data monthly and drop them into Excel, from which I generate the above graph). It came back up 4 feet in December 2010, owing mainly to severe and sustained west coast and Rocky Mts watershed rains and snows, but, will likely again continue to decline. I shot the photos below in June 2009. The lake has dropped another 9 feet net since then.

When my wife and I relocated to Las Vegas in 1992, 1/3rd of the area's water came from the Spring Mountains watershed to the west of the valley, but the western watershed groundwater levels comprising that resource have declined significantly as well (for the most part owing to our sustained drought and -- until recently -- intense population influx). Below, Lake Mead at Hoover Dam during happier hydrological times.

In response to the dramatic lake level decline, the Southern Nevada Water Authority has proffered a plan to construct a pipeline into Lake Mead via which to obtain water from the northern rural ranching and mountain areas of eastern Nevada along the Utah border. But, the political pushback against this proposal has proved quite formidable. Critics call it another "Owens Valley" debacle, arguing that rural Nevadans (and nearby rural Utah residents). should not be sacrificed for the benefit of even more Las Vegas urban growth just to further enrich developers and the gaming industry.

Clark County, NV (the greater Las Vegas metropolitan area) is now home to some 2 million residents.

It is, long-term, an ecologically unsustainable region, and, absent gaming, would likely be another (perhaps slightly larger) Barstow -- one more dessicated, hardscrabble truck and rail stop of 30 to 40,000 people along the route between Los Angeles and Salt Lake City. Everything is brought in here by truck, rail, or aircraft. With the exception of water (for now).


AN EXCELLENT SERIES FROM THE LAS VEGAS SUN

[Click above to go to the story]
"Las Vegas was first settled for its springs, springs that made it an oasis in the desert. Although those springs have decades since run dry, water is still the most import resource to Las Vegas and the dry Southwest.

And by all indications the region is only going to get dryer. Scientists predict devastating effects from global warming, conservationists are calling for a halt to growth in Southern Nevada as a way to preserve supplies and water managers are looking to ever more creative ways to reduce reliance on the overburdened Colorado River. A Colorado River reservoir at Lake Mead is the source of 90 percent of the valley's water supply. Water levels there have fallen steadily for nearly a decade..."
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DESALINATION TO THE RESCUE?

Consider some attributes of sea water.



One acre-foot of sea water (325,851.4 gallons) weighs roughly 1,390 tons and contains about 40 tons of salt, and another 7 tons of lesser chemical constituents. The technologies for transforming salt water into potable fresh water are relatively mundane (albeit energy intensive). A net 96,500 acre-feet of potable desal water (100,000 acre-feet less the brine constituents) could serve perhaps 300,000 household per year. But, beyond the KwH energy cost of production, there would remain [1] the considerable expense of transporting it to the destinations of need, and [2] environmentally benign disposition of the 4.76 million tons of the residual chemicals (mainly salt), which are typically simply slurried back into the oceans proximate to the desalination plants.

You can just to a little transport arithmetic starting with a gallon of fresh water (post-desal processing) at 8.35 lbs: equivalently ~1360 tons per acre-foot. Use the rough rail freight shipping estimate of a nickel per ton-mile. Haul it 300 miles. About 20 grand, plus the cost of desal production. Pretty expensive alternative to the natural (and, of late in the west, chronically inadequate) hydro cycle.


Given that pipeline pumping of desalinated water several hundred miles up to higher elevations such as Las Vegas (2,160 ft above sea level) is a non-starter (as would be the use of rail tank cars; we don't have enough for just this singular "rolling pipeline" purpose), trade-off/diversion proposals have been floated in recent years in which Nevada would fund additional desal capacity in California in return for diversion of an equivalent volume of downhill-flow water from the Sierra Nevada range watershed inventory. But, myriad California agricultural, environmental, and energy concerns have thus far sufficed to stifle such initiatives. 
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BARCELONA'S DROUGHT

News from May 2008:

Spain's worst drought in decades has forced the city of Barcelona to begin shipping in drinking water in an unprecedented effort to avoid water restrictions.

For the first time ever, tankers began to deliver desperately needed drinking water to the parched region of five million people. Incredibly, Spain has seen almost no rain in the last eighteen months. Water levels have dropped so low in local reservoirs that a long forgotten medieval village has emerged from beneath a rapidly drying lake.

Sixty six tankers are expected to deliver water over the next few months. Meanwhile the Spanish government appears to have given up relying on rainwater. They are now constructing a desalination plant that will supply 60 billion litres of water a year to the parched region.


 

2015 UPDATE
California drought: Can railroads come to the rescue?

(CNBC) As California's four-year drought worsens and water supplies dwindle in the state, an old technology—railroads—could play a role in alleviating some water shortages.

"We certainly have that capability today," said Mike Trevino, a spokesman for privately held BNSF Railway, which operates one of the largest freight railroad networks in North America. "We carry chlorine, for example. We carry liquefied commodities."
Experts say the East Coast's plentiful water could cost cents per gallon to Californians and provide a stable, potable water supply for small communities. Obstacles include identifying a state willing to share some of its water, and securing the construction funds for key infrastructure work, including terminals that can handle water....
See also my KHIT post "Upstream, downstream; what happens to health when there IS no more stream?"
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More to come...