Las Vegas has already received more than twice as much rain as it saw all of last year, but 2010 has been a disappointingly dry year so far where it matters most to the local water supply.
The below-average snow accumulation in parts of the Rocky Mountains will mean another dry year for the Colorado River, according to the latest report from federal forecasters.
This year’s snowpack is now projected to deliver 5 million acre-feet of water or just 63 percent of the river’s average flow.
That will mean additional declines for Lake Mead, where the water level already has dropped 114 feet in the past 10 years.
Current estimates by the U.S. Bureau of Reclamation predict that by October, the surface of the lake could slip another 20 feet to a level not seen since the summer of 1937, when the reservoir was filling for the first time.
In November, forecasters said there was a 50-50 chance of strong enough flows in the Colorado to allow for the release of surplus water from Lake Powell to Lake Mead.
But while winter storms fueled by the El Niño weather phenomenon dumped rain and snow across Southern Nevada and much of the Southwest, the mountains of western Colorado and Wyoming remained abnormally dry. The Colorado River gets about 85 percent of its water from the snow that typically collects in those two areas.
With only a month or so left in the snow season, forecasters now give just a 3 percent chance that Lake Powell will fill enough to release extra water downstream.
“We’re getting late enough in the season that most of our snowpack is on the ground now,” said Angus Goodbody, federal water supply forecaster based in Portland, Ore. “Where we are now, it’s really almost impossible to get things back up to average for this season.”
Las Vegas water officials have gotten used to such bleak forecasts. Since the current drought took hold in 2000, the Colorado has flowed at about two-thirds of its 30-year average.
J.C. Davis is spokesman for the Southern Nevada Water Authority, the wholesale supplier for a Las Vegas Valley that gets 90 percent of its water from the Colorado River.
“Everybody thinks that we’re joking when we say we hope for the best but plan for the worst,” Davis said. “The fact is that’s the way you have to play it when you’re in the business of municipal water.”
Today, the surface of Lake Mead stands at about 1,100 feet above sea level. The bureau’s projections have it sinking below 1,082 by September. One of the two pipes the authority uses to draw water from the lake will stop working at elevation 1,050.
That’s why the authority is rushing to construct a third straw capable of drawing water from deeper in the lake. The $700 million project is slated for completion in 2013.
Las Vegas has received 3.24 inches of precipitation so far this year. The valley’s official rainfall total for all 2009 was 1.59 inches, roughly half of which fell during the first four months of the year.
All the rain and snow in the Southwest has helped Lake Mead to some extent, said Bob Walsh, spokesman for the Bureau of Reclamation in Boulder City.
Thanks to the steady stream of storms earlier this year, farms in Southern California and Southern Arizona were able to cut their Colorado River orders and leave about five feet of water in Lake Mead that was otherwise set for delivery downstream.
If Lake Mead’s fate is to fall some more, at least it will do so from a higher starting point, Walsh said.
Contact reporter Henry Brean at firstname.lastname@example.org or 702-383-0350.