It takes roughly 20 gallons of water to make a pint of beer, as much as 132 gallons of water to make a 2-liter bottle of soda, and about 500 gallons, including water used to grow, dye and process the cotton, to make a pair of Levi's stonewashed jeans.

Though much of that water is replenished through natural cycles, a handful of companies have started tracking such "water footprints" as a growing threat of fresh-water shortages looms. Some are measuring not just the water used to make beverages and cool factories,...