LA Times: John Wesley Powell, whose legendary descent of the Colorado River in 1869 brought the one-armed explorer fame and celebrity, worried about America's westward migration. The defining characteristic of Western lands was their aridity, he wrote, and settlement of the West would have to respect the limits aridity imposed. He was half right. The subsequent story of the West can indeed be read as an unending duel between society's thirst and the dryness of the land, but in downtown Phoenix, Las Vegas...