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<br />0016
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<br />Purpose and Scope
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<br />This report presents a compilation of w~ter-quality data for Pueblo
<br />Reservoir and for the upper Arkansas River basin that were collected from June
<br />1985 through November 1987 as part of the water-quality study. Results of
<br />onsite measurements of light transparency at ,26 sites in Pueblo Reservoir
<br />and onsite measurements of water temperature, pH, dissolved oxygen, and
<br />specific conductance from numerous depths at 26 sites in Pueblo Reservoir are
<br />presented in this report. In addition, measurements of turbidity and
<br />analyses of major ions, nutrients, trace elements, total organic carbon,
<br />radiochemicals, phytoplankton, chlorophyll a, and zooplankton for selected
<br />sites in the reservoir and chemical analyses of sediment cores collected from
<br />23 sites in the reservoir are reported. Finally, analyses of inorganic
<br />chemical constituents collected from the Arkansas River upstream and
<br />downstream from the reservoir also are presented.
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<br />Description of Pueblo Reservoir
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<br />Pueblo Reservoir is the farthest downstream eastern-slope storage
<br />facility of the Fryingpan-Arkansas project, a multipurpose water development
<br />authorized by Public Law 87-590. The chief purpose of the project is to
<br />divert unappropriated water from the western:slope of the Rocky Mountains for
<br />use on the more populated and water-short ea~tern slope. Pueblo Reservoir
<br />derives almost all of its contents from water entering through the Arkansas
<br />River, which is comprised of native and transmountain flow. The reservoir is
<br />formed by a concrete and earth-fill dam on the Arkansas River about 6 mi west
<br />of Pueblo. The climate at Pueblo Reservoir is characterized by small
<br />quantities of annual precipitation with periodically intense thunderstorms,
<br />high evaporation rates, moderate-to-high winq movement, low humidity, and a
<br />large daily range in temperature (Phillip E. 'Flores Associates, Inc., 1975).
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<br />The reservoir has a total storage capacity of 357,678 acre-ft. This
<br />total capacity includes 30,355 acre-ft of dead and inactive capacity, which
<br />comprises the recreation pool; 234,347 acre-ft of conservation pool, which is
<br />used in regulating transmountain and native water for municipal, industrial,
<br />and irrigation uses; 65,952 acre-ft of joint~use pool, which must be vacated
<br />and available for flood control from April 15 to November 1 each year; and
<br />27,024 acre-ft of exclusive flood-control capacity. The top of the exclusive
<br />flood-'control pool is the crest of the spill~ay at an elevation of 4,898.7 ft.
<br />The crest of the dam is 26 ft above the crest of the spillway and would
<br />temporarily hold an additional 131,500 acre-it of flood flows (U.S. Bureau of
<br />Reclamation, 1977).
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<br />Storage in Pueblo Reservoir began in January 1974, and the dam was
<br />completed in August 1975. Since impoundment, reservoir elevation, surface
<br />area, and storage have varied greatly because of inflow and demand for the
<br />stored water. Prior to 1983, after apprecia~le storage was attained, the
<br />reservoir contents varied from 22,680 acre-ft in November 1974 to
<br />111,920 acre-ft in March 1982. Between 1983 !through 1987, reservoir contents
<br />were greater than 200,000 acre-ft as the resQlt of greater than normal flows
<br />from the Arkansas River (U.S. Bureau of Recl~mation, written commun., 1988).
<br />During the data-collection period, the end-oi-month Pueblo Reservoir contents
<br />ranged from 228,850 acre-ft, to 278,740 acre-it (table 1).
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