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

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OCT NOV DEC JAN FEB MAR APR MAY JUNE JULY AUG SEPT
Figure 10. Mean daily streamflow at selected sites in Gunnison subregion of Grand region. A, Site 12,
Uncompahgre River at Delta, Colo. B, Site 13, Gunnison River near Grand Junction, Colo.
was identified (table 4). This decrease is 8 percent of the
preintervention median. It corresponds in magnitude with
the decrease in the load at site 12 on the Uncompahgre River,
which is tributary to the Gunnison River upstream from site
13. Monthly step-trend decreases in dissolved-solids concen-
tration of about 600 mg/L occurred during the low-flow
season of August through March; corresponding increases
in streamflow also occurred (fig. 11). Streamflow and
dissolved-solids load decreased during the snowmelt period
of May and June, and dissolved-solids concentration in-
creased slightly during May.
Annual monotonic-trend analysis for the preinterven-
tion period indicated a significant decrease in median annual
flow-adjusted concentration of 2.8 mg/L per year, a
13-percent decrease in the median during the 32-year period.
During the postintervention period, annual monotonic-trend
analyses indicated a significant decrease in median annual
dissolved-solids concentration of 16.1 mg/L per year and a
highly significant decrease in median annual flow-adjusted
concentration of 9.9 mg/L per year. These trends represent
a 39-percent decrease in median annual concentration and
a 26-percent decrease in median annual flow-adjusted
concentration during the 18-year period. The postinterven-
tion trends may be related to the completion of Morrow Point
and Crystal Reservoirs downstream from Blue Mesa
Reservoir.
Lower Colorado Subregion
The lower Colorado subregion includes the drainage
areas of the Dolores River and its tributaries and the Colo-
rado River between Grand Junction, Colo., and the con-
fluence with the Green River. About 70,000 acres is irrigated
along the Colorado River in the Grand Valley near Grand
Junction. Irrigation water for about 32,000 acres is supplied
by the Grand Valley Canal (constructed before 1900) and
Redlands Power Canal. The remaining area is supplied by
the Government Highline Canal built by the Federal Grand
Valley Project in 1917. This canal takes water diverted from
a dam across the Colorado River upstream from Grand Junc-
tion and transports it to cropland parallel to the river for 55
mi. Total irrigation diversions averaged 400,000 acre-ft/yr
by the early 1930's. Consumptive use by irrigation has been
estimated at 247,000 acre-ft/yr (U.S. Bureau of Reclama-
tion, 1985a). Most of the irrigated land in the Grand Valley
is underlain by Cretaceous Mancos Shale, which is a source
of mineral salts dissolved in irrigation-return flow. The U.S.
Bureau of Reclamation (1985a) estimated that 580,000 tons
of dissolved solids per year is added to the Colorado River
in the Grand Junction area. As part of the Colorado River
Basin Salinity Control Program, the lining of canals and
laterals has been started. The completed project will decrease
the dissolved-solids input by an estimated 140,000 tons/yr.
Stage I of the project, affecting about 10 percent of the
irrigated area, was completed in April 1983.
Approximately 28,000 acres is irrigated within the San
Miguel River basin and about 7,000 acres in the remainder
of the Dolores River basin. About 116,000 acre-ft of water
is exported annually from the Dolores River to Montezuma
Valley in the San Juan River basin for irrigation of 37,000
acres (U.S. Forest Service and others, 1976). The Dolores
Project, under construction since 1977, will export an addi-
tional 81,000 acre-ft/yr of water to the San Juan River basin.
The Dolores River channel crosses Paradox Valley, one
of a series of collapsed salt anticlines in the Paradox Basin.
The river flows directly across the soluble Paradox Member
of the Hermosa Formation, which is composed of about
14,000 ft of halite and halite-rich shale. As specified in Title
H of the Colorado River Basin Salinity Control Act, con-
struction of salinity-control facilities in the Paradox Valley
28 Characteristics and Trends of Streamflow and Dissolved Solids in the Colorado River Basin