hadn’t been living in arid Southern California for long before I toured the Colorado River Aqueduct — the 242-mile system of dams, pumps, and channels that divert water through the Mojave Desert to the sprawling 20-million population Los Angeles region. It’s a vast engineering marvel and something that, in concept, is remarkably simple. The New Deal-era Parker Dam — a magnificent Art Deco structure that straddles the California-Arizona border — traps water from the river and pumps it to a holding pool at the top of a mountain.