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<br />001172 <br /> <br />35 <br /> <br />Reservoir storage accessed by thermal.electric demands has been prioritized in the model over <br />the three existing reservoirs. Craig Station demands are met first.by the 8,310 af pool in Elkhead. Any <br />remaining unsatisfied Craig Station demand, as well as the entire Hayden Station demands ar'e then met <br />from the 9,000 af pool in Stagecoach Reservoir. if this is insufficient, the 5,000 af pool in Steamboat <br />Lake will be used. To meet the demands of the Hayden power generation unit. Finally, if thermal. <br />electric demands are still not met the 4,000 af mixed use pool in Stagecoach Reservoir can be accessed. <br /> <br />Model runs including an enlargement at Elkhead Reservoir allow all Craig.area demands to <br />access the additional storage volume. The minimum instrealTI_ flow (Link 121) is ranked lower than <br />(junior to) the Elkhead Reservoir enlargement to reflect the assumed transfer of the Juniper priority to <br />the enlargement. <br /> <br />Agricultural demands and coal gasification water demands do not have access to existing <br />reservoir storage. The coal gasification demand may be given access to enlargements or future storage <br />capacity. <br /> <br />MODEL CALIBRATION AND VERIFICATION <br /> <br />The initial calibration of the Yampa model was performed using the historical gage record data <br />and historical demands. In terms of the model data file, this meant turning off all present level and <br />future incremental demands and letting the model reproduce the gaged flows on which it is based. <br />Modeled flows at the atcs representing the Steamboat Springs and Maybell gages were compared to the <br />flows. historically recorded at those gages. In a sense, the model at this stage W'4S hardwired to produce <br />the Maybell flows, however this exercise produced a V'.luable check thai insured overall mass balance in <br />the system was being preserved and that no reservoir operations or other arcs were incorrectly beirig <br />manipulated. . . <br /> <br />Additional model verification occurs after every successful model run. Verification is performed <br />by in~uring mass balance is maintained anC;! in the manner which the user wishes. Checking mass <br />balance in the model involves extracting the flow of muhiplc arcs and tracking water through the model. <br />All demands, inflows and decrees are checked. An effort was made to make an accounting of water in <br />arcs in all critical areas of the network and under a variety of hydrologic conditions. For example, <br />Stagecoach Reservoir operations occurring in the model were closely evaluated to insure proper <br />releases were made for instream flow requirements; power generation! and 'reservoir drawdown during <br />the Winter months. <br /> <br />Structure of Model Scenarios <br /> <br />[n defining model scenarios, particular altcntion was given to the relative priorities of the <br />proposed instream flow right, existing and future storage rights, and future water demands. The <br />structure of the scenarios was chosen to help answer the following fundamental questions: 1) is there a <br />sufficient legal and physical supply to meet all futu.re demands?, 2) if there is an insufficient legal supply, <br />can the Juniper subordination make up the shortages?, and 3) if there is an insufficient physical supply, <br />can reservoir releases (from existing and/or proposed projects) make up the shortages? These <br />questions may be addressed by careful seleetion of priorities assigned to the proposed instream flow <br />right, to storage in reservoirs, and to fiJlure demand increments. <br /> <br />Model scenarios have been defined to help identify the best administrative and/or <br />developmental strategie:) to meet various demand levels in the basin. Each model scenario is comprised <br /> <br />