Rio San Antonio (Colorado–New Mexico)

Rio San Antonio is a tributary of the Conejos River in northern New Mexico and southern Colorado. Via the Conejos River, it is part of the upper Rio Grande system. The river is used extensively for irrigation in its lower course through the southern San Luis Valley.

Rio San Antonio
At Highway 142 east of Manassa
Location
Country	United States
States	Colorado, New Mexico
Physical characteristics
Source	Tusas Mountains
⁃ location	Carson National Forest, New Mexico
⁃ coordinates	36°50′56″N 106°18′15″W[1]
Mouth	Conejos River
⁃ location	near Manassa, Colorado
⁃ coordinates	37°11′14″N 105°53′54″W[1]
Basin size	348 sq mi (900 km2)[2]
Discharge
⁃ location	near mouth[2]
⁃ average	80.6 cu ft/s (2.28 m3/s)
⁃ minimum	0 cu ft/s (0 m3/s)
⁃ maximum	2,620 cu ft/s (74 m3/s)

The river begins at the western boundary of the Carson National Forest, in the Tusas Mountains, in Rio Arriba County, New Mexico.[3] It flows east through a steep canyon and receives Rio Nutritas from the south, continuing east towards San Antonio Mountain.[4] Before reaching the mountain it turns north, entering the rocky Taos Plateau volcanic field on the fringe of the San Luis Valley.[5] It enters Conejos County, Colorado at Ortiz, where the Rio de los Pinos joins from the west.[6] The river turns sharply east at Antonito, then continues northeast through farmland before emptying into the Conejos River at Sego Springs Wildlife Area, a few miles east of Manassa.[7][8]