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The two reaches that included data from the South Platte River near Balzac gage were defined <br />by two separate gages, the South Platte near Balzac gage and fl1e Soufl1 Platte at Cooper Bridge <br />gage. The South Platte near Balzac gage had a record of available daily streamflow data from <br />1/ 1/ 1950 through 9/ 30/ 1980 and South Platte at Cooper Bridge has daily streamflow data <br />available after 9/30/1980. To fill the entire period of record a command file was implemented <br />>11 TSTools fllat combined fl1e records of bofll gages to estimate daily flow in the South Platte <br />River near Balzac for the entire study period. The data after 9/30/1980 was adjusted to account <br />for fl1e intermediate diversions fllat exist between the two gage locations. <br />The streamflow data for t11e Sout11 Platte at Waterton location was computed from the <br />combined inflows of Phan Creek near Louviers and the South Platte at Waterton (Table 1). The <br />>11flow was represented by these two gages because the confluence of Plum Creek and the South <br />Platte River is immediately downstream of the Waterton stream gage. <br />Missing data records for the following stream gages which defined the stream reaches had been <br />previously estimated on a monthly time step as described in the SPDSS Task 2 Technical <br />Memorandum (LRE, 2006): Plum Creek near Louviers, Sout11 Platte River near Weldona and <br />South Platte River at Balzac. To fill the missing records from these gages on a daily interval, a <br />command file was developed for use in TStools similar to t11e techiuque applied to fill data on a <br />monthly time step. T11e command files for these gages fill missing data by utilizing streamflow <br />data from a nearby gage or wifl111istorical flows from t11e same gage. An additional command <br />file was developed to fill the missing data for the South Platte P`iver at Fort Lupton gage which <br />had not been previously filled on a monthly time step using sinular filling techniques. <br />Appendix B contains the command files used to fill the missing stream flow records. <br />Missing data from the Cherry Creek at Denver, CO gage was filled using interpolation when <br />only isolated daily flow records were nussing. When fllere was nussing data for several <br />consecutive months or years, t11e missing records were estimated by computing an average flow <br />from historic flow records for the day in question using fl1e available daily flow data for fllat <br />gage in HydroBase. It was determined that utilizing linear interpolation as a filling method did <br />not accurately estimate the seasonal variation in flow when there were large periods of nussing <br />data. Therefore, filling missing records based on average daily flow patterns was determined to <br />be the most appropriate over interpolation to fill the missing daily values because it utilized the <br />pattern established on the 1listorical daily basis. <br />Missing data records for the Big Thompson River at Mout11 near La Salle w11ic11 was included as <br />an >11flow >11to one Sout11 Platte reach had been previously estimated on a monthly time step as <br />described in the SPDSS Task 2 Technical Memorandum (LRE, 2006). Appendix B contains the <br />command files used to fill the missing records. Data was filled sinular to the method utilized to <br />fill nuss>11g data for the Cherry Creek at Denver, CO gage described above. <br />Table 3 depicts t11e percentage of daily records nussing for each stream flow gage included in <br />the estimated baseflow as inflows into a reach. <br />SPDSS Phase 4 Task 46 Technical Memorandum -Final <br />0~4i 10i0~ <br />