If you follow the Colorado River from the snow-covered Rockies in the upper right corner of this satellite image, you can barely make out its path through Lake Powell, the Grand Canyon, Lake Mead, and then southward to Mexico where it emerges into the Gulf of California under a cloud of dust that appears to be borne by a stiff wind. In the upper left corner of the image, a bank of haze hangs over the eastern side of California's San Joaquin Valley.