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'001261 . Draft Task 7 Technical Memorandum . after the existing senior demands described above, but ahead of the Juniper-based instream flow right and ahead of existing junior and future demands. The only future demand treated as being senior in the model is the Hayden Station. The power plant has a senior (pre-1954) direct flow water right for 30 cfs which is more than adequate to cover existing uses at the plant as well as projected water demands beyond the 2040 long-term horizon. Future demand at the Hayden plant (demand 28) was, therefore, represented in the model as a senior demand and allowed to divert ahead of the Juniper-based instream flow right and ahead of the filling of new storage facilities. Junior Demands: These demands reflect increments to bring the baseline demand condition up to a future demand level, either 2015 or 2040. Future junior demands include demands 25 through 27, 29 through 33 and demands 35 and 36 (Table 2). These juniors have the lowest priority of all modeled demands and reservoirs and are served only after all other demands and reservoirs are satisfied. Reservoir Fill Administration The basin model was structured to operate on a water-year basis, i.e. October through September. Reservoirs in the model were allowed to fill only one time each water year up to their physical capacity; carryover storage in reservoirs was not counted against the reservoirs' annual fill limit. This simplification of true strict administration is not thought to introduce significant error since none of the modeled reservoirs approached using their full annual fill limit. However, the administration of reservoir fill may be further refined in Task 9 of this Study. Demands as Withdrawals versus Depletions Certain diversions in the basin are fully consumptive (e.g., cooling water at power plants) while others produce significant quantities of return flow (e.g., municipal uses). The majority of the demands explicitly represented in the Yampa River basin model were treated as depletions (fully consumptive) in the amounts estimated in Task 2 of the Study. There are certain exceptions, however, where demands were modeled as withdrawals and return flows. Demands which were modeled as withdrawals included municipal demands and diversions of the Maybell Canal. These demands could not be represented as simple depletions because to do so would underestimate their draft on reservoir storage and their call against upstream junior water rights. Municipal withdrawals were assumed to generate return flows within the same time step (one month) as the diversion; the percentage of municipal withdrawal actually consumed was varied seasonally. The Maybell Canal was also represented as a withdrawal but with lagged return flows. Potential Low Flow Reaches Except for. the minimum release requirements from Stagecoach Reservoir, there are no instream flow requirements on the mainstem of the Yampa River above Juniper Canyon. Juniper Canyon is the location of the modeled Juniper Project contemplated draft as converted to an instream flow right. Although instream flows on the Yampa mainstem were not explicitly targeted in the model, modeled flows in several reaches which were considered susceptible to low flow conditions were reviewed in all model runs. Included in these reviews were the reaches below the Hayden Station diversion and the reach immediately above the confluence of the Yampa River and the Williams Fork River. While low flows predicted by 6 '1;...