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<br />~,4.~
<br />D~t~~. Charles Mesa located east of Pueblo; and
<br />(3) a supp]emental water supply via the Fountain Val-
<br />ley Pipeline for Colorado Springs, Stratmoor Hills,
<br />Security, Widefield. and Fountain, which are located
<br />several miles north of Pueb]o. Altogether, Pueblo Res-
<br />ervoir provides water to about a half million people in
<br />southeastern Colorado, In addition, Pueblo Reservoir
<br />is one of Colorado's major recreational reservoirs that
<br />is used extensively for boating, fishing, and primary
<br />contact sports such as swimming. water siding. and
<br />wind surfing. The reservoir provides water to a warm-
<br />water. cool-water. and cold-water fish hatchery that is
<br />located immediately downstream from the dam. Many
<br />of the current and future uses of this multipurpose res-
<br />ervoir depend on maintaining acceptable water quality.
<br />Pueblo Reservoir is the farthest upstream, main-
<br />stem reservoir on the Arkansas River and has a drain-
<br />age area of 4,669 mi2. The surface-water quality in the
<br />upper Arkansas River Basin is affected by snowmelt
<br />runoff (the principal source of annual streamflow).
<br />rainfall runoff. mine drainage, effluents from numerous.
<br />smal]-capacity wastewater-treatment plants, ground-
<br />water inflow, and land and water use in the basin.
<br />Concerns over potential water-quality problems
<br />that could result from runoff, mine drainage. discharges
<br />of wastewater. salt loadings from return flows, and
<br />taste-and-odor problems associated with nuisance
<br />algae led to a comprehensive water-quality investiga-
<br />tion of Pueb]o Reservoir. The study was begun in the
<br />spring of 1985 by the V.S. Geological Survey in coop-
<br />eration with the Pueblo Board of Water Works, Foun-
<br />tain Valley Authority, Southeastern Colorado Water
<br />Conservancy District, Pueblo West Metropolitan Dis-
<br />trict. St. Charles Mesa Water District. and the Bureau
<br />of Reclamation.
<br />This report is the third report prepared as part of
<br />the study, The first report (Edelmann, 1988) describes
<br />the water quality of the upper Arkansas River Basin
<br />and the quality of water entering the reservoir and some
<br />of the areal, vertical. and seasonal water-quality varia-
<br />tions that occurred in Pueblo Reservoir during] 985.
<br />Some general information about potential contami-
<br />nants to Pueb]o Reservoir also is provided in the first
<br />report. The second report (Edelmann and others. ]991)
<br />contains water-quality data collected during 1985
<br />through ]987.
<br />
<br />Purpose and Scope
<br />
<br />This report describes the temporal and spatial
<br />variations of physical, chemical. and biological charac-
<br />teristics of Pueblo Reservoir and provides a discussion
<br />of water quality of the upper Arkansas River Basin and
<br />
<br />the reservoir as they relate to reservoir operations,
<br />Descriptions of the following physical, chemical, and
<br />biological characteristics of Pueblo Reservoir are
<br />included in this report: measurements of water temper-
<br />ature, specific conductance, water transparency and
<br />turbidity, dissolved oxygen, and pH; and analyses of
<br />dissolved solids, major nutrients, trace elements.
<br />organic carbon. radiochemical constituents, ch]oro-
<br />phyll a, density and relative abundance of phytoplank-
<br />ton. and phytoplankton biomass. These constituents
<br />were analyzed to provide a thorough description of
<br />water-quality conditions in the reservoir and baseline
<br />of information that can be used for future investiga-
<br />tions. Data were collected from the spring of ] 985
<br />through the fall of 1989 and are published in Ugland
<br />and others (J 988, ] 990) and Edelmann and others
<br />(199]).
<br />
<br />Description of Pueblo Reservoir and
<br />Reservoir Operations
<br />
<br />Pueblo Reservoir is a multipurpose storage facil-
<br />ity of the Fryingpan-Arkansas Project that was autho-
<br />rized by Public Law 87-590. Storage began in January
<br />1974, and the concrete and earth-fill dam built on the
<br />Arkansas River was completed in August 1975. The
<br />reservoir has a total initial storage capacity of
<br />357,678 acre-ft. Since water was first impounded in
<br />Pueblo Reservoir, reservoir storage has varied greatly
<br />because of variations in annual inflow and demand for
<br />the stored water (fig, 2). Prior to 1983, the reservoir
<br />contents ranged from 22.680 acre-ft in November 1974
<br />to ] 1] .920 acre-ft in March 1982. From early] 983 to
<br />June 1988, the reservoir contents were more than
<br />200,000 acre-ft because of greater-than-normal stream-
<br />flows from the Arkansas River. From 1985 to 1987,
<br />reservoir contents ranged from 295,480 acre-ft in
<br />February 1985 to 228,850 acre-ft in October 1987
<br />(fig. 2), During 1988 and 1989, reservoir contents
<br />decreased because of smaller streamflow in the Arkan-
<br />sas River upstream from the reservoir and large down-
<br />stream demands for stored water. Reservoir contents
<br />decreased to] 10,770 acre-ft in October ]989 (V.S,
<br />Bureau of Reclamation, written commun,. 1990),
<br />At all pool elevations, the reservoir is dendritiC,
<br />and the shoreline is irregular. At minimum pool
<br />(30,355 acre-ft), the reservoir is aboul 3.5 mi long,
<br />ranges in width from a few hundred feet to about
<br />].3 mi, and ranges in depth from a few feel at the inflow
<br />to about 72 ft at the dam. At the lop of the conservation
<br />pool (about 265,000 acre-ft or an elevation of about
<br />4.880 ft), the reservoir is more than 9 mi long. ranges
<br />in width from about 0.3 to about 2.2 mi, and has a depth
<br />
<br />4 Physlcst, Chemlc.t, .nd alotoglc.' Chs,.cte,tsllcs 01 Puebto Re.ervol" Coto,.do, 198!Hl9
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