As

's experimental desalination plant nears the end of its pilot run, the age-old question of where New Mexico will get enough water to sustain it appears to have some new answers. For some people, anyway.

, the civil engineering professor who heads UNM's

, may not be one of them.

El Paso's Kay Bailey Hutchison Desalination Plant provides the city with 27.5 million gallons of drinking water a day, and Bralley says it's a model for desalination in the West. Only difference: Their water quality's better, and they have river and fresh groundwater sources to limit reliance on desalination alone.El Paso's desalination plant pumps out 27.5 million gallons of drinking water a day. The difference: higher quality saline groundwater, plus backup freshwater.

Thomson calls the desalination pilot “a very useful project; I congratulate Sandoval County planners for having the foresight to undertake this thing.” He says it'll help Sandoval and its surrounding counties—Bernalillo, McKinley and Santa Fe—better understand how much brackish water lies in the ancient aquifer beneath them, how much it'll cost to access that water, and what kinds of treatment methods will be necessary to make it potable.

“It's one of the cutting-edge projects of this type in the Southwest,” Thomson says. But, he adds, “I don't think we should allow residential growth that depends on a non-sustainable water supply.”

For the past two months, Sandoval County's been running a multimillion-dollar desalination pilot project. According to Guy Bralley, the county's water resources administrator, a series of experimental wells, flow tests and chemical tests over the past few years have yielded a more comprehensive (but still incomplete) picture of the 30,000-year-old saltwater aquifer underlying Sandoval and Bernalillo counties: It's extremely salty, with lots of carbonate and some arsenic; it's pretty deep (thousands of feet); its volume is somewhere between half a million and 2.5 million acre-feet.

“It sounds like a lot of water, but it's not,” Bralley says. “You're looking at providing for communities that are the size of Santa Fe or bigger.” He's referring partly to western Rio Rancho, the ever-growing Albuquerque suburb whose expansion depends upon a reliable water supply—and, Thomson notes, a sustainable one, because residential development isn't exactly something that's mobile enough to relocate as soon as the water dries up. The problem with the brackish groundwater in Sandoval County, Thomson says, is that it's not connected to the rest of the rechargeable water system—rivers, fresh groundwater, streams and lakes that refill when rain or snow falls. In this sense, using this water is kind of like using oil instead of solar power (carbon emissions aside).

“The difference in that analogy is that there are alternative energy sources to oil,” Thomson says. “There are no alternatives to water.”

Bralley says the upper estimate for the total volume, 2.5 million acre-feet, would yield enough treated water to support development for approximately 60 years. But Thomson says that's not good enough. “When we plan for new residential growth, we need to talk in terms of sustainability, and that sustainability needs to be in perpetuity,” he says. “It doesn't need to be 30 or 40 or 100 years; it needs to be forever.”

There are other obstacles to using this aquifer, too—things like cost, energy demand and finding a way to dispose of the unwanted salt slurry once it's separated from the purified water. In desalination plants near the coast, salt and minerals can just be returned to the ocean; here, Bralley says he hopes to find some way of either getting someone to buy the stuff for industrial use or of reinjecting it back into the ground. Desalination is also an energy-intensive process, and even the alternative energy options the County touts will require substantial investment in new infrastructure—wind turbines, solar panels, etc. Once a system is in place for extracting, treating and distributing the water (not to mention getting rid of the salt concentrate), Thomson says consumer costs will be significant—four to five times what most New Mexicans pay for treated river water.

“The

—they threaten when they talk about a 5 percent increase,” Thomson says. “Imagine a 500 percent increase!”

Even so, before the 2009 legislature passed a

giving the State Engineer authority over brackish groundwater, Thomson says developers scrambled to lay claim to these kinds of aquifers—because no matter the cost, water in the West is life.

According to Thomson, every one of New Mexico's 16

(Santa Fe County is split between two water regions, Middle Rio Grande and Estancia Basin) mentions water shortage.

“There is no part of this state that has a water surplus that can be readily allocated to address some of these shortages in the municipal areas,” Thomson says. What's more, “New Mexico's no different from Arizona, Colorado, Texas and Utah. The names change, but the problems are identical.”

That, as most hydrologists, water lawyers, environmentalists and raft guides have long known, is more than a little scary, so SFR asked Thomson for his take on the future of the arid West

“We are approaching some natural limits to growth,” he replied. “If there's no jobs, people are going to stop moving here. If there's no water, we won't be able to sell houses. I really think in the next 100 years, we're going to see some limits to development in New Mexico—and whether it's food, water, economy [or] energy, I don't know. I suspect it'll probably be all of those things.”

Then again, maybe

will render the whole water thing moot.

Photo courtesy El Paso Water Utility.