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. 4.3 Model Components The river network definition is furnished the model via a network file. The network file includes a physical description of the study area, how the stations connect, physical facilities (reservoirs, power plants, canal capacities, etc.), and supply requirement locations (for diversions, instream flow requirements, return flow points, etc.). The connection to the operational parameters is through the use of table numbers, which are then used as pointers to the data in the table file. Flow data is introduced into the model by the means of a natural flow data base file which is read by the computation program. The natural database for the Green River was derived form the ~olorado River ~imulation ~stem (CRSS) [3] model. The CRSS model flow database was converted to HYDROSS format and altered slightly to more realistically reflect conditions on the Little Snake River. The flow data in both models represents pristine monthly flow at each headwater station and at intermediate locations. In practice, the gaging station flow for a given historical period will include the effect of any man- made improvements existing at the time, and must be adjusted to reflect natural flows. The table file is the mechanism for introducing operational parameters to the model. Information on the size and capacity of Flaming Gorge is provided to the model by the table file. The file also contains information on all diversions, gains and losses The CRSS Demand Data-base file was used as a basis of many of the tables used to simulate diversions and return flows [4]. The information provided by Reclamation on the operation and physical characteristics of Flaming Gorge Reservoir, dam and power generation facilities was used to develop the network definition and tables to simulate the operation of Flaming Gorge. 4.5 Operational Criteria Flaming Gorge was modeled to operate in accordance with its authorization legislation and operational criteria as described in Chapter 3 section 3.3. The operational criteria were translated into operating rules and programmed in to HYDROSS network and tabled to assure that the basic operational objectives were achieved. The rules dictated maximum water conservation and which maintained the reservoir as full as possible to ensure that compact requirements can be met in the event of drought conditions. Within this constraint, Flaming Gorge is primarily operated for power, with other resources being addressed in individual operating objectives. 4.6 HYDROSS Simulation of Flaming Gorge The Flaming Gorge was modeled with generating facility consists of three generators with a summer season maximum operating capacity of 42 megawatts each, and a winter season maximum operation capacity of 44 megawatts [5]. Water released through these three units was modeled to range between a high of 4,200 cfs and low of 800 cfs. The maximum releases are constrained by generator capacity, and the minimum releases are controlled by an agreement with the State of Utah to provide a minimum release of 800 cfs. 4-2