Tamarack Ranch Recharge Project Water Rights

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• 4.2.2 Other Parties Analysis and Comparison Numerous parties analyzed the data from these tests and a rather wide range of streambed parameters were derived. Analysis of these tests was performed by the following entities: • Colorado State University, (CSU, 2005 and 2006) • Hydrosphere Resource Consultants for the City of Boulder (Hydrosphere, 2006) • Water & Environmental Systems Technology, Inc. for the City of Centennial (W &EST, 2006) Table 3 summarizes the aquifer and streambed parameters derived by all parties for both the Stieb and Dinsdale tests. Inspection of Table 3 indicates that the parameters derived from the Stieb test were moderately consistent. However the Dinsdale APT results varied significantly depending upon the party doing the analysis. Site conditions for the Dinsdale APT were much more complex than at the Stieb APT, thus requiring more complexity and detail in the analysis. 4.3 Revised Tamarack Recharge Model To address the issue of streambed leakance, the original Tamarack Recharge Model was revised by replacing -the - constant- head - stream _ boundary with a stream boundary (Prudic, 19_89_). No pumping or irrigation recharge was included for the north side of the South Platte River. Earlier • work on the Original Tamarack Recharge Model demonstrated that there is little impact on calculated Project stream accretions or well depletions by neighboring groundwater operations (CDOW and NCWCD, 2003). The Revised Tamarack Recharge Model was run numerous times using a wide variety of streambed parameters. Table 4 summarizes the calibration results of the modeling runs. Inspection of Table 4 indicates that the calibrations of the Revised Tamarack Recharge Model using streambed leakances in the range of 1.69 to 400 day -1 are reasonably close to the calibration for the original model. The calibrations become worse as the streambed leakance is decreased. Using a streambed leakance of 0.011 day -1 does not provide a reasonable calibration. Figure 2 is a graph showing the stream depletion generated from the Revised Tamarack Recharge Model for varying streambed parameters. Figure 2 was derived based on proposed well WR -13, originally located approximately 600 feet from the South Platte River, pumping for 30 days at a rate of 2000 gallons per minute (gpm). Based on this review of the aquifer testing and modeling, CDOW proposed the following methodology be used to calculate stream depletions for those Project wells located within 900 feet of the South Platte River (CDOW, June 7, 2006). • Calculate stream depletions for each Project well within 900 feet of the South Platte River using the Revised Tamarack Recharge Model. • Use a stream leakance of 20 day as model input for the stream input. • Create a URF for each well based on the model output. 12 'Page