7370

• UCREFRP Catalog Number: 7370
• Author: Platania, S. P.
• Title: Biological Summary of the 1987 to 1989 New Mexico-Utah Ichthyofaunal Study of the San Juan River.
• USFW Year: 1990.
• USFW - Doc Type: Albuquerque, New Mexico.
• Copyright Material: NO

the closure of Navajo Reservoir (Archuleta gauge # 09355500,
1,317 cfs [37.3 m3/s], 1954 to 1962; 1,190 cfs [33.7 m3/s], 1963
to 1985), scant amount of pre-impoundment flow data from
Archuleta limit interpretation. In addition to moderating
natural flow extremes, hypolimnetic release of water from Navajo
Reservoir has decreased mean annual water temperature and
diminished temperature fluctuations of the San Juan River,
especially upstream of its confluence with the Animas River (U.S.
Geological Survey 1913 to 1989).
The Animas River, largest tributary by volume of the San
Juan River downstream of Navajo Reservoir, flows south from the
San Juan Mountains in Colorado and is confluent with the San Juan
River at Farmington, New Mexico. Discharge of the Animas River
is largely unregulated by upstream dams so natural spring peaks
and summer/fall low flows are exhibited. Mean annual discharge
of the Animas River at Farmington (1913 to 1985, gauge #
09364500) was 929 cfs (26.3 m3/s) and high and low flows of
25.,000 cfs (708 m3/s) and 1 cfs (0.03 m3/s), respectively, have
been recorded. Discharge of the Animas River can approach that
of the San Juan River during spring runoff; for example, in may
1987, the Animas and San Juan rivers discharged 3,047 cfs (86.3
m3/s) and 3,422 cfs (96.9 m3/s), respectively (U.S. Geological
Survey 1987).
Tributaries downstream of Farmington add no appreciable
amounts of water, except during flood, to the San Juan River.
Flashy runoff and erosion within small tributary streams are
promoted by the region's poor soil development and lack of
vegetation. During periods of flow, Gobernador, Chaco, and Red
washes, Canyon Largo, the Animas River, McElmo, Montezuma,
Desert, and Chinle creeks contribute a heavy silt load to the San
Juan River. overall, the San Juan River below Farmington
exhibits a fairly natural discharge regime (although reduced in
magnitude), having peak flows during spring runoff and low flow
periods in summer and fall.
River Diversions
Prior to the construction of Glen Canyon Dam and filling of
Lake Powell in the early 1960's, the San Juan River joined the
Colorado River in Glen Canyon. Now it flows directly into Lake
Powell approximately 54 river miles (87 km) upstream of their
natural confluence. Thus, with Navajo Reservoir near its head
and Lake Powell at its mouth, the San Juan River in New Mexico
and Utah is a 245 mile (395 km) lotic system bounded by two
reservoirs.
Between Navajo Reservoir and Lake Powell, there are several
points of water diversion from the San Juan River. Downstream
from Farmington, water is diverted for the Farmers Mutual Ditch,
Fruitland Irrigation Canal, Jewett Valley Ditch, Four Corners
Power Plant pumping station, Hogback Canal, Cudei Ditch, and by
other smaller water users. Excess water from the Four Corners
Power Plant is returned to the San Juan River via Chaco Wash.
There are no diversions on the San Juan River in Utah.
10