WSP11103

• File Number: 8240.300.10
• Description: San Juan Recovery Implementation Program
• Basin: San Juan/Dolores
• Date: 2/1/1995
• Author: SJRIP
• Title: San Juan River Basin Recovery Implementation Program - Program Document
• Water Supply Pro - Doc Type: Publication

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10

2.0 BACKGROUND

The San Juan River sub-basin is the second largest of the three
sub-basins which comprise the Upper Colorado River basin (Figure
1). The San Juan River sub-basin drains about 38,000 square
miles of southwestern Colorado, northeastern Arizona,
northwestern New Mexico, and southeastern Utah. From its origins
in the San Juan Mountains of Colorado, the San Juan River flows
some 31 miles to the New Mexico border, 190 miles westward to the
Four Corners area, and thence another 136 miles to Lake Powell.
In its upper reaches, the river traverses rugged terrain and has
a relatively high gradient. The river emerges from canyon-bound
reaches shortly after entering New Mexico and flows through a
broad floodplain for much of its course in New Mexico and Utah.
About 70 miles upstream of Lake Powell, the river again enters
canyon reaches for the remainder of its course. The river is
generally restricted to a single channel in canyon portions, but
is often divided into several channels in floodplain reaches.

The San Juan River has comparatively few perennial tributaries,
most of which are in upper reaches. Historically, Los Pinos,
Piedra, Navajo, Animas, La Plata, and Mancos rivers, Rio Blanco,
and McElmo Creek were the only perennially flowing tributaries.
Other streams such as Montezuma and Chinle creeks seasonally
contributed flows. Numerous washes and arroyos also entered the
river, but none provided regular flow. Among tributaries, the
Animas River contributed the greatest flow.

2.1 FISH FAUNA

2.1.1 Native Fish Fauna

Ichthyofaunal surveys of the San Juan basin prior to extensive
European settlement were very limited. This work, nevertheless,
documented the occurrence of at least eight and possibly nine
native fish species (Table 2.1): cutthroat trout, roundtail
chub, Colorado squawfish, speckled dace, flannelmouth sucker,
bluehead sucker, razorback sucker, and mottled sculpin. Based
upon two specimens and skeletal remains in Native American
middens, bony tail chub may also have inhabited the river. Of
these, Colorado squawfish, razorback sucker, and bony tail chub
are listed as endangered under the authority of the Endangered
Species Act of 1973, as amended. In addition, New Mexico lists
roundtail chub as endangered; Colorado classifies the
flannelmouth sucker, bluehead sucker, and roundtail chub as
species of special concern; and Utah lists the roundtail chub and
Colorado River cutthroat trout as sensitive species.

Although Colorado squawfish was reported in the San Juan Drainage
prior to 1900, the first confirmed records were not until 1936
when three juveniles were captured at Alcove Canyon, Utah.