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<br />
<br />Elevations in the basin range from about 4,670 ft above sea level at Pueblo
<br />to 14,433 ft at Mount Elbert in Lake County, the highest peak in Colorado.
<br />A transition from the mountains to the plains occurs between Canon City and
<br />Pueblo.
<br />
<br />Climate in the drainage basin is affected greatly by differences in ele-
<br />vation. Mean annual precipitation ranges from less than 12 in. in the plains
<br />to more than 40 in. at the crest of the highest mountains (Crouch and others,
<br />1984). Much of the precipitation in the plains is from intense summer
<br />thunderstorms. Precipitation in the mountains results in the formation of a
<br />deep snowpack that accumulates during the winter months and melts and runs off
<br />during the spring and early summer. Storm runoff and snowmelt result in a
<br />large percentage of annual streamflow that occurs during a relatively short
<br />time (Abbott, 1985).
<br />
<br />Ground cover in the basin varies from alpine-type flora around the
<br />mountain peaks to various species of grass and cacti in the lower regions.
<br />National forests cover about one-third of the area. At lower elevations,
<br />pinon pine, juniper, scrub oak, and brush occur frequently along the rocky
<br />ridges and some of the canyons, while cottonwood trees, willows, and various
<br />types of brush occur in the flatter areas along streams (Federal Water
<br />Pollution Control Administration, 1968). The smaller areas that drain
<br />directly into Pueblo Reservoir (pl. 1) are characterized as open, rolling
<br />plains with numerous uncontrolled washes and gullies.
<br />
<br />Most of the population and related activities are concentrated along the
<br />broad, gently sloping terrain near the Arkansas River (Crouch and others,
<br />1984). The principal towns are Leadville, Buena Vista, Salida, Westcliffe,
<br />Canon City, and Pueblo West (pl. 1). In 1980, there were about 58,000 people
<br />residing in the area (U.S. Bureau of the Census, 1981). The area is not heav-
<br />ily industrialized. The principal land use in the area is ranching. Histor-
<br />ically, the economy of the area in the vicinity of Leadville was dominated by
<br />mining of precious metals, but most of the mines are now (1988) abandoned.
<br />This area has produced large quantities of beryllium, coal, copper, gold,
<br />lead, molybdenum, silver, thorium, tungsten, uranium, vanadium, and zinc.
<br />Other industries in the basin include tourism and manufacturing of bulk cement
<br />and gypsum wallboard. The area is serviced by railways and highways that
<br />parallel the Arkansas River through the basin.
<br />
<br />The Arkansas River derives most of its streamflow from melting of snows
<br />that accumulate in the mountains from October to May and flow from inbasin
<br />tributaries and transmountain diversions to the Arkansas River in the spring
<br />and summer (fig. 2). Springs contribute minor quantities of water to stream-
<br />flow in the area (Crouch and others, 1984). Runoff from summer thunderstorms
<br />at lower elevations can contribute substantial quantities of streamflow for
<br />short periods. The streams, other than the Arkansas River, that drain
<br />directly into Pueblo Reservoir include Rush Creek, Turkey Creek, Peck Creek,
<br />Rock Creek, Boggs Creek, and a few unnamed tributaries (pl. 1). These streams
<br />are, for the most part, ephemeral or intermittent, and their flows are derived
<br />from springs and precipitation. Under usual streamflow conditions, the quan-
<br />tity of flow contributed to Pueblo Reservoir from these streams is negligible.
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