9521

• UCREFRP Catalog Number: 9521
• Author: Liebermann, T. D., D. K. Mueller, J. E. Kircher and A. F. Choquette.
• Title: Characteristics and Trends of Streamflow and Dissolved Solids in the Upper Colorado River Basin, Arizona, Colorado, New Mexico, Utah, and Wyoming.
• USFW Year: 1989.
• USFW - Doc Type: Denver.
• Copyright Material: NO

confluence and Lee Ferry, Ariz. (pl. 1). These regions are
called the Grand, Green, and San Juan regions.
This section contains a summary and analysis of the
historical streamflow and water-quality records at the 70
selected sites. The analysis includes determination of annual
and monthly means and results of trend analyses. Predomi-
nant cations and anions are reported, based on fraction of
the dissolved-solids load. Bicarbonate is considered the
primary form of dissolved carbon in the carbonate-equivalent
fraction. Sodium is considered the primary component of the
sodium-plus-potassium fraction.
Significant differences between the preintervention and
postintervention periods at sites downstream from major
interventions are reported as the step trends in the median
values. The percentage change from the preintervention
median also is reported. Monotonic trends are reported as
the annual rate of change of the median value during the
period of analysis. An estimate of the percentage change in
median from the beginning to the end of the period also is
reported. This change is computed using the ratio of the total
change during the period over the estimated median at the
beginning of the period:
Am = 100 n + T I (5)
M-T(n + 1)l2
where
Am = the change in median, in percent;
n = the number of years;
T =the monotonic trend per year; and
M= the median for the entire period.
The denominator [M - T(n + 1)l2] estimates the median
value for the beginning of the period. The median dissolved-
solids concentration was used for evaluating the percentage
change in flow-adjusted concentration. For sites having
records divided into preintervention and postintervention
periods, the monotonic trends for each period are presented.
Trends are not reported if the period of record for a site is
less than 10 years.
The period of record for the 70 sites ranges from 3 to
55 years. Therefore, results commonly cannot be compared
between sites because of differences in the period of record.
Streamflow hydrograph analyses were based on the entire
period of record for streamflow and not confined to the
period of concurrent water-quality record. For this reason
streamflow analyses may have a different period of record
than the dissolved-solids analyses throughout the report.
Grand Region
Most of the streamflow of the Colorado River in the
Grand region originates on the western slope of the Rocky
Mountains in Colorado. Areas in Utah contribute only minor
quantities to the total streamflow from this region. The
drainage area in the Grand region is about 27,000 mil. The
Grand region comprises 24 percent of the total drainage area
in the Upper Colorado River Basin; it contributes 47 per-
cent of the streamflow and 51 percent of the total dissolved-
solids load that leaves the Upper Colorado River Basin at
Lee Ferry, Ariz. The major tributaries in the Grand region
are the Eagle, Roaring Fork, Gunnison, and Dolores Rivers.
Data from 21 sites were evaluated for the Grand
region (pl. 1). Long-term mean annual runoff, streamflow,
dissolved-solids concentration and load, and major-
constituent load were determined at each of these sites
(table 5). Collins diagrams of chemical composition at several
sites are shown in figure 7. The carbonate plus bicarbonate
concentration in these diagrams was computed from the
carbonate equivalent of alkalinity, and assuming that bicar-
bonate is the dominant species. Significant annual monotonic
trends in the data for sites in the Grand region are reported
in table 6. For purposes of discussion, the Grand region was
divided into three subregions: the upper Colorado, the Gun-
nison, and the lower Colorado (pl. 1).
Upper Colorado Subregion
The upper Colorado subregion includes the drainage
area of the Blue, Eagle, Roaring Fork, and Fraser Rivers
and tributaries, and Plateau, Roan, Parachute, and Rifle
Creeks. The upper Colorado subregion also includes the
main-stem Colorado River from its headwaters in the moun-
tains to the confluence with the Gunnison River.
Numerous reservoirs and diversions affect the stream-
flow in this subregion. The Alva B. Adams Tunnel/Lake
Granby diversion and storage system is the largest transbasin
export in the entire Upper Colorado River Basin. The Alva
B. Adams Tunnel and Shadow Mountain Reservoir were
completed in 1947, but major diversions did not begin until
the completion of Lake Granby in 1950. Lake Granby stores
water from the main stem of the Colorado River during the
snowmelt season. Water then is pumped into Shadow Moun-
tain Reservoir, which is continuous with Grand Lake. Diver-
sions from Grand Lake via the Alva B. Adams Tunnel to
the South Platte River basin are large during all months,
except June, and average about 250,000 acre-ft/yr (table 1).
Homestake Tunnel and Reservoir have diverted water
from the Eagle River basin since 1967. The Moffat Water
Tunnel has diverted water from the Fraser River basin since
1936. The H.D. Roberts Tunnel, operating in conjunction
with Dillon Reservoir, has diverted water from the Blue
River basin since 1963. The Twin Lakes Tunnel (1935) and
the C.H. Boustead Tunnel (1972) divert water from the Roar-
ing Fork River basin. Ruedi Reservoir (1968) provides
regulation of streamflow downstream from the diversions to
the C.H. Boustead Tunnel.
20 Characteristics and Trends of Streamflow and Dissolved Solids in the Colorado River Basin