WSP12063

• File Number: 8240.300.31.J
• Description: San Juan River - Environmental Studies
• Basin: San Juan/Dolores
• Water Division: 7
• Date: 2/1/2000
• Title: Non-Native Species Interactions: Management Implications to Aid in Recovery of the Colorado Pikeminnow and Razorback Sucker in the San Juan River
• Water Supply Pro - Doc Type: Report/Study

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The San Juan River Recovery Implementation Program (SJRlP) was established as a response to
information needs regarding endangered fish species and proposed development of water
resources. Since 199 I, the SJRIP has orchestrated the conduct of research to address a variety of
questions regarding native fish species recovery and management and water development The
focus of this portion of research funded through the SillP is to characterize the interactions
between native and non-native fishes under a variety of habitat (flow) conditions. Identifying the
mechanisms of interspecific interactions that negatively impact native fishes will allow for the
development of management options designed to protect and restore the native fish conununity,
The primary goal of this research is to evaluate and characterize the response of non-native fishes
to flowfhabitat manipulations designed to benefit the native fish community with emphasis on
endangered Colorado pikeminnow Ptychocheilus lucius and razorback sucker Xyrauchen
texanus.

STUDY AREA DESCRIPTION

The Colorado River Basin drains 632,000 km2 in the western United States and northwestern
Mexico (Carlson and Muth 1989) and, for the purposes of water management, is split into upper
and lower basins at Lee's Ferry, Arizona (1922 Colorado River Compact). Several large sub-
basins are identified within the upper (Green, Colorado, Gunnison, San Juan) and lower (Little
Colorado, Virgin, Gila) basins (Figure}). From the headwaters to its confluence with the Gulf of
California, Mexico, the Colorado River flows for a distance of 2320 km, and ranges in elevation
from more than 4000 m in headwater reaches to sea level at the terminus. Carlson and Muth
(1989) summarized the geologic history and human occupation of the Colorado River Basin,

The San Juan River is a major tributary of the Colorado River and drains 99,200 km2 in
Colorado, Utah, Arizona, and New Mexico (Figure 2). From its origins in the San Juan
Mountains of southwestern Colorado at elevations exceeding 4,250 m, the river flows westward
for about 570 Ian to the Colorado River. The major perennial tributaries to the San Juan River
are the Navajo, Piedra, Los Pinos, Animas, La Plata, and Mancos rivers, and McElmo Creek. In
addition there are numerous ephemeral arroyos and washes contributing little total flow but large
sediment loads,

Navajo Reservoir, completed in 1963, impounds the San Juan River, isolating the upper 124 km
of river and partially regulating downstream flows. The completion of Glen Canyon Dam and
subsequent filling of Lake Powell in the early 1980's inundated the lower 87 Ian of the river,
leaving about 359 km ofriver between the two bounding features.

From Navajo Dam to Lake Powell, the mean gradient of the San Juan River is },67 mfkm.
Locally, the gradient can be as high as 3.5 mlkm, but taken in 30 km increments, the range is
from

San Juan R',ver Non-native Species Interactions, Final Repon, I February 2000

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