It's a late March morning, and a light breeze tousles the tops of aspens and Ponderosa pines at Elk Cabin, one of the oldest spots in New Mexico for recording the depth of winter snow. Richard Armijo, a measuring stick in hand, is there to gauge this spring's snowpack.
The site, in the Sangre de Cristo Mountains, sits just upstream from two reservoirs that serve the city of Santa Fe. In late March, Elk Cabin should have a foot of snow on the ground, but it's nearly bare.
Like much of the West, New Mexico has endured a long drought.
According to the latest scientific evidence, such dry spells are likely to grow more severe – as they will around the world. Global warming, climate scientists say, is changing climates from the Himalayan Mountains to the Euphrates-Tigris River Basin. Patterns of rain and snowfall are shifting significantly.
The question now becomes: How will nations and individuals adapt as Earth's climate warms? Glaciers from the Andes to the Alps are shrinking at an accelerating pace. Countries are already haggling over river rights. From 400 million to as many as 3.2 billion people face serious water shortages over the next 20 to 50 years. New Mexico, an already dry region that is getting drier, is on the front lines.
Mr. Armijo, a snow surveyor for the US Department of Agriculture, knows something is going on. Like much of the American West, the state has been in the grip of drought for years.
"We've set record lows for snowpack a couple of times in the last five or six years," he says. "For the most part, the snowpack's gone. In the last three to four weeks, we've experienced some really warm temperatures."
In early February, the UN released a report on the science behind global warming. In it, researchers expressed "very high confidence" that greenhouse-gas emissions – mostly carbon dioxide from burning coal, oil, and natural gas – have been warming the climate.
If these emissions continue to grow at their current rates, the report estimates, global average temperatures could top their 1980-2000 average by 2.3 to 4.1 degrees C. (4.1 to 7.4 degrees F.) by the end of the century. Among the warming's effects: Arid regions will dry out further. And some of the water that they do receive will come in the wrong form (rain instead of snow) or at the wrong time.
On April 6 the UN-sponsored Intergovernmental Panel on Climate Change (IPCC) will release the second of its four major global-warming reports due this year. The focus: the challenges that vulnerable regions are likely to face and their options for adapting.
The new IPCC report is expected to pay close attention to warming's impact on water resources – and for good reason, says James McCarthy, professor of biological oceanography at Harvard University and past co-chairman of the 2001 IPCC working group. In the last five years, scientists have seen "a consistent record" showing a pattern of droughts alternating with strong downpours "with less opportunity for that moisture to be absorbed or retained," Dr. McCarthy says.
A city slakes its thirst
How will humans cope with a drier climate? The city of Albuquerque has shown how much water can be saved through a concerted effort – if resources are available. But its experience also highlights the complex demands made on water resources.
The state's major river, the Rio Grande, cuts through Albuquerque. But it's only a dry riverbed part of the year. The city draws virtually all of its water from an underground aquifer, says John Stomp III, water resources manager for the city. By some accounts, Albuquerque once was thought to be sitting atop an aquifer with enough fresh water to fill Lake Michigan.
But in 1993, a closer look reversed that verdict: The city's underground lake was far smaller than previously estimated – and it was disappearing fast.
In 1994, the city set a goal to cut water consumption by 30 percent over 10 years. By 2004, it had cut consumption by 33 percent. By 2014, it aims to reduce that to 40 percent below 1994 levels.
To meet its goals, the city tightened its building code to improve efficient use of water. It gave tax rebates to residents and businesses for each low-flow toilet or shower head installed in existing buildings. It offered a $100 credit for installing water-efficient washing machines. It gave rebates for xeriscaping – replacing water-hungry lawns and plants with drought-tolerant species – and it changed landscaping codes to require this approach in new developments. The city also irrigates its parks and other public lands with treated municipal wastewater and has been hunting down and repairing leaky water mains.
Sending water back underground
Albuquerque also has built a diversion dam across the Rio Grande and is completing an enormous water-distribution facility nearby. Both open for business next year.
When they do, the city will rely on river water for 70 percent of its needs and use the underground aquifer to make up for shortfalls during dry years. During wet years, it plans to use some of the Rio Grande water to recharge the aquifer.
While the new IPCC reports may begin to add new urgency to water planning, up until now it's been difficult to factor global warming into water-resource plans, Mr. Stomp says.
The earlier models he's relied upon have given conflicting answers to questions surrounding local precipitation.
"One says there's going to be more snow; one says there's going to be less snow," he says. But planning for severe, prolonged droughts has always been part of the planning process, he says.
Over the long term, population growth is likely to push other water-saving approaches to the fore, such as desalination of brackish underground water and reuse of municipal wastewater for drinking. At least six cities in the state are considering wastewater-to-drinking-water conversions either through a direct treatment and recycling system or by using treated wastewater to recharge aquifers.
Ironically, such efforts could make it more difficult for the state to balance the competing demands of its urban and rural interests. It will also be harder to meet its obligations to send some of its river water on to Texas, says John D'Antonio, New Mexico's state engineer.
In the West, agriculture consumes most of the water. Many farmers here are installing more-efficient irrigation systems that lose less water to seepage as it moves along irrigation ditches. But that "leaking" water also contributes to groundwater reserves. Now less water is finding its way back into aquifers.
Water is a finite resource, Mr. D'Antonio notes. If rivers are full subscribed, the only way for the state to grow is to transfer water rights in an orderly way from agriculture to urban uses.
A thirsty world responds to scarcity
How issues like these will play out around the world will depend on many factors, including whether countries can work out disputes over water resources.
So far, the record is patchy. In the Philippines, researchers from Columbia University are trying to help the city of Manila set up a water-leasing deal with nearby farmers. The city and farmers share a small reservoir – and recurring drought.
But in dry years, the city typically has just taken all the water it needed, leading to "massive agricultural losses," says Casey Brown, a member of the group working on the water-lease project. The hope is to set up a plan under which the
city would pay the farmers for the water it takes during droughts – providing, among other things, an added economic incentive for the city to conserve during dry years.
Political instability can get in the way, too.
Iraq, Syria, and Turkey have formed a joint commission on water issues, but it hasn't met since the first Gulf War in 1992, says Olcay Unver, a visiting scholar at the Water Resources Research Institute at Kent State University in Kent, Ohio.
Ironically, global warming may provide a catalyst by forcing countries to work together to solve their mutual problem, he suggests. "All parties see it as a common threat – which it is," Mr. Unver says. "So it could provide the basis for common solutions to water management."
High glaciers retreating fast
Hundreds of millions of people around the world draw their water from major river systems whose sources are mountain glaciers and seasonal snowpack. From the Andes and Himalayas to the Alps, scientists are gathering data that tell a sobering tale of rapidly retreating tongues of ice.
The World Glacier Monitoring Service tracks 27 glaciers in nine mountain ranges around the world. The service's data show that these glaciers have been steadily losing mass since 1980.
This comes as no surprise to Lonnie Thompson. Since 1983 he has studied ice cores from mountain glaciers and ice caps in the Andes, Himalayas, and from Mt. Kilimanjaro in Tanzania. Last July, the Ohio State University professor and his colleagues published a paper suggesting that the current warming at high elevations is unprecedented in the last 2,000 years; in some areas, warming and the pace of glacial retreat is unprecedented for the past 5,200 years.
For example, the Qori Kalis glacier, the largest outlet for the Quelccaya ice cap in Peru, retreated 10 times faster during the 1990s than it did from 1963 to 1978, Dr. Thompson says. "The changes are overwhelming."
If global warming has shifted climate conditions closer to those that existed prior to 5,200 years ago, high-altitude glaciers may be under wholesale retreat and may disappear altogether "in the near future," Thompson says.
Already, some cities relying on these natural water towers are struggling to adapt. But these efforts are at their early stages, according to Walter Vergara, a civil engineer with the World Bank. In Quito, Ecuador, for example, the city of 2 million relies on water from the fast-retreating Antizana glacier. Quito has laid out pipeline and reservoir projects to expand its water supplies to keep pace with the city's growth through 2040. But the plans haven't factored in global warming, Mr. Vergara says.
Quito is now trying to anticipate the glacier's retreat and changing patterns of precipitation. This means extending water pipelines farther up the mountain and around the back of the glacier to tap its eastern, Amazon Basin side. The changes will add $100 million to the $300 million project, Vergara estimates.
Managing water supplies in a warmer, more variable climate "is a challenge developing countries face right now," notes Casey Brown, a climate scientist at Columbia University. "If they can meet this challenge, they'll be in much better shape to meet [the] other challenges [that] climate change brings."