Colorado

Trout habitat is found as soon as the Rockies pop out along the western edge of the Great Plains, where the elevation rises above 6,000 feet or so.  Most streams are now inhabited by exotics:  brown trout and rainbows in the valleys, brook trout in the headwaters.  Cutthroat, the native species, can be found in isolated headwaters: Rio Grande Cutthroat in the south; Greenback Cutthroat along the east slope from the Arkansas River drainage to the Wyoming border; and Colorado River Cutthroat west of the Continental Divide.

Native trout populations are reasonably well documented because of Endangered Species Act reporting requirements (and funding). The Greenback population is somewhat problematic, because the documentation is older, and recent genetic testing which suggests that most restored "greenback" populations aren't greenbacks at all, but Colorado River Cutthroat which had survived long-forgotten stocking activity from the late 19th and early 20th century. CDOW is less forthcoming than many state wildlife agencies with GIS information about trout populations, though has helpfully provided information about special regulations, gold medal streams, and recommended fishing spots. The state's water quality program does designate cold water habitat. We've synthesized the available information in the webmap, and in the data available for download via the zip file.