Sunday, October 10, 2004
Copyright © Las Vegas Review-Journal

Valley has two water savings accounts

Local providers have been socking away water since 1987

J.C. Davis, spokesman for the Southern Nevada Water Authority, stands next to a well at the water authority's North Well Field on Valley View Drive. The pumps draw groundwater to supplement what the valley gets from the Colorado River. Photo by Jane Kalinowsky Click image for enlargement. Graphic by Mike Johnson.

It's a warm fall day, neck deep in the worst drought on record, and the pumps are churning at the Southern Nevada Water Authority's North Well Field on Valley View Drive.

At the moment, and throughout the hottest part of the year when water use is at its peak, the pumps are being used to draw groundwater to supplement what the valley gets from the Colorado River.

Soon, however, that flow will be reversed, and over the next six months or so several billion gallons of treated drinking water from Lake Mead will be pumped directly into the ground.

That may sound like a reckless waste, but it's really the opposite.

Since 1987, local water providers have socked away 275,000 acre-feet of water using a process called artificial recharge. About 13,000 acre-feet was injected into the ground during the first three months of this year. Another 17,000 acre-feet is due to be pumped down by year's end.

An acre-foot is 325,851 gallons, roughly the amount of water consumed by the average Las Vegas Valley household every 17 months.

"A lot of the public is not even aware that we've been squirreling away water for years," said J.C. Davis, spokesman for the water authority. "It's important they understand that we aren't operating without a net."

It is called the Southern Nevada Groundwater Bank, but local water officials didn't invent it. They only gave it a name.

The storage area itself has been here far longer than people have, trapping melted snow from the past 10,000 winters in a 1,000-square-mile matrix of dirt and rock generally found 500 to 1,200 feet below the surface.

Now the valley's principal aquifer is being used much like a common savings account.

Each year, Nevada is allowed to consume 300,000 acre-feet of water from the Colorado, minus any surplus water that might be available during wet years. Any portion of the 300,000 acre-feet that isn't used goes into the bank, so the less water the valley consumes, the more it can save.

"It's a two-for," said Pat Mulroy, water authority general manager. "The community creates a drought cushion for itself by conserving.

"There in that bank is the water we might need in a protracted drought."

And in the use-it-or-lose-it world of water law, artificial recharge allows Nevada to get the full benefit from its comparatively meager share of the river, even when the water is not immediately needed to meet demand.

The practice is nothing new. Artificial recharge has been around for thousands of years, helping humans grow crops and survive in arid climates from ancient Persia to 1930s California.

Arizona, a state almost entirely dependent on its groundwater supplies, began large-scale banking 10 years ago and has put away more than 1.8 million acre-feet so far.

Artificial recharge also is used to stabilize and replenish areas where groundwater has been overpumped, causing the earth to subside and wells to fail. Over the past three years, the Las Vegas Valley Groundwater Management Program has injected more than 7,000 acre-feet of water into selected parts of the valley for just that purpose.

"Most people forget that aquifers are finite, and it takes a long time to replenish them. Nature does that very, very slowly," said Tom Harbour, water planning supervisor for the Central Arizona Project. "With artificial recharge, we're kind of helping nature along."

The water authority and its member agencies operate the largest injection-based artificial recharge system in the world.

The system employs 77 wells, most of them in the northwest part of the valley. Some of the wells are used both to put water into the ground in the fall, winter and spring and take water out in the summer.

On paper, the water authority has yet to make a withdrawal from its bank, though technically at least some of the water put in has been pumped out again by the roughly 9,000 residential and commercial groundwater wells throughout the valley.

"I don't think we'll need to tap the bank for some time. I hope that's the case," said Kay Brothers, the water authority's deputy general manager for engineering and operations.

When the valley is forced to use its bank -- if, for example, the drought reduces the state's Colorado River allocation or local water use surpasses supply before new resources can be tapped elsewhere in the state -- there should be enough water put away to supplement what we get from Lake Mead for at least a decade, Brothers said.

Then there is Nevada's other water savings account, one forged not by pumps but by policy.

Through a cooperative agreement struck in 2001, the water authority has secured 110,000 acre-feet of credits in Arizona's groundwater bank.

Nevada hasn't had to tap that bank either, but when it does, the only thing flowing from Nevada to Arizona will be money.

Cashing in the credits works like this: Arizona surrenders some of its 2.8 million acre-foot Colorado River allocation to Nevada, which pulls the water from Lake Mead. If necessary, Arizona replaces that water by tapping its groundwater reserves or paying farmers not to irrigate some of their crops. Nevada pays Arizona for any costs associated with pumping and delivering the groundwater Arizona needs to replace the Colorado River water it has given up.

Unlike Nevada's injection-based system of artificial recharge, Arizona benefits from permeable soils that allow the use of spreading basins, which Harbour described as "very, very leaky ponds" that can let up to 7 feet of water seep into the ground each day.

The state also channels water into normally dry streambeds with similar results.

The Central Arizona Project, which channels water 350 miles from the Colorado River to Phoenix, Tucson and farms in between, has five spreading basins in operation, one under construction and another in the design and permitting phase. Water also is banked by the Salt River Project and the Arizona Water Banking Authority.

The agreement between Nevada and Arizona allows the Silver State to bank a total of 1.25 million acre-feet in Arizona through 2050. So far, though, little progress has been made toward that goal because Arizona must first satisfy its own water needs before it can start setting aside water for another state.

Larry Dozier, deputy general manager of the Central Arizona Project, said that by 2016 officials in Arizona hope to have met most of that state's water storage targets and have close to 1 million acre-feet set aside for Nevada.

"The darned river hasn't cooperated," Dozier said. "It got dry, and there hasn't been a lot of surplus water."

The two states are now discussing a way around that. "What we're talking to Arizona about is firming up the 1.2 million acre-feet," Mulroy said.

In effect, the plan being discussed involves Arizona extending Nevada a line of credit.

"We would let them take their water out before they put it in," said Dozier, who sees the idea as a way of building the kind of cooperative spirit long absent from Western water politics. "Our answer is, we think we have the capability to do it, and it's good to have friends when there is a drought on the river."

Dozier added that a number of "policy and political implications" will have to be addressed, but he thinks some kind of agreement could be reached by the end of the year.