[2] From there, it flows generally southwest, receiving the waters of its tributary Comanche Creek at the north end of Valle Vidal.

The creek then travels generally northwestward, following alongside State Road 196 through the small town of Amalia.

It leaves the mountains after passing through a diversion dam — the beginning of the Acequia Madre irrigation ditch — and just before flowing through the town of Costilla, entering the broad, flat plain of the Taos Plateau volcanic field.

Soon after crossing the border, the creek turns to the southwest and empties into the Rio Grande, its mouth in a gorge just to the northwest of Ute Mountain.

[4] The New Mexico Department of Game and Fish implemented the final phase of the Restoration of Rio Grande Cutthroat Trout (Oncorhynchus clarki virginalis) and the Native Fish Community to the Upper Rio Costilla Watershed project in March 2021, which should be complete by the fall of 2021.