This species is endemic to the west of the United States. Its range includes the Sierra Nevada, California, north to the Pit River, south to the Tehachapi Mountains, and extends east along major rivers to the Owens Valley and west-central Nevada, at elevations of about 90 to 2,440 m (300 to 8,000 feet) (Rossman et al. 1996, Ernst and Ernst 2003, Stebbins 2003).
This species is represented by a large number of occurrences (subpopulations). The adult population size is unknown but presumably exceeds 10,000. This snake is locally common in various parts of its range. The extent of occurrence, area of occupancy, number of subpopulations, and population size are probably relatively stable or declining at a rate of less than 10% over 10 years or three generations.
Habitats of this highly aquatic snake include pools of permanent or seasonal streams (often rocky), meadow ponds, lakes, reservoirs, and associated riparian zones (e.g., cottonwood, willow, sycamore, alder), in areas with oak woodland, grassy valleys, chaparral, montane coniferous forest, or (east of the Sierra crest) pine-juniper-sagebrush (Rossman et al. 1996, Ernst and Ernst 2003, Stebbins 2003).
Photograph is available under a Creative Commons License from Bob White.