WSP07867

• File Number: 8240.300.31.J
• Description: San Juan River - Environmental Studies
• Basin: San Juan/Dolores
• Water Division: 7
• Date: 2/1/2000
• Title: Ichthyofaunal Surveys of Tributaries of the San Juan River - NM
• Water Supply Pro - Doc Type: Report/Study

C)
C:1
l'''
r .~
.;;..
o

The distribution of native and non-native species can be observed in the data provided by
historical sampling, Earliest sampling efforts resulted in the capture of mostly native
fish, while more recent sampling efforts have produced an increasing number of non-
native species. Distribution and composition of native and non-native fish in tributaries
of the San Juan River is dependent on numerous physical and biological variables, A
comparison of historical fish surveys provides valuable insight into temporal changes in
fish populations and composition in tributaries of the San Juan River,

I

I
1

Table 1, Number of collections by decade made in ttibutaries of the San Juan River.

1934 - 1949 1950 - 1969 1970 - 1979 1980 - 1989 1990 - 1999
2 2 24 19 110
Animas
Florida 2 9 21
La Plata 1 24 ~ 80
"-
Mancos 13 10 29
Mc Elmo 10 7 4
Piedra 2 7 6
Los Pinos 8 ] 6
Na~'ajo 9 7
San Juan 3 18

I

I

I
,I

Study Area

The San Juan River is a major tributary of the Colorado River and drains 99,200 km" in
Colorado, Utah, Arizona, and New Mexico. From its origins in the San Juan Mountains
of southwestern Colorado at elevations exceeding 4,250 m, the river flows westward for
about 570 kIn 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 (Figure I), 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 kIn of river and partially regulating downstream flows. The completion of Glenn
Canyon Dam and subsequent filling of Lake Powell in the early 1980's inundated the
lower 87 kIn of the river, leaving about 359 kIn of river between the two bounding
features.

This study area included all major tributaries of the San Juan River that originate in
Colorado, The downstream boundary of tributaries within the study area was their point
of confluence with the San Juan River. The results of some surveys conducted on the
San Juan River upstream of Navajo Reservoir have also been provided, Tributaries of the
San Juan River that were represented in these results include; the Animas, Florida, La

Draft Final Tributary Report
Miller Ecological Consultants, Inc.

January 31, 2000
Page 2