San Juan River

San Juan River

From the San Juan Mountains through Farmington and the Navajo Nation to Lake Powell; its largest known flood came from days of fall rain, as October 2026's did.

Map of the San Juan RiverSan Juan MountainsLa Plata MountainsAbajo MountainsSan Juan RiverShiprock 7,177 ftDurangoFarmingtonFour CornersNavajo DamMancos RiverChinle Creek25 miles
San Juan River. River lines from the USGS National Hydrography Dataset.

People and the river

Ancestral Puebloan ruins in the canyon of the Mancos, a San Juan tributary, photographed by William Henry Jackson for the Hayden Survey in the 1870s.
Ancestral Puebloan ruins in the canyon of the Mancos, a San Juan tributary, photographed by William Henry Jackson for the Hayden Survey in the 1870s.W. H. Jackson, Hayden Survey. U.S. National Archives, public domain · source
  1. For centuriesAncestral Puebloan towns lined the river and its tributaries; today it runs through Diné (Navajo), Ute Mountain Ute and Southern Ute homelands and forms much of the Navajo Nation's northern edge.1
  2. 1880Hole-in-the-Rock pioneers reached the river and founded Bluff.1
  3. 1962Navajo Dam began storing water above Farmington, taming the main stem's spring floods. The Animas, its biggest tributary, still runs free.2
  4. Aug 5, 2015The Gold King Mine blowout above Silverton sent about 3 million gallons of acidic, metal-laden water down the Animas and the San Juan, through some 200 miles of Navajo land.3,4

Biggest flows

~150,000cfs
San Juan near Bluff, Oct 6, 1911: the largest flood known there, likely in many centuries5
estimated
~54,000cfs
San Juan at Four Corners, Oct 25, 20266
provisional reading
~41,000cfs
San Juan near Bluff, Oct 26, 20266
provisional reading

Measured: a USGS gauge reading. Estimated: reconstructed after the fact from high-water marks or flood deposits. Provisional: USGS readings not yet reviewed.

Floods that mattered

The October 1911 flood at Pagosa Junction, Colorado.
The October 1911 flood at Pagosa Junction, Colorado.Photographer unknown, 1911. Public domain · source

Oct 1911: the Four Corners flood

Days of heavy rain swept away bridges, farms and parts of towns from Pagosa Springs and Durango to Farmington and Bluff.7,5

Oct 2026

A long fall storm on soaked ground sent the San Juan, Animas and their tributaries far over their banks; readings below are provisional.6

The San Juan River and its Tributaries

Map of the San Juan River and its tributaries in southwestern Colorado, northwestern New Mexico and southeastern Utah, with San Juan Mountains, La Plata Mountains, Abajo Mountains: rivers, side canyons, contour lines and summit elevations, in a classic survey style.
A classic map of the river and the mountains around it. Full size · Vector (SVG) · © 2026 Southwest River Watch
Sources
  1. Utah History Encyclopedia: San Juan River
  2. Navajo Dam (Bureau of Reclamation project history, via Wikipedia)
  3. Arizona DEQ: Gold King Mine spill
  4. 5280: How the Gold King Mine spill threatens the Navajo Nation
  5. USGS: Paleoflood hydrology of the San Juan River near Bluff (OFR 01-314)
  6. NOAA National Water Model archive of USGS 15-minute readings (provisional)
  7. KSUT: The 1911 Four Corners flood, could it happen again?

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