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<br />001165 <br /> <br />28 <br /> <br />Several of the future demand increments represent future municipal water requirements. These <br />municipal demands were represented as withdrawals rather than depictions.' Depictions were <br />converted to withdrawals by dividing by a monthly consumptive use percl:l1tage. The monthly <br />consumptive use patterns was taken from patlerns typically found in other municipalities. In the model, <br />return fiows from municipal withdrawals are returned to the river immediately downstream of the <br />diversion and in the same time period. <br /> <br />All increments of demand were disaggregated on a monthly basis. Monthly demands are <br />required input for CRAM. Monthly disaggregation was based on typical water use patterns for each of <br />the different demand types. Municipal and industrial demands were disaggregated based on typical <br />municipal patterns. Agricultural demands were distributed only throughout the growing season on a <br />typical seasonal pattern. Out-of-basin water exports are for agricultural purposes and consequently <br />follow agricultunil use, patterns. Mining uses are assumed to follow the same temporal pattern as <br />municipal use. Thermal-electric and coal-gasifieation demands were assumed to follow a pattern typical <br />of power plant cooling requirements. <br /> <br />To the degree possible, demands were placed in the model network where they most likely will <br />occur. Depletions were allocated to various points in the network according to spatial distribution <br />factors. These spatial factors are described in more detail in the Task 2 Technical memorandum. In <br />short, the model attempts to represent the physical reality of the system as accurately as possible. The <br />one exception to this approach, the handling of cenain tributary demands, was described above. <br /> <br />Future demands synthesized in Task 2 are summarized in Tables 4-6 and 4-7. These tables also <br />provide insight to how the synthesized demands are represented in the Yampa lIasin Model, Le which <br />Task 2 demands correspond to which modeled demand and to which node of the model network they <br />are assigned. The reader may also refer to the Yampa River lIasin Model network diagram (Figure 4-2). <br /> <br />Model Operation <br /> <br />At the most fundamental level, computations in the Yampa River Basin Model are driven by the <br />priorities assigned to the various arcs in the network. The model algorithm allocates water to arcs in <br />descending order of their priorities in an effort to maximize the total vaiue of now in the network <br />(computed as the sum of flow times priority over all arcs). At a higher level. more sophisticated kinds of <br />operations can be simulated by the manipulation of priorities on specific arcs based on seasonal targets <br />or descriptors of system state; certain common types of operations, e.g., reservoir evaporation and <br />storage carryover, are automated in the CRAM network modeling system. <br /> <br />The two general types of operations represented in the Yampa River basin model are the <br />allocation of water on the basis of water rights priorities and the storage and release of water from <br />reservoirs. These operr.tions are discussed below. <br /> <br />Relative Water Right Priorities <br /> <br />The use of gage flow hydrology in the Yampa River Basin Model implies that all existing water <br />uses reflected in that gage hydrology are senior to all water rights that are expli-:itly represented in the <br />model. The key water right that will be explicitly rcprcsented is, of course, the Juniper right as <br />transformed to an in stream flow right. <br /> <br />._~;..;;;;ii <br />