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SPDSS Task 4 Memorandum <br />November 23, 2004 <br />For accounting purposes, Coors applies a fill forward methodology to diversion data for <br />missing records between readings. In a telephone conversation with State hydrographer <br />Bob Cooper it was learned that the State does not apply the fill forward method to the <br />continuously monitored station data for Station STCTLTNCO. Instead, the State <br />hydrographer applies a linear interpolation for days in between recorded diversion <br />measurements. Application of two different filling routines by two sources of data could <br />explain discrepancies in diversion data between various sources. <br />Comparison of the four sources of data indicate significant differences, with percent <br />differences as high as 65 percent and averaging about 30 percent. Administrative records <br />for Structure 3604658 and Structure 0704682 are not consistent with one another and are <br />sporadically consistent with Coors records and continuously monitored data for Station <br />STCTLTNCO. Straight Creek Tunnel is subject to numerous legal conditions, as <br />discussed in the operating memorandum prepared for Straight Creek Tunnel as part of the <br />SPDSS Task 4. It is possible that administrative records for Structure 3604658 and <br />0704658 reflect these legal conditions. As such, diversion records for Structures <br />3604658 and 0704658 are not considered accurate representations of physical water <br />transported into the South Platte Basin through Straight Creek Tunnel. <br />• For the operational period of 1973 to 2002, the monthly diversion data for <br />Straight Creek Ditch was not complete. Prior to 1995, no reliable diversion <br />measurements were available. Diversions for 1993 back through 1973 were filled <br />with the average of the Station STCTLTNCO data. <br />• Daily records are available through HydroBase from 1995 through 2002. Prior to <br />1995, daily records are not available. <br />• As a result of the variety of diversion data sources available, a StateMod format <br />data file (STCTLJNCOfilled. stm) was created for Straight Creek Tunnel. <br />• For future data acquisition, the recommended source for Straight Creek Tunnel <br />diversion records is the continuously monitored data at Station STCTLTNCO. <br />Vidler Tunnel <br />Vidler Tunnel began diverting water to the South Platte basin in 1969. <br />Continuously monitored streamflow data for Station 09047300 are available for <br />daily and monthly diversions from 1971 through 2001. <br />Monthly diversions were made available from the January 23, 2001 W.W. <br />Wheeler and Associates letter to Glenn Porzak from 1969 through 1999, however, <br />there are no corresponding daily diversions associated with this data. The data <br />obtained from the W.W. Wheeler and Associates letter to Glenn Porzak is similar <br />to continuously monitored streamflow data and administrative data, after 1984. <br />Prior to and including 1984, there are discrepancies between the Wheeler data and <br />the Station and Structure data. The reason for these discrepancies is not clear. <br />The source of the diversion data in the Wheeler letter is unknown. <br />Page 13 of 19 <br />