Friday, Aug. 1, 2008 | 2 a.m.
MORE THAN ONE MODEL
What’s next: The Southern Nevada Water Authority has expert Frank D’Agnese building a model to help predict the environmental effects of pumping ground water out of Snake Valley. Opponents of the Las Vegas pipeline plan also are building a model, as are at least one federal agency and experts testifying for Utah, which also opposes Snake Valley pumping.
Why is Nevada requiring the model now? Deputy State Engineer Jason King said modeling’s role in the debate has changed. His office has hired hydrologists who can make use of new and better technology in creating models. Previous studies also have been done in Snake Valley, meaning data exist about water resources in the valley, King said.
How much water has Las Vegas been granted from other areas? State Engineer Tracy Taylor’s ruling in July granted the Water Authority 19,000 acre-feet of water a year from three rural valleys — Cave, Dry Lake and Delamar. An acre-foot is about 326,000 gallons of water, enough to serve two single-family homes for a year.
Since the big hearings on Southern Nevada’s plan to take water from eastern Nevada’s Great Basin aquifer began, water officials have been able to avoid presenting scientific predictions about how pumping will affect the lifeblood of that region’s ranchers, plants and animals.
But in July, the state official who is deciding how much of that water will be allocated to the Las Vegas Valley ordered the Southern Nevada Water Authority to run complex, computer-based modeling to develop those predictions about Snake Valley.
The results may determine the future of not just urban Clark County, where officials are desperate for more water to sustain unprecedented growth, but also whether the ranching way of life in rural eastern Nevada will continue.
“It has very important implications for all of us” throughout the state, said Launce Rake, a Las Vegas-based spokesman for the Progressive Leadership Alliance of Nevada, a group opposing the pipeline.
The Southern Nevada Water Authority has cast a large net across the Great Basin in search of unclaimed water. It has won water rights from Spring, Cave, Dry Lake and Delamar valleys, and it envisions filling a $3 billion, 250-mile pipeline from the high desert to Las Vegas.
But still up for grabs is the water beneath Snake Valley, a rich agricultural region that straddles the Nevada-Utah state line. Because of the location, Utah has a say in the matter.
On the Nevada side, State Engineer Tracy Taylor decides who gets water and how much. In the case of Snake Valley, Taylor is saying — for the first time — that before he makes a ruling, the Southern Nevada Water Authority must present a model of the basin and make predictions of what will happen over the next 200 years of pumping the valley.
The demand caught Las Vegas water attorneys by surprise at a preliminary hearing in July. During a morning briefing over Snake Valley, attorneys for the Water Authority had argued that the final showdown over its plans to import billions of gallons of water each year from rural parts of the state should begin in January. They had been through it all before and wanted to move forward as quickly as possible.
But their momentum evaporated with the demand for modeling. They promptly changed their tune about the timeline. They said the Water Authority couldn’t prepare a model by summer. With that, the state engineer’s staff members said they would likely postpone hearings until fall 2009.
Longtime observers say Taylor’s decision to require a model probably comes from the increasing comfort with, and expertise at, modeling among his own staff.
“He has now brought on his staff people that are very competent modelers,” said John Bredehoeft, a retired hydrologist who long lobbied Taylor to use modeling. “Without that (expertise) on his own staff, the state engineer was limited with respect to what the models were telling him.”
Without hydrologists on staff, Taylor could only listen to quarreling experts and weigh their testimony.
With the Water Authority’s experts arguing that modeling wasn’t particularly useful as a predictive tool, Taylor seemingly gave little weight to the models done by the protesters, Bredehoeft said.
“He didn’t listen to what we said,” he recalled. “The first time I have really seen him take cognizance of the model was in the Cave, Dry Lake and Delamar decision.”
Still, Taylor’s ruling granted the authority 19,000 acre-feet of water a year from the three rural valleys. An acre-foot is about 326,000 gallons of water, enough to serve two single-family homes for a year.
Jason King, deputy state engineer, agreed the role of modeling has changed.
“Decades ago we didn’t have the expertise,” he said. “We have the staffing; software programs are better. Time has passed so there is more data on water levels and spring flows ... It’s definitely changed the way we can look at those issues.”
King said there is enough data about Snake Valley — enough studies have been done and enough pumping has been performed — that modeling should be reliable there, where it might not be in other valleys.
And although Bredehoeft said he wasn’t sure whether requiring a model would change the course of the Snake Valley hearings next year, he said he thinks it is important for Taylor to have all the information this time around.
Still, experts on both sides admit modeling isn’t absolute.
“No model is perfect,” said Susan Lynn of the Great Basin Water Network, which opposes the pumping plan.
As hearing officer Susan Joseph-Taylor said in July, the state engineer’s office has spent countless hours on “Modeling 101,” which she hopes to skip over in the Snake Valley hearings to get right to the pertinent predictions.
During hearings on Spring Valley’s water in September 2006, an expert witness for the Water Authority discounted the usefulness of modeling altogether. Today that expert — Frank D’Agnese — is building the authority’s new model.
Opponents of the pipeline presented their own models predicting dramatic lowering of the water table. That translates into certain environmental harm, they said.
The Water Authority attempted to punch holes in a model created by Tom Myers, a hydrologist consultant for opponents of the pipeline.
The authority had its own model — a computer program that calculates what will happen to ground water under certain conditions, such as pumping. But the authority didn’t present any predictions gleaned from the model.
It said there weren’t enough data to make reliable predictions with its model.
And Myers didn’t have time to develop predictions from his model.
Simeon Herskovits, an attorney for the opponents, said he has no doubt the Water Authority suppressed what its model showed, which was drawing down the water table over time, during the Spring Valley hearings.
The National Park Service had run the authority’s model — and found that it predicted a drop in the water table with prolonged pumping. But because the federal agency had signed an agreement to not oppose the authority’s water rights applications in Spring Valley in exchange for a role in overseeing pumping, predictions it made from the model weren’t allowed as evidence.
But in hearings in February, the Water Authority was unable to sweep that under the rug, because the scientist and former authority consultant who had prepared it, Tim Durbin, was testifying for the opposition instead — about the grave effects pumping could have.
Durbin could not be reached for this story.
Still, after both sets of hearings, the state engineer granted the authority about half the water it had requested and mandated monitoring programs to report any effects.
Kay Brothers, the authority’s deputy general manager, said last month that the agency has never suppressed evidence.
She also said models are only one tool, and not the most useful one, in determining how much water is available in a valley.
“It concerns me that everyone starts to think that the model is going to tell you exactly what is going to happen,” she said. Modeling, she said, is “not exactly a science.”
The model the authority is required to prepare for federal environmental review, she said, will be useful for providing ranges of pumping’s effects.
But Myers said the new model, which the authority is developing in cooperation with federal agencies, is imperfect for the same reason most models are — the scientists building them just don’t have enough information.
With plenty of pumping and plenty of data, however, a model gets more reliable. And, models are the only predictive tool available to hydrologists.
“Here we are trying to decide whether to allow that pumping, and so you have to make a best guess,” Myers said.
So he’ll present a model next fall. So will at least one federal agency and experts testifying for Utah, which opposes the authority’s plan for Snake Valley.
One thing all the models presented during hearings on the authority’s applications have in common — and something they’re likely to have in common with the models that will be presented next fall — is that they show significant drawdown of the water table, Bredehoeft and Myers said.
What isn’t certain is just how low it will go, and how long it will take to get there.
But to the plants, animals and farmers who depend on that water, Myers said, it’s immaterial whether its level drops 120 feet or 200 feet.
“If you’re looking at a spring on the surface, that’s an academic difference,” said Myers. “It’s still a dry spring.”
And if you water your livestock from that spring, as so many ranchers do in Snake Valley, it could be the only thing standing between you and financial ruin.