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<br />INTRODUCTION TO THE UPPER COLORADO RIVER BASIN
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<br />20 40 60 KILOMETERS
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<br />The Upper Colorado River Basin
<br />encompasses about 17,800 square
<br />miles. The primary river, the Colo-
<br />rado River, originates in the moun-
<br />tains of central Colorado and flows
<br />about 230 miles southwest into
<br />Utah. The basin is composed of
<br />two physiographic provinces: the
<br />Southern Rocky Mountains and the
<br />Colorado Plateau (fig, I). The
<br />topography varies from rugged
<br />mountainous regions in the east to
<br />
<br />
<br />The Colorado Plateau contains warm, saline
<br />streams that drain sedimentary geologic settings.
<br />(Photograph by Jeffrey Deacon, U.S. Geological
<br />Survey.)
<br />
<br />
<br />Colorado
<br />Plateau
<br />Physiographic
<br />Province
<br />
<br />Agriculture is a major land use in the
<br />Colorado Plateau, (Photograph by
<br />Scott Mlze, U.S. Geological Survey.)
<br />
<br />
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<br />high plateaus bordered by steep
<br />cliffs along valleys in the west.
<br />Because of differences in altitude
<br />of about 10,000 feet from east to
<br />west, the climate ranges from
<br />alpine conditions to semiarid/arid
<br />conditions. Precipitation ranges
<br />from 40 inches or more per year at
<br />high elevations in the eastern part
<br />of the basin to less than 10 inches
<br />per year at low elevations in the
<br />western part of the basin (fig. 2).
<br />
<br />
<br />Urban development is occurring in areas of the
<br />Southern Rocky Mountams. (Photograph by
<br />Scott Mize, U.S. Geological Survey.)
<br />
<br />o
<br />I
<br />o
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<br />Snowmelt Runoff Dominates
<br />the Streamflow in Many
<br />Areas of the UCOL
<br />
<br />The amount of water derived
<br />from the winter snowpack gener-
<br />ally determines the magnitude and
<br />quality of streamflow for the
<br />UCOL. Streamflows are typically
<br />highest in the spring and lowest
<br />
<br />
<br />Cool and clear mountain streams are present
<br />in the forested areas of the Southern Rocky
<br />Mountains. (Photograph by Scott Mize,
<br />U.S. Geological Survey.)
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<br />60 MILES
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<br />Streams have been affected by runoff and dis-
<br />charge from past and present mined areas.
<br />(Photograph by Jeffrey B. Bails, U.S. Geologi-
<br />cal Survey.)
<br />
<br />Figure 1. The combinations of physiography and land use produce different environments found in the UCOL.
<br />Physiographic provinces from Fenneman, 1946.
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<br />Introduction to the Upper Colorado Basin 3
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