S3_11-15-04

• Basin: Statewide
• Title: SWSI Phase 1 Report - Section 3 Physical Environment of the Major River Basins
• Date: 11/15/2004
• Author: CWCB
• SWSI - Doc Type: Final Report

Section 3
Physical Environment of the Major River Basins
3.3 Colorado Basin Table 3-3 Land Cover Data forthe Colorado Basin
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3.3.1 Colorado Basin Geography _ _ _ _ ~~~
The Colorado Basin, as depicted in Figure 3-9,
encompasses approximately 9,830 square miles (Crifasi
2000; CGS 2003). The largest cities in the basin are
Grand Junction (population 45,669) and Glenwood
Springs (population 8,301) (DOLA 2002).
3.3.2 Colorado Basin Climate
Because of large changes in altitude, the climate in the
basin varies dramatically from alpine conditions in the
east to semiarid in the west (Benci and McKee 1977;
USGS 1994). Figure 3-10 shows a contour plot of the
average annual precipitation throughout the basin.
Average annual precipitation ranges from less than
10 inches per year in the Grand Valley to greater than
45 inches per year in the high mountains (mainly winter
and early spring snowfall) (Apodaca et al. 1996; CGS
2003).
3.3.3 Colorado Basin Topography
Elevations in the basin range from greater than
13,000 feet in the headwater areas to about 4,300 feet
where the Colorado River exits the state (CGS 2003).
The basin's mountainous headwaters areas gradually
give way to a series of canyons and gentler terrain as the
river follows the Interstate 70 corridor toward Grand
Junction, the Grand Mesa, and the Utah border.
3.3.4 Colorado Basin Land Use
Land use in the Colorado Basin (USGS 1992) is shown
in Figure 3-11 and Table 3-3. A substantial portion of the
basin is comprised of federally owned land. Livestock
grazing, recreation, and timber harvest are the
predominant uses of federal lands. Active and inactive
mines can be found in the basin. Coal mining occurs in
the central portion of the Roaring Fork Valley and in the
lower Colorado Valley (CDPHE 2002). Rangeland and
forest are the predominant land uses in the Upper
Colorado Basin (about 85 percent) (USGS 1994).
Forested land is present throughout many parts of the
basin.
Forest 5,569 56.7% 29,577 28.4%
Planted/ 325 3.3% 13,737 13.2%
Cultivated
Barren 224 2.3% 1,219 1.2%
Open Water 114 1.2% 590 0.6%
Developed 54 0.6% 923 0.9%
Orchards/ 5 0.05% 5 0.00%
Vineyards
Wetland 1 0.01 % 80 0.08%
TOTAL 9,830 104,060
Source: USGS 1992 NLCD
3.3.5 Colorado Basin Surface Geology
The underlying bedrock in the Colorado Basin area
consists predominantly of crystalline and sedimentary
rocks. Alluvium, consisting of stream, landslide, terrace,
and glacial deposits, is present in valleys throughout the
basin (Apodaca et al. 1996).
3.3.6 Colorado Basin Surface Water
The headwaters of the mainstem of the Colorado River
are within Rocky Mountain National Park in eastern
Grand County. The Colorado River flows southwest
approximately 230 miles through Grand, Eagle, Garfield,
and Mesa Counties and exits the state at the Utah
border. Tributaries of the Colorado, including the Fraser,
Blue, Eagle, and Roaring Fork Rivers (Figure 3-9) also
drain Summit and Pitkin Counties as well as portions of
Routt, Gunnison, and Rio Blanco Counties.
The Colorado River accounts for approximately
44 percent of the streamflow leaving the state (Colorado
SEO 2003). Interstate compacts with other Colorado
basin states limit development of the basin yield.
Between 450,000 and 600,000 AF is diverted to Eastern
Colorado annually.
Numerous USGS streamflow gages are maintained in
the Colorado Basin. Six of these gages were selected to
summarize historic flows in the basin across a broad
spatial scale. The locations of these gages are shown on
Figure 3-12 along with the location of major diversions
and segments with decreed instream flow rights in the
basin. Table 3-4 summarizes the mean annual
streamflow, period of record, and drainage area for each
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