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<br />001881
<br />
<br />Simulations using a single-reservoir model indIcated that no significant
<br />water-temperature stratification would occur in most reservoirs because of iimlted
<br />reservoir storage. The model simulation also indicated that there could be a re-
<br />duced range in water temperatures in most of the proposed reservoirs, such as the
<br />proposed Juniper Reservoir, where the inflow water temperature could range from
<br />OoC to 260C, while the unregulated outflow water temperature could range from 40C
<br />to 180c. In addition, the model simulations indicated that the range of specific-
<br />conductance values could be less in reservoir outflows than in reservoir inflows.
<br />
<br />INTRODUCTION
<br />
<br />The Yampa River basin in northwestern Colorado and south-central Wyoming
<br />(fig. 1) is being affected by accelerated rates of coal-resource and associated
<br />economic development, which will have a direct impact on the quantity and quality
<br />of the water resources of the basin. The projected water demands from this devel-
<br />opment will not only increase the water-supply requirements but redistribute the
<br />timing of demands from the traditional water-use patterns. Several potential im-
<br />pacts will result as a consequence of mining, processing, transport, and within-
<br />basin conversion of coal and the associated residential and commercial growth
<br />(Steele and others, 1979; Weatherford and Jacoby, 1975; Udis and Hess, 1976).
<br />
<br />To meet these projected demands, considerable interest has been expressed and
<br />plans proposed for additional development of the surface waters of the Yampa River.
<br />basin (fig. 1). Currently (1979), there is little regulation of streamflow by res-
<br />ervoirs in the basin. The main use of surface water during April, May, and June;
<br />when 60 to 70 percent of the annual stream runoff occurs, is for irrigation of hay
<br />meadows, grasslands, and grain fields. As part of 18 surface-water projects,
<br />35 major reservoirs (larger than 2,000 acre-feet or 2.47 hm3) have been proposed.
<br />The overal I effect of these proposed reservoirs on the Upper Colorado River Basin
<br />is not known and will not be addressed in this report. Different Federal and State
<br />agencies, however, including the U.S. Bureau of Reclamation (1976; 1980), have
<br />written plannIng documents for the Upper Colorado River Basin, for which these
<br />report results may serve as useful Input. The total proposed reservoir capacity
<br />in the Yampa River basin is about 2.18 million acre-feet (2,690 hm3), which is
<br />41 percent greater than the mean annual outflow from the basin. This contrasts to
<br />a current (1979) aggregate storage capacity of 54,000 acre-feet (66.6 hm3) or
<br />approximately 2.5 percent of the total proposed reservoir capacity.
<br />
<br />This report describes the results of an investigation in which three computer
<br />models were used to evaluate different levels of the proposed reservoir develop-
<br />ment. One model simulated streamflow conditions with alternative multireservoir
<br />configurations; a second model simulated the dissolved-solids concentrations at
<br />various locations in the basin; and a third model used streamflows and dissolved-
<br />sol ids concentrations to simulate the water-qual ity conditions. within certain pro-
<br />posed reservoirs. This study was designed to demonstrate the application of
<br />computer-modeling technIques in evaluating impacts of proposed reservoirs. Hence,
<br />the configurations of proposed reservoirs considered in the analysis were not
<br />exhaustive; rather, reservoirs were selected to depict a range of potential loca-
<br />~ions and storage capacities. This is one of several investigations evaluating the
<br />
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