Scripps Institution of Oceanography: Climate Change Means Shortfalls in Colorado River Water Deliveries
EMBARGOED BY PNAS: FOR RELEASE ON Monday, April 20, 2009 02:00 PM PDT: Climate Change Means Shortfalls in Colorado River Water Deliveries: Scripps researchers find that currently scheduled water deliveries from the Colorado River are unlikely to be met if human-caused climate change reduces run1off in the region. The Colorado River system supplies water to tens of millions of people and millions of acres of farmland, and has never experienced a delivery shortage. But if human-caused climate change continues to make the region drier, scheduled deliveries will be missed 60-90 percent of the time by the middle of this century, according to a pair of climate researchers at Scripps Institution of Oceanography, UC San Diego.
“All water-use planning is based on the idea that the next 100 years will be like the last 100,” said Scripps research marine physicist Tim Barnett, a co-author of the report. “We considered the question: Can the river deliver water at the levels currently scheduled if the climate changes as we expect it to. The answer is no.”
Even under conservative climate change scenarios, Barnett and Scripps climate researcher David Pierce found that reductions in the runoff that feeds the Colorado River mean that it could short the Southwest of a half-billion cubic meters (400,000 acre feet) of water per year 40 percent of the time by 2025. (An acre foot of water is typically considered adequate to meet the annual water needs of two households.) By the later part of this century, those numbers double.
The paper, “Sustainable water deliveries from the Colorado River in a changing climate,” appears in the April 20 edition of the journal Proceedings of the National Academy of Sciences.
The analysis follows a 2008 study in which Barnett and Pierce found that Lake Mead, the reservoir on the Colorado River created by Hoover Dam, stood a 50-percent chance of going dry in the next 20 years if the climate changed and no effort was made to preserve a minimum amount of water in the reservoir. The new study assumes instead that enough water would be retained in the reservoir to supply the city of Las Vegas, and examines what delivery cuts would be required to maintain that level.
“People have talked for at least 30 years about the Colorado being oversubscribed but no one ever put a date on it or an amount. That’s what we’ve done,” said Barnett. “Without numbers like this, it’s pretty hard for resource managers to know what to do.”
Barnett and Pierce also point out that lakes Mead and Powell were built during and calibrated to the 20th century, which was one of the wettest in the last 1,200 years. Tree ring records show that typical Colorado River flows are substantially lower, yet 20th Century values are used in most long-term planning of the River. If the Colorado River flow reverts to its long-term average indicated by the tree rings, then currently scheduled water deliveries are even less sustainable.
Barnett and Pierce show that the biggest effects of human-induced climate change will probably be seen during dry, low-delivery years. In most years, delivery shortfalls will be small enough to be manageable through conservation and water transfers, they estimate. But during dry years there is an increasing chance of substantial shortages.
“Fortunately, we can avoid such big shortfalls if the river’s users agree on a way to reduce their average water use,” said Pierce. “If we could do that, the system could stay sustainable further into the future than we estimate currently, even if the climate changes.”
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April 4, 2012, 3:40 pm Uranium, Cattle Grazing and Risks Unknown By LESLIE MACMILLAN Joshua Lott for The New York TimesA cattle ranch near an abandoned uranium mine in Cameron, Ariz. As I reported last weekend in The Times, a cattle rancher stumbled upon an abandoned uranium mine in the summer of 2010 on his grazing land, about 60 miles east of the Grand Canyon on the Navajo reservation, and notified federal officials. They came in with Geiger counters and found levels of radioactivity that were alarmingly high. A year and a half later, the former mine in Cameron, Ariz., is not fenced off to either humans or animals, and cattle continue to roam through the site and eat grass that might be tainted with uranium and other toxic substances.
“Those cattle go to auction in Sun Valley and are sold on the open market,” said Ronald Tohannie, a project manager with the Navajo advocacy group Forgotten People. “Then people eat the meat.”
The owner of Valley Livestock Auction in Sun Valley, Ariz., Derrek Wagoner, confirmed that he buys cattle from the Navajo reservation and is aware that cattle graze on uranium mines there. He added that cattle come to him from all over the Southwest, where there are plenty of former uranium mines.
There is no dispute that beef and milk from those cattle make their way into the food chain. What is not precisely known is how much radioactive material plants absorb through the soil, how much the cattle ingest by grazing on the plants and what the effect might be on humans.
Livestock grazing around the abandoned mines is common throughout the Southwest, according to many environmentalists, scientists, government officials and people in the cattle business. The Colorado Plateau is particularly rich in minerals and in the former mines, which for 40 years supplied crucial materials for the nation’s cold-war nuclear weapons program.
But the effect of the radioactivity on the food chain remains an open question. “There’s just not a lot of data,” said Chris Shuey, an environmental health specialist with the Southwest Research and Information Center. “That’s because mining ended 25 years ago, and the studies ended then, too.”
Yet a resurgence in corporate interest in mining uranium has brought a new wave of studies. In a 2010 report, the Department of the Interior said that proposals for uranium mining at sites adjacent to the Grand Canyon National Park in Arizona had prompted the agency “to investigate physical, chemical, and biological issues potentially affected by mining.”
In January, Interior Secretary Ken Salazar signed a 20-year moratorium on new uranium and other hard-rock mining claims on a million acres of federal land around the Grand Canyon, saying it was needed to preserve the mile-deep canyon and the river that runs through it. The mining industry is challenging that decision in court.
The Interior report summarizes the available findings, saying that although conclusive data is lacking, studies have indicated that toxic substances like uranium and its decay products — including radium and radon — “can affect the survival, growth, and reproduction of plants and animals.” It cited reptiles, birds and “mammalian wildlife that represent essential components of the food web.”
David Shafer, a manager in Colorado for the Department of Energy, one of several federal agencies involved in cleaning up the legacy of cold-war uranium mining on the Navajo reservation, said the Department of Energy was studying how much uranium is absorbed by plants but that its research remained incomplete. “We don’t know what the uptake is,” he said.
“Milk is very stringently tested,” possibly because it is a staple of children’s diets, Mr. Shafer said. “Beef is less so.”
After cattle are auctioned off, they go to various processing facilities where they are butchered and tested for contaminants under U.S.D.A. standards, Mr. Wagoner of the livestock auction company said.
However, federal standards do not include routine screening for toxic chemicals like uranium and its decay products. Standard testing includes biological contaminants like E. coli and salmonella and physical substances like bits of metal that might fall inside a meat grinder. But beef is only spot-checked for chemical contaminants, said Janet McGinn, a senior officer with the U.S.D.A.’s Food Safety and Inspection Service.
When an animal is spot-checked for such substances, it is either because it was chosen as part of a random sampling of the entire population or because it is suspected to be ill.
The lack of data makes some experts uneasy. “We still can’t answer fundamental questions — are there wide population health effects due to uranium mining?” said Mr. Shuey, the environmental health specialist.
“Immune function, kidney disease, high blood pressure — all these things contribute to the burden of ill health” and could be affected by uranium, he said, “but we don’t know for sure.”
“Now there are companies that want to mine uranium again,” he said, “and we’re still a couple of generations away from dealing with the totality of that legacy.”
“We still can’t answer fundamental questions — are there wide population health effects due to uranium mining?”
For people who make a living off the land, tainted cattle is a topic of endless speculation. “They get it in multiple pathways,” said Larry Gordy, the rancher who found the mine on his property and alerted federal officials two years ago. “Cattle eat plants covered with radioactive dust, they breathe in radon, and they drink contaminated water.”
In the arid Southwestern region, water is a precious commodity, and it is collected through various systems throughout the Navajo reservation. Dan Canyon, a former rancher, said that irrigation dams collect water from runoff and some of it comes from former uranium mines, where it can be contaminated by ore tailings.
Standing atop one such dam in Cameron, Ariz., a slope of earth dotted by sagebrush and scored by rivets, Mr. Canyon gestured toward the former mine directly above it. For years, his cattle grazed here.
“I sold my cattle,” he said. “I didn’t want to be responsible for contaminated meat on the market.”
Joshua Lott for The New York TimesLarry Gordy, a Navajo rancher, near the abandoned uranium mine he found on his property in Cameron, Ariz. Federal officials measured high levels of radioactivity there.