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-- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . of the gaging station analyses be used for discharge estimates. The results of the gage analyses may be extended to other locations using Equation 2. Based on the stated limits of Equation 2, the results for station 09073700 may be extrapolated to drainage areas between approximately 3 and 12.5 square miles. The results for station 09074000 may be extrapolated to areas between 20.5 sq miles and the confluence point with the Roaring Fork River at Aspen (approximate drainage area of 43 sq miles). For drainage areas between 12.5 and 20.5 square miles, discharge values may be determined by interpolation of results at the two gaging stations based upon drainage area. For drainage areas less than 3 square miles, a detailed hydrologic analysis is recommended as the CWCB regional regression equation appears to underpredict discharges for smaller drainage basins on this stream system. Ivanhoe Creek. Gaging station records exist for two locations on Ivanhoe Creek. The USGS gage, Ivanhoe Creek Near Nast, Co. (station no. 090776lO), has only 7 years of record (1976-82) which was deemed insufficient for meaningful analysis. A second gage, Ivanhoe Creek Near Norrie (station no. 09077600) was maintained from 1964 to 1976 and has 13 years of record. Though still a minimal period of record, frequency analysis has been carried out for this gage and the computed 100-year discharge is 260 cfs. Regional regression analysis using Equation 1 indicates a discharge rate of 394 cfs for the same location and event. Because gaging station records are very limited, it is recommended that the more conservative results of the regional regression analysis be used for analysis of 1 DO-year discharges on Ivanhoe Creek. North Fork of Frvingpan River. The USGS intermittently maintained the gaging station, North Fork Fryingpan River, Near Norrie, Co. (station no. 09078500) for a period of 40 years between 1911 and 1982. Frequency analysis has been carried out for this station and the computed 100- year discharge is 1,100 cfs. Regional regression analysis for the gage location using Equation 1 indicates a very similar 100-year discharge rate of 1,190 cfs. Because the results of the frequency analysis are site specific and based upon a relatively long period of record, it is recommended that these results be used in lieu of the regional regression equation approach. Equation 2 may be used to extrapolate the results of the frequency analysis to other locations within the stated limits of 0.5 to 2 times the drainage area at the gage. For areas outside these limits, a detailed hydrologic analysis would provide the best results. In lieu of such an analysis, the regional regression approach of Equation 1 could be applied. Comparison of this equation to historical data from the USGS gaging station indicates fairly good agreement between the two approaches. Owl Creek. The USGS maintained the gaging station Owl Creek Near Aspen. Co. (station no. 09076520) for a period of 14 years between 1975 and 1989. Though a minimal period of record, frequency analysis has been carried out for this gage data and results in a l00-year discharge of 117 cfs. Regional regression analysis for the gage location using Equation 1 indicates a substantially higher l00-year discharge rate of 312 cfs. Because gaging station records are so limited, it is recommended that the more conservative results of the regional regression analysis be used for determination of l00-year discharge rates on Owl Creek. Approximate Streams With No Gage Data. For all other streams studied by approximate methods. in the 1988 PIS, it is recommended that either detailed hydrologic analysis or the regional regression approach of Equation 1 be utilized for the determination of 100-year 6