THE SAN JUAN RIVER STEVEN CHISCHIIIY
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The San Juan River
Steven ChischiII y
Introduction:
The headwaters of the San Juan River of the water is claimed or otherwise has been
begin on the western slope of the Rocky promised to various peoples along the river.
Mountains in southwestern Colorado. The With the placing of the Colorado squawfish
headwaters, located at over 14,000 feet in ele and the razorback sucker on the federal en
vation, are the beginning of what down dangered species list a portion of the water, as
stream is to become the second largest tribu yet undetermined, must be utilized to insure
tary to the Colorado River (San Juan River their survival via preservation of their habitat.
Basin Recovery Implementation Program,
1992). The San Juan River is located within Endangered Species:
the San Juan River Basin (Fig. 1) which drains
approximately 38,000 square miles of south The Colorado squawfish was considered
western Colorado, northwestern New Mexi endangered in 1967 and with the passing of
co, southeastern Utah, and northeastern Ari the Endangered Species Act in 1972 both the
zona. Many tributaries add to the San Juan Colorado squawfish and later the razorback
with the largest being the Animas river. The sucker (1981) were placed on the list. The in
San Juan River flows approximately 360 miles clusion of the Colorado squawfish and
from headwaters in Colorado to the Glen the razorback sucker to the endangered spe
Canyon National Recreation Area in Utah. cies list and the proposal by the United States
There are approximately 7 diversions along Fish and Wildlife Service (USFWS) to
the river concentrated between Navajo reser designate segments of the San Juan River as
voir and Shiprock, NM. These diversions are critical habitat for the Colorado squawfish,
used for irrigation, municipal purposes, and razorback sucker, bonytail chub (Gila
for the generation of power. Weirs construct elegans), and the humpback chub (Gila
ed for diversion purposes are believed to pre cypha) raises further questions as to how
vent the upstream movement of native fish much water can be diverted or otherwise
species. HistOrically, the Colorado squawfish used without negatively affecting these spe
and the razorback sucker were found much cies (Federal Register, 1993). Historically, the
further upriver prior to the construction of bonytail chub was found in the San Juan
the weirs and Navajo dam (NIIP Consulta River; however, they have been extirpated
tion, 1992, SJRBRIP, 1992).
Navajo Reservoir:
Steven Chischilly is a Biologist
Navajo Reservoir built in 1%2 by the Bu and Conservation Educator with
reau of Reclamation stores approximately the Navajo Natural Heritage
1,036,000 acre feet of water (SJRBRIP, 1992; Program, Window Rock, Arizona.
Gallup-Navajo Ind., 1984). A portion of this He is in charge of stewardship
water, along with water attained via other and conservation for the Natural
tributaries, is allotted to many different Heritage Program. His BS degree
parties. Water being an extremely valuable is in Biology from Northern
resource in this part of the country there are Arizona University and he has
many interests with an opinion as to the best nearly completed his MS degree
utilization of this resource. However, much in Biology from the University of
Colorado.
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SAN JUAN BASIN BOUNDARY
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l.ocation Map
Source: SJRBRIP ,1
1992and are currently found in Lake
Mohave in southwestern Arizona Figure 2.
(Jordan 1891; Sigler 1963; Sublette
1977). This population of bony tail Non-native and native fish species
chub found within Lake Mohave of the San Juan River Basin:
is old and may not be reproduc
ing. This may be the reason for Non-Native Fish Species: Native Fish Species:
the very low observed recruit
ment. The humpback chub is also Cutthroat Trout Roundtail Chub
believed to have inhabited the San Rainbow Trout Bony tail Chub
Juan. However, there is no sub Brown Trout Colorado Squawfish
stantial evidence other than par Kokanee Salmon Speckled Dace
tial skeletal remains of what ar Northern Pike Flannelmouth Sucker
chaeologists believe to be either a Red Shiner Bluehead Sucker
bonytail chub or humpback chub Sand Shiner Razorback Sucker
in an archaeological site along the Fathead Minnow Mottled Sculpin
San Juan River. (NIIP Consulta White Sucker Colorado River
tion 1992; SJRBRIP 1992). Black Bullhead Cutthroat Trout
Channel Catfish
The once periodically flooding Plains Killifish
Sanjuan River was dammed and Mosquitofish
its flow controlled with the build Striped Bass
ing of Navajo Reservoir in 1962. Green Sunfish
The environmental consequences Bluegill
entailed in post dam construction Smallmouth Bass
include the decrease of mean river Largemouth Bass
temperature below the dam to the White Crappie
Animas river confluence, the Black Crappie
mem decrease in volume (cfs), the Threadfin Shad
halting of great flood stages
(80,000 cfs), and riverbed geomor Source: SJRBRIP, 1992
phology alteration (Fisheries Sur
vey ofthe Sanjuan River 1987).
With the decrease in mean flood stages there tion, and river alteration is believed to have
was also a correlated decrease in native fish caused native fish populations to decline
species. Native fish species had adapted, (SJRBRIP 1992).
over thousands of years, to the high sediment
load, and the fluctuating flow of the San Juan. Controlling the river to best suit human
Major habitat alterations and the introduction needs caused other problems as well. Exotic
of non-native fish species drastically affected invader plant species like tamarisk or salt
the abundance and distribution of native spe cedar (Tamarix ramosissima) and Russian
cies (Behnke 1980). (Figure 2) olive (Elaeagnus angustifoJia) became estab
lished. Without the frequent flooding of
River Alterations the San Juan River the banks were no longer
scoured and thus cottonwood were soon re
Radical riverine alterations, such as the placed with Russian olive and tamarisk. The
construction of dams, caused dramatic chang encroachment of these species along the
es in the river with regards to associated spe banks of the river channelized the river fur
cies. Detrimental influences upon native spe ther. Generally cottonwood require
cies through the introduction, either acciden flooding events to become established. Tama
tally or intentionally, of apprOximately 23 risk is a phreatophyte; and Russian olive is
non-native fish species. These fish species tolerant of saline soils. Both grow very
largely adapted to warmer water temperature
increased in population. Competition, preda
325rapidly. These species have replaced cotton health of resident fish species. Development
woods in many areas along the San Juan and exploration for gas and oil must and
River. should be done in a way as to minimize detri
mental effects on the river and associated in
Contamination habitants.
Riparian areas along the San Juan River Research
which were regularly inundated with water
during flood periods are no longer inundated. A seven year biological study initiated in
Declines in flood periods have caused concen 1991, as mandated by the USFWS concerning
tration of contaminants in irrigation settling the Animas La-Plata Project (AL.P.), will
ponds which ultimately flow back, either investigate the diversion of water from the
through subsurface or surface flows, into the Animas river into the Ridges Basin Reservoir
San Juan River. Evaporation from these irri and the subsequent effects on the endangered
gation ponds as well as decreased scouring of fish species found down river. This addition
these riparian areas via flooding induce con al diversion from the Animas River is pro
taminant concentration and thus poor habitat posed to be offset by an increased flow release
for fish and waterfowl. The naturally, highly from Navajo Reservoir. The diversion and
seleniferous San Juan Basin exacerbates the storage of water within the Ridges Basin res
situation. Selenium found within these irriga ervoir will identify water resources for south
tion settling ponds concentrate to levels that western Colorado farmers, the Southern Ute
may be dangerous to wildlife. Selenium, at Tribe, Ute Mountain Ute Tribe, and other mu
high levels, has been found to affect repro nicipal and industrial purposes (SJRBRIP,
duction and cause birth defects. It should be 1992).
noted that the concentrations within the irri
gation run-off ponds are high and pose a po Conclusion
tential threat to wildlife. However, when the
water from these ponds enters into the San The San Juan River is a beautiful river pro
Juan River these contaminants are diluted viding water for diverse needs to the people,
and the levels of these elements within the communities, and wildlife existing
river are relatively low (Blanchard, P. Pers. along it's banks. The water is utilized by hu
comm.). mans for irrigation, municipal purposes,
Oil and gas exploration and development power generation, and recreation; however, it
within the San Juan River basin, including should not be forgotten that there are inhabit
drilling in riparian areas, also affect the ants within the river who make the river their
river. Carcinogenic polycyclic aromatic hy home and they have been there longer than
drocarbons (PAH's) bioaccumulate within the human settlements. Parties interested in ob
fatty tissues of fishes and other aquatic taining water from the San Juan River must
fauna. The PAHs are a major contributor to work with the river to provide habitat for the
the pollution found in the San Juan. Oil ex flora and fauna which make up the riparian
ploration and development occurs most of the ecosystem. River straightening, damming,
length of the river from below Navajo Reser further allocations of water, and attempting
voir, NM to Mexican Hat, Utah. Externalle further control of the river may result in fur
sions linked to PAH's have been found on ther destruction of this ecosystem and per
channel catfish and the flannelmouth sucker haps the extinction of the endangered fish
in irrigation drainage study sites. Of the species.
channel catfish sampled 37% had lesions and
of the flannelmouth suckers sampled 50% had
lesions. Also,77% of flannelmouth suckers
sampled from the San Juan River were diag
nosed to have eosinophilic foci (NIIP Consul
tation, 1992). The health of the river and asso
ciated ecosystem can be gauged from the
326References
Behnke, R.J., and Benson, D.E. 1980. Endan Sublette, J.E. 1977. A survey of the fishes of
gered and Threatened Fishes of the Upper the San Juan River basin with particular ref
Colorado River Basin. Cooperative erence to the endangered species. Prepared
Extension Service, Colorado State University, for the United States Fish and Wildlife Ser
Fort Collins, Colorado. Bulletin S03A. 38pp. vice, Albuquerque, New Mexico. 45pp.
Frentzel, Martin. 1991. Squawfish Protected in U.S. Bureau of Reclamation. 1984. Gallup-Na
the Southwest.. Killed for $3 Bounty in the vajo Indian Water Supply Project. U.S. De
Rivers of the Northwest. Albuquerque partment of Interior. Bureau of Reclamation,
Journal. pg.3, sec.C 7/11/91. Washington D.C.
Jordan, 0.5. 1891. Report of explorations in U.S. Department of the Interior. 1993. Fish
Colorado and Utah during the summer of and Wildlife Service. 50 CFR Part 17 Federal
1889, with an account of the fish found in Register 58:6578-6597.
each of the river basins examined. Bulletin,
U.S. Fish Commission. 89:1-40. U.S. Department of the Interior. 1992. NIIP
Section 7 Consultation. Fish and Wildlife
Sigler, W.F., and Miller, R.R. 1963.' Fishes of Service. Albuquerque, New Mexico.
Utah. Utah State Department of Fish and
Game, Salt Lake City, Utah. 203pp. U.S. Department of the Interior. 1992. San
Juan River Basin Recovery Implementation
Program. Fish and Wildlife Service.
Albuquerque, New Mexico. 44pp.
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