That’s the conclusion from a new study in the journal Water Policy, whose authors compared the water supply histories of four cities — San Diego, Phoenix, San Antonio, and Adelaide, Australia. Among the lessons learned? Urban water conservation, recycling, and desalination aren’t silver bullets. In fact, the best solution may lie upstream with farmers — saving just 5-10 percent of agricultural irrigation in upstream watersheds could satisfy a city’s entire water needs. But the time to act is now, argues Brian Richter, a senior freshwater scientist at The Nature Conservancy and the study’s lead author — he says a global urban water crisis is already here. Below, Richter tells us more about what cities need to do to say on the right side of dry. Q. Many cities take a similar pattern of water development, according to your research – going from exhausting local surface and groundwater supplies to importing water to implementing water conservation to finally recycling water or desalination. Why is this pattern unsustainable? Q. Are we looking at a crisis in securing urban water supplies in the near future, either for U.S. cities or globally?