Friday, April 09, 2004
Copyright © Las Vegas Review-Journal

Snowmelt forecast 'dismal'

Runoff projections raise possibility stricter water rules just around corner for valley

On a March 11 sampling trip, Mike Gillespie, a snow survey supervisor with the U.S. Department of Agriculture's Natural Resources Conservation Service, weighs a tube filled with snow at Berthoud Summit, on the western slope of the Rocky Mountains. Photo by John Locher. Click image for enlargement. Illustration by Mike Johnson. Tony Tolsdorf, with the U.S. Department of Agriculture's Natural Resources Conservation Service, takes snowpack measurements at Colorado's Berthoud Summit on March 11. Photo by John Locher.

What already was shaping up as another dry year along the Colorado River got significantly worse in March, according to the latest projections by the U.S. Bureau of Reclamation.

Reclamation officials predict the flow of water into Lake Powell will be 55 percent of normal this year, down from the 77 percent of normal that was projected one month earlier.

Because those waters feed into Lake Mead, the primary source of potable water for the Las Vegas Valley, the bleak forecast could mean harsher restrictions on water use are around the corner.

"It's dismal," said David Brandon, hydrologist in charge for the National Weather Service's Colorado Basin River Forecast Center in Salt Lake City. "We kind of got hit with a double whammy. Actually, it was a triple whammy."

March was extremely warm with very little snow accumulation, resulting in a significant amount of early mountain runoff that either evaporated or seeped into ground left dry by five years of record drought, Brandon said.

The Las Vegas Valley gets about 90 percent of its water from the Colorado River system, which is supplied by snow that falls on the western slope of the Rocky Mountains, mostly between January and March.

In a normal year, Lake Powell receives 12 million acre-feet in mountain runoff, roughly 8 million of it between April and July. The current forecast is for 4 million acre-feet during the four peak snowmelt months this year.

"The drought has gotten really serious," said Pat Mulroy, general manager of the Southern Nevada Water Authority. "If it continues like this for a couple more years, Powell could run dry by 2007. You'll be down to mud and sludge at the bottom of the lake."

Barry Wirth, spokesman for the Bureau of Reclamation's Upper Colorado Region, called that an overstatement.

The amount of water in Lake Powell fell to 10.2 million acre-feet this month, 42 percent of the lake's capacity. If the drought continues, Wirth said there is a chance the lake level will fall an additional 93 feet, forcing a shutdown of the turbines that generate power at Glen Canyon Dam.

The lake would have to drop 116 feet beyond that to reach river outlet tubes installed in 1996, a possibility so remote the bureau has never seriously contemplated it, Wirth said.

Below the tubes is 1.87 million acre-feet of water that cannot be released downstream.

One thing is certain: As long as Lake Powell continues to receive below-average runoff, there will be no surplus water available to help refill Lake Mead, which has dropped 75 feet in the past five years.

As a result, Mulroy said the Las Vegas Valley, currently in a drought alert, is just one long, hot summer away from a drought emergency. That designation will come once the surface of Lake Mead dips to 1,125 feet above sea level.

The new, more pessimistic forecast from the Bureau of Reclamation significantly increases the chance that a drought emergency will arrive in January 2005 instead of January 2006, triggering new and more severe water-use restrictions in Southern Nevada, Mulroy said. Those restrictions would include a ban on car washing and mist systems at homes.

And continued drought could prompt other unprecedented action along the Colorado River.

Under agreements stretching back 82 years, the upper basin is required to furnish the three lower basin states with an average of 7.5 million acre-feet of water a year over 10 years. To meet that obligation without emptying Lake Powell, Mulroy and others predict that Colorado, Utah, Wyoming and New Mexico might have to limit water use by some and restrict it altogether for others.

One option Mulroy favors: The major water purveyors in the lower basin would band together and buy temporary, "dry-year options" on the water rights used by farmers, most of them in Southern California and Arizona.

The farmers essentially would be paid not to grow their crops, and the water that would have been used for irrigation would go to municipal water users on an emergency basis, Mulroy said.

Nevada's allotment of Colorado River water is 300,000 acre-feet. California gets 4.4 million acre-feet and Arizona gets 2.8 million acre-feet.

There are 325,829 gallons in an acre-foot. The average Las Vegas Valley household consumes about 230,000 gallons of water per year.

Wirth can't begin to predict how long the drought might last, but he would not be surprised to see it end soon.

"The Colorado is a cyclic river," Wirth said. "I've been with the bureau since 1986, and there have been two droughts and the reservoir has been filled twice."

To recover from the present drought, Brandon said the region needs "quite a few years" of above average snowfall. It would take 16 straight years of average runoff to refill Lake Powell, bureau spokesman Doug Hendricks said.

The amount of water flowing into the lake has been at 62 percent of normal or less in each of the past four years. In 2002, the region's driest year on record, mountain runoff was 25 percent of normal.

The bureau's water forecasts are based on data collected by hundreds of gauges that measure snowpack and precipitation throughout the Colorado River basin.

Bureau computer models show that without Powell's 24.3 million acre-feet of storage capacity, Lake Mead would be nearly empty today because of the drought and the amount of water presently used in the lower basin.