he next time you stop off at a pub for a quick bite, think about this: It took around 630 gallons of water to make your burger. Your pint of beer used around 20 gallons. Manufacturing your blue jeans and T-shirt drank up about 1,218 gallons of water: 505 and 713 gallons, respectively. Total: Nearly 1,900 gallons of water—and that’s without fries on the side. These quantities are the “water footprint” of each product: the total amount of freshwater used in its manufacture, including producing the ingredients. For many products, that footprint is Paul Bunyan–sized: With water seemingly cheap and plentiful, there has been little incentive to try to keep it small. But today, that’s changing. Even though much of the water we use for growing food and making products is replenished by natural hydrological cycles, freshwater will be less reliable and available in the coming century. Population growth is increasing both demand for water and pollution of potable supplies. At the same time, climate change is disrupting historical precipitation patterns, shrinking freshwater sources such as glaciers and snowpack, and creating unprecedented droughts and floods. According to an analysis published in Nature in September 2010, the freshwater supplies of most of the world’s population are at high risk.