MILWAUKEE — Crack open a beer and what ripples out is 95 percent water.
Water quality determines taste. Water is why beer ads tend to mythologize springs, glaciers and aquifers. It's why the MillerCoors brewery in Milwaukee ranks as the biggest user of water in the metro region.
Yet the vast preponderance of water that creates a "cold one" isn't added at the brewery. Rather, it irrigates the fields that produce beer's next most critical ingredient: barley.
Today, MillerCoors, along with others in the water-intensive brewing industry, is confirming what scientists and environmentalists already figured out: The golden age of cheap, seemingly limitless supplies of fresh water is at an end, even in the world's most developed nations.
"No water, no beer," said Kim Marotta, who oversees water policies at MillerCoors.
An internal inventory following the 2008 joint venture that combined the U.S. operations of SAB Miller and Molson Coors revealed that three of the venture's eight major U.S. breweries -- those in central Texas, southern California and the flagship Coors facility in Colorado — rely on water sources that were already at risk of being overstretched.
The internal audit didn't stop at the breweries. It also found that many of the barley farmers who supply MillerCoors operate in water-stressed regions of Colorado, Montana, Idaho and Wyoming.
"Barley is to beer as grapes is to wine," Marotta said.
So MillerCoors began implementing water conservation strategies at its breweries — not just those deemed most vulnerable, but even in water-abundant Milwaukee. It added valves, sensors and systems that reduce water use. It reorganized workers into "sustainability councils," joined forces with nonprofits such as the Nature Conservancy and moved to the front lines of the conservation crusade.
Also, because the nonwater 5 percent of a beer — the barley and hops — requires torrentially more water to grow and malt than what's added at the brewery, the brewer became enmeshed in agriculture and crop irrigation methods.
It takes 300 barrels of water on average to produce a single barrel of beer, with only three or four of those barrels added at a modern, efficient brewery.
The growing and malting of barley thrust Marotta's water-sustainability teams into the heart of the most serious water issue that confronts any economy: Agriculture guzzles far more fresh water than all homes, industries, swimming pools and golf courses combined. Inefficient irrigation, such as the jumbo center-pivot systems that douse indiscriminately in circular patterns and pump heavily from underground aquifers, accounts for agriculture's biggest water wasters.
In 2011, MillerCoors turned a barley farm in southern Idaho, one of its biggest suppliers, into a showcase of smart irrigation. The brewer gave a grant of nearly $1 million to the Nature Conservancy, whose irrigation experts transformed the 5,000-acre farm at the headwaters of Silver Creek into a testing ground for conservation technologies. They installed soil sensors with GPS satellite connections and smartphone apps, all designed to add water efficiently and only as needed. They redesigned the spigots and valves on the long arms of center-pivot devices for more-precise irrigation that also reduces evaporation waste.
The farm saved 270 million gallons in its first two years, enough to supply one of the large MillerCoors breweries for two months. Using the same model, MillerCoors has begun to introduce its watershed management toolkit to other barley farms in the most distressed areas of Colorado, Montana and Wyoming.
Most notable among them is the troubled San Luis valley of Colorado, a major agricultural basin and home to 150 malt barley growers who supply MillerCoors, including one farm directly owned by Coors. San Luis valley farmers have overpumped the valley's groundwater for decades, in an area without regular rainfall.
MillerCoors' efforts are sure to spill into other industries, experts say.
Since 1950, the world population has doubled. In that same span, water demand has tripled as farmers intensify efforts to feed those populations, industries expand, middle-class affluence spreads in developing countries, and data centers and Internet server farms multiply and need to be cooled. The United Nations projects that by 2030 nearly half of the world's population could face a scarcity of water, with demand outstripping supply by 40 percent.
"It's an inevitability that industries in general are going to have to take water conservation more seriously and ignore their own water consumption at their own peril," said Russell McLendon, an environmental anthropologist and science editor at Mother Nature Network, a leading environmental website. "Water is becoming more expensive in general."
The U.S. has avoided the most severe of the world's water bottlenecks so far. But a study by the Natural Resources Defense Council, a centrist environmental nonprofit group, predicts that 1,100 counties -- one-third of the lower 48 states -- will face higher risks of shortages by midcentury.
"More than 400 of these counties will face extremely high risks of water shortages," it said.
Many breweries have already made strides in lowering water use, according to the Brewers Association, a U.S. brewing trade group.
A little more than a decade ago, the average brewery needed seven barrels of water to make one barrel of beer, including water to cool equipment and rinse kettles (but not including the exponential volumes used to nourish crops). Most breweries today are around a 5-to-1 ratio, with MillerCoors doing better than the industry average. MillerCoors breweries range from its most efficient in Eden, N.C., at 3.1 barrels of water per barrel of beer, to its highest in Golden, at 4.1 barrels of water.
Water conservation efforts also are underway at Anheuser-Busch InBev, brewer of Budweiser, Stella Artois and Guinness, the only U.S. brewing group bigger than MillerCoors. Anheuser-Busch has cut its water use by 19 percent since 2009, according to its website.
Brewers overseas are equally protective of their water supplies. In Germany, the ancestral homeland of Milwaukee's brewery barons, the national brewery trade association rallied last year to defeat legislation that would have allowed hydraulic fracturing, a process of injecting water, chemicals and sand underground to pressure out oil and natural gas. The association, the Deutscher Brauer-Bund, feared that "fracking" could endanger underground water supplies and argued that it would violate the nation's 500-year-old beer purity laws.
In the U.S., a group of more than three dozen craft brewers launched a campaign last year to support new provisions meant to enable the U.S. Environmental Protection Agency to better enforce clean water laws.
Recent court decisions have undermined the EPA's watchdog role, they argue. Calling themselves Brewers for Clean Water and sponsored by the Natural Resources Defense Council, they are pressing Congress and the White House on new laws to safeguard water quality.
But an equally big challenge remains the prevailing mentality of many Americans, said Karen Hobbs, senior analyst for water policy at the Natural Resources Defense Council and lead organizer of the brewers' group.
"We turn on the tap and expect there to be clean water," Hobbs said. "We take it for granted."