Yampa River Basin Water Resources Planning Model Final Report

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and evaporation impacts on gaged streamflows. The contents are also used in the historical reservoir target file for calibration. The following assumptions were made to create the EOM reservoir content data file: • If an observation for the last day of the month was available from the CRDSS database, it was used directly as the EOM value. • If an observation for the last day of the month was not available from the CRDSS database, the observation closest to the last day of the month within 15 days of the last day of the month was used. • If no observations existed within 15 days of the last day of the month, a search for the nearest observation forward and backward in time from the last day of the month was made, and a linear interpolation was made to obtain the EOM value. • The period prior to the construction of a reservoir was filled with values of zero. It was assumed that the first date encountered in the database was the date of construction • End -of -month content for the aggregated reservoirs was assigned as follows: 100 percent full from October to June, 75 percent full at the end of July, 25 percent full at the end of August, and empty at the end of September. This schedule was developed to simulate reservoir use as a supplemental irrigation supply during late summer. • End -of -month content for aggregated stockponds was estimated as full at all times, because historical data are unavailable. Appendix C, Section 7.3 discusses the alternate data sources for each reservoir. Table 4.3.3a presents the data period available for each explicitly modeled reservoir as well as target levels. TABLE 4.3.3A Reservoir EOM and Target Data Reservoir Period of Record Operational Target Stillwater 1950 -1993 Full Yamcolo 1980 -1993 Full Allen Basin 1909 -1993 Full Sta ecoach 1988 -1993 Full Lake Catamount 1977 -1993 Full Fish Creek 1956 -1993 Full Steamboat Lake 1974 -1993 Full Lester Creek 1974 -1993 Full Elkhead 1976 -1993 Full Phase IIIa enhancements that impacted the reservoir end -of -month content file included adding three aggregated reservoirs and three aggregated stockponds. Appendix D.11 describes these Phase IIIa enhancements Reservoirs 4 -14