Researchers dispute cry of ‘worst drought’

Friday, Aug. 13, 2004 | 11:10 a.m.

For months water officials from Southern Nevada and other regions dependent on the Colorado River have been saying that the five-year drought is the worst in 500 years.

Not so fast, a group of researchers is warning. The researchers, among them Thomas Piechota from the University of Nevada, Las Vegas, say it is actually only the seventh worst in the last half-millennium.

Instead of the worst drought coming during the time Christopher Columbus discovered the New World for Europeans, the worst drought came during a 15-year period in the late 1500s -- about two decades before the Pilgrims sailed here on the Mayflower.

And since then, there have been four other droughts more severe, because of their magnitudes or lengths, than the one we are in now, the analysis indicates.

What makes the current drought seem worse is the human impact on the river system, the scientists have found.

"The current drought is amplified by increased water demand due to population growth in the Southwest," Piechota and his co-authors said in EOS, a publication of the American Geophysical Union. "This highlights the importance of evaluating all the possible causes of a decreased water supply.

"A mild hydrologic drought combined with the overuse of water supply can cause extreme drought conditions in a basin," he said. "The current drought is bad, but it could be worse."

Officials with the Southern Nevada Water Authority have warned that five years of drought could lead to cutbacks in the region's allocation from Lake Mead, the huge reservoir on the Colorado River that supplies 90 percent of Southern Nevada's needs. In response to the drought, they have accelerated efforts to drill wells and build pipelines to bring groundwater to the region.

They also have raised water rates and imposed conservation measures on residents and businesses throughout urban Clark County, measures that have provoked reactions from some water users who insist that the answer to the drought is to stop building new homes.

"What happens if this drought continues? What are we going to do?" asked Ray Isner, organizing director for Teamsters Local 631. The union local, which has tried largely without success to organize workers in the booming residential construction industry, has been among the groups and individuals asking for controls on new home growth.

"All we're trying to do is get a handle on it," he said. "Where is all the water going to come from?"

Piechota said the point of the study is not to say people should avoid living in the Southwest. However, it raises a couple of issues that people might want to think about, he said.

Piechota said one important point is that this drought could get a lot worse. Five of the six droughts he looked at lasted a decade or more -- twice as long as the crushing drought we are in now.

Those calling it the worst in 500 years aren't looking at the length of time, he said, but the relative magnitude. Piechota said today's drought could reach the status of worst drought in 500 years or more, but hasn't yet.

The magnitude, however, is already very severe, he said.

"A lot depends on how you analyze the data," Piechota said.

His team looked at tree rings and contemporary river flow data. The demand on water has caused the river system to drop faster and farther than it would have naturally, he noted.

"If you use Lake Mead as your indicator of what kind of drought you're in, there are two factors you have to include: climate conditions over the last several years and the demand by the lower basin users," he said.

Piechota said one of the things people need to do is decide how to use the water that is available, understanding that there will be dry periods.

"It highlights the fact that in this lower (Colorado River) basin that we're operating in, that you have a really fixed amount of water and that the uses have to be critically evaluated," he said. "What is the most beneficial use. Is it growing crops or is it using it for urban areas?"

Although the cities of Nevada and Arizona are using larger amounts of the Colorado River, agriculture such as winter vegetables, cotton and alfalfa still takes more than 70 percent of the lower basin's allocation.

"It's not necessarily the urban users," he said. "It's just the demand on the system."

Piechota said the look at drought issues emphasizes the importance of conservation all along the river system.

"I think it's conservation from everyone," he said. "In our area there has been a lot of conservation with the removal of turf. That's had a big impact."

Vince Alberta, a spokesman for the water authority, said the study looks at the drought issue in a new way, but doesn't invalidate the work the agency has done to encourage conservation.

"The drought is requiring everybody to take a step back and evaluate how and where water is being used, how efficient is that use and what is the economic return on that use," he said. That would include taking a look at agricultural uses.

But the region, which takes less than 5 percent of the total allocated to Arizona, Nevada and California, still needs to be mindful of threats to the river, he said.

"Conservation is always going to be important for this community and all the communities along the Colorado River system," Alberta said.

He noted that water authority chief Pat Mulroy and her deputies were in Northern Nevada Wednesday in an ongoing effort to bring more groundwater for use in Las Vegas.

"One of the things the drought has reinforced, that we had planned years ago, is to diversify our portfolio (of water resources) which will insulate us from future droughts," Alberta said.

The conservation efforts have allowed Southern Nevada to continue its population growth while staying within the limits of water use set by the federal government. Alberta said new population growth will do little to impact the totals as long as irrigation for the new growth is limited.

Water used indoors, he noted, is nearly all treated and returned to Lake Mead, where it does not count against Southern Nevada's total allocation.

"The way houses are being built now it has very little impact on the net use of water," he said. "If you have a limited amount of turf, then the impact on the actual net water supply is very minimal."

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