Yampa River Basin Water Resources Planning Model Final Report

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ASY_002, and ASY_003) in the basin that were not modeled explicitly. The geographical areas represented by each structure are shown in Table 4.3.1b. TABLE 4.3.1B Areas Represented by Aggregated Reservoirs ARY 001 Water Districts 57&58 ARY 002 Water District 44 ARY 003 Water Districts 54 & 55 ASY 001 Hydrologic Unit 14050001 ASY 002 Hydrologic Unit 14050002 ASY 003 Hydrologic Unit 14050003 Parameters related to the physical capacity of the reservoirs included dead storage, where applicable, total active storage, and area - capacity tables. For the explicitly modeled reservoirs, these data were obtained from either the Division Engineer or the reservoir owners. For the aggregated reservoirs, the data were estimated based on storage decrees and Task Memo 2:09 -12, "Consumptive Use Model Non - Irrigation Consumptive Use and Losses in the Yampa River Basin, as described in Appendix D.11. The initial yampaT.res file was modified manually to reflect the operational ownerships within each reservoir. The reservoir account ownership information was obtained from interviews with the division engineer, the assistant division engineer, the local water commissioners, and in most cases the owner /operator of the subject reservoirs. A more detailed discussion of the operations of these reservoirs is presented in Appendix C, Section 10. Each account in the explicitly modeled reservoir was tied to a diversion structure that had rights to reservoir water. For situations in which the owner of storage water irrigates land under more than one ditch system, an assumption was made that the storage account will be allocated equally to each ditch system. Although this procedure may not accurately reflect actual use of reservoir storage water from year to year, it was considered adequate for purposes of the Yampa Model, particularly since the amounts of storage water so allocated were relatively small (typically less than 300 acre - feet). For ' each diversion structure having storage rights, the cumulative storage water available from each individual ownership is summarized in Appendix C, Section 10. All data required to construct the yampaT.res file were obtained from either the Division engineer or directly from the Owners. The One Fill Rule Administration date was set to April 1 for all explicitly modeled reservoirs, and October 1 for the aggregated reservoirs. Phase IIIa enhancements that impacted the reservoir station file include adding three aggregated reservoirs and three aggregated stockponds. Appendix D.11 describes these Phase IIIa enhancements. 4.3.2 Net Evaporation File - yampaT.eva The evaporation file (yampaT.eva) contains annual evaporation data (12 average values for every year). I Reservoirs 4 -12