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 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 almost overnight, 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 like the Nature Conservancy, and moved to the front lines of the conservation crusade.
Also, because the non-water 5 percent of a beer -- basically, 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.
All told, 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 just about any economy: Agriculture guzzles far more fresh water than all homes, industries, swimming pools and golf courses combined.
Due to inefficient irrigation, like the jumbo center-pivot systems that douse indiscriminately in circular patterns and pump heavily from underground aquifers, agriculture is often the biggest waster of water as well. For many water activists, Exhibit A is the eight-state Ogallala aquifer that irrigates Nebraska, Kansas, Oklahoma and much of the nation's breadbasket. The Ogallala has been falling faster than it recharges for decades.
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 approaching $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 applications, 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 over-pumped 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. Over that same span, water demand has tripled as farmers intensify their 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, 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.