CIENTISTS NOW SAY that the last two decades of drought in the West are the worst in 1200 years. In my home near the San Francisco Bay, I can dismiss this notion when water still flows from my taps. But even in the city, paved and landscaped, tamed and mastered, small signs of the drought appear in places where the natural world pushes through. The creek near my house, its flow directed through concrete culverts to avoid any