In California’s Central Valley, 100 miles east of San Francisco, the San Joaquin and Tuolumne rivers meet. Their waters mingle amid a wide flat plain of shrubs, cottonwood and oak trees. The Dos Rios Ranch Preserve, 1,600 acres of wetlands, river habitat and rolling hills, sits at the site of this juncture. On clear days, the Sierra Nevada rises in the east and the Coast Range to the west.