The Rio Chama originates in south-central Colorado, just above the New Mexico border in the San Juan Mountains and Rio Grande National Forest. The main stem Rio Chama begins at the confluence of two short headwater tributaries called West Fork and East Fork. The West Fork flows eastward from the Continental Divide. Across the divide lies the Navajo River, one of the headwater tributaries of the Colorado River. The East Fork extends a few miles into Conejos County, Colorado to a source near one of the headwater tributaries of the Conejos River. The confluence of the forks lies just within Archuleta County, Colorado. From there the Rio Chama flows generally south. After a few miles the river enters Rio Arriba County, New Mexico, and flows by the town of Chama. The tributary Willow Creek joins the Rio Chama after being impounded as Heron Lake by Heron Dam. Willow Creek flows from the dam about to the Rio Chama. A couple miles below that the Rio Chama flows into El Vado Lake, a reservoir created by El Vado Dam.