Azotea Tunnel West Portal, Colorado

The Oso Diversion Dam is two and a half miles west of the Continental Divide, and two and a half miles north of the New Mexico state line. It is the origin of the Azotea Tunnel, which takes water from the western slope in Colorado, and delivers it to the eastern slope in New Mexico. The Oso Dam is the collection point for 15 miles of tunnels which collect water from streams on the western side of the Divide and bring it to Oso. It is part of the U.S. Bureau of Reclamation’s San Juan-Chama Project, moving water from the San Juan River to the Chama River, to help with irrigation in northern New Mexico, but also to supply more water to New Mexican cities and towns, primarily Albuquerque and Santa Fe. Constructed in 1970, the Azotea Tunnel originates at the diversion dam and runs south, underground, for more than 12 miles, crossing under the Divide in New Mexico, before discharging water previously destined for the Colorado River, into the Rio Grande’s watershed. It is the only trans-state, trans-divide tunnel along the Divide.