The amount of water on Earth hasn’t changed appreciably since Caesar and Cleopatra took a little cruise on the Nile. But the hydrologic cycle has changed where that water goes – and we are heading up a very dry creek. California has always teetered on the edge of drought, but hereafter, how we eat, drink, and even survive depends more than ever on the ingenuity of science and human willingness to suck it up by not sucking down so much water.