For most of the two hundred thousand years or so of human existence, we used but a small fraction of the earth’s freshwater resources. It has been only a few thousand years since humans first learned to exert any control over water by channeling it for irrigation and supply for cities. In a geological heartbeat, however, we have reached the point where we now use half of the world’s freshwater for our own consumption, leaving minimal amounts for ecosystem functioning. Agriculture uses the most water—about 70 percent globally—with population growth, shifts to higher meat consumption, and the use of grain in biofuels driving increased demand.1 It is fairly common in some areas to use 70 percent of annual flows and, in a few cases, to use as much as 120 percent or more by drawing on fossil groundwater. By extracting groundwater, reducing lakes and rivers beyond the rate of replenishment, and polluting the freshwater that we do have, we are quickly depleting our available supplies.