San Juan River

Where the San Juan River comes from

About 380 miles from the San Juan Mountains of Colorado, through New Mexico and the Four Corners, to Lake Powell.

Map of the San Juan River — San Juan River. River lines from the USGS National Hydrography Dataset.

Headwaters

The Animas River canyon above Durango, by William Henry Jackson, about 1900.W. H. Jackson. The Metropolitan Museum of Art, public domain · source

Two forks below the Continental Divide

The San Juan begins high in the San Juan Mountains of southwestern Colorado. Its East and West Forks drain the slopes near Wolf Creek Pass and join north of Pagosa Springs. Snowmelt from these mountains is most of the river's water.¹

Navajo Lake

Just across the New Mexico line the river is held back by Navajo Dam, finished in 1962. The Piedra and Los Pinos rivers and the Navajo River reach the river in or above the reservoir, so their floods are held there too.^2,1

The Animas

Below the dam the biggest addition is the Animas River, which rises around Silverton in the San Juan Mountains and joins at Farmington. It is not dammed, so its spring snowmelt and fall storm floods reach the San Juan in full.³

The river, top to bottom

San Juan MountainsEast and West Forks join above Pagosa Springs.
Navajo LakePiedra, Los Pinos and Navajo rivers; Navajo Dam controls releases.
FarmingtonThe Animas and La Plata join.
Four CornersThe Mancos comes in from Mesa Verde country.
Aneth & Montezuma CreekMcElmo and Montezuma creeks join from the north.
BluffRecapture Creek joins; Chinle Creek comes in from Arizona below town.
Mexican Hat & the GoosenecksThe river winds through deep entrenched meanders.
San Juan arm, Lake PowellThe river ends in the lake, in Glen Canyon.

Main tributaries

Ancient ruins at the head of McElmo Creek, Hayden Survey, 1870s.W. H. Jackson, Hayden Survey. U.S. National Archives, public domain · source

Stream	Joins	Notes
Animas River	Farmington, NM	From Silverton; the largest tributary and the one most likely to flood.
Navajo, Piedra, Los Pinos	Navajo Lake	Mountain rivers mostly held by the reservoir.
La Plata River	Farmington, NM	From the La Plata Mountains.
Mancos River	Near Four Corners	Drains Mesa Verde; can run hard in summer storms.
McElmo & Montezuma creeks	Near Aneth, UT	Desert creeks that flash after storms.
Chinle Creek	Below Bluff, UT	Drains a large part of the Navajo Nation in Arizona.

Why it matters for floods

Spring snowmelt brings the San Juan its long high water, mostly from the Animas now that Navajo Dam holds the upper river. Its biggest floods came in fall, when tropical moisture stalled over the mountains. Summer storms over the desert creeks below Farmington send fast, muddy surges toward Bluff and Mexican Hat.^4,1 The live map watches the gauges along the way.

The San Juan River and its Tributaries

Sources

Southwest River Watch · History · Terms