The San Juan River

◉ The San Juan River is a major tributary of the Colorado River in the southwestern United States, providing the primary drainage for the Four Corners region of Colorado, New Mexico, Utah, and Arizona. Originating from snowmelt in the San Juan Mountains (part of the Rocky Mountains) of Colorado, it flows 383 miles (616 km) through the deserts of northern New Mexico and southeastern Utah to join the Colorado River at Glen Canyon.
◉The San Juan River provides habitat for at least eight native fish species – cutthroat trout, roundtail chub, speckled dace, flannelmouth sucker, bluehead sucker, mottled sculpin, Colorado pikeminnow, and razorback sucker, with a possible ninth, bonytail chub. The last three are considered endangered under the Endangered Species Act of 1973, and are rarely, if ever, found in the San Juan River today. With the exception of trout and dace, which inhabit clear, cool mountain streams in the headwaters, native fish are mostly adapted to the warm, shallow, silty characteristics of the lower San Juan. The San Juan cutthroat trout, a unique lineage of cutthroat trout endemic to the river and its tributaries, was thought to be extinct until its rediscovery in 2018. Additionally, approximately 23 species of non-native fish have been introduced to the San Juan River watershed. Common carp and channel catfish have spread into the lower reaches of the San Juan River. In the "tailwater" stretch below Navajo Dam, introduced rainbow trout and brown trout thrive in the cool, stable flows released by the dam. Rainbow trout and brown trout have also proliferated in the headwaters of the San Juan River above Navajo Lake.