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<br />. <br /> <br />CWCB Comment #7. <br /> <br />What are the ranges of confidence associated with the <br />statistical parameters used to determine flows? What are the <br />confidence limits at each gage for the standard Deviation, <br />Skew, and Mean Logarithm? We are especially concerned about <br />the Mean Logarithm since those values at the two gages were <br />apparently used to prepare Figure 2, which was, in turn, a <br />controlling parameter in calculating flows at various <br />locations along Clear Creek. That curve's validity is <br />obviously dictated by the confidence limits at each of the two <br />points used to construct it. How do we know basin area, and <br />not elevation, is the most significant variable? <br /> <br />Corps Response #7. <br /> <br />Confidence limits were not determined for the Standard <br />Deviation, Skew, and Mean Logarithm since the drainage area <br />relationships were based on only the two gages located within <br />the Clear Creek basin. However, the 5% and 95% confidence <br />limits for the 50 percent chance exceedence discharges <br />(approximately equal to the antilog of the mean flood <br />logarithm) are provided as follows: <br /> <br /> Lawson Discharge in cfs Golden Discharge in cfs <br /> 5% 50% 95% 5% 50% 95% <br /> Limit Exceedence Limit Limit Exceedence Limit <br />Snowmelt 1160 1030 921 1610 1460 1330 <br />Rainfall 423 352 292 999 838 702 <br />Mixed 1070 974 882 N/A N/A N/A <br /> <br />Copies of the computer printouts and graphical illustration of <br />the results are enclosed which include the confidence limits <br />associated with the entire range of exceedence frequencies. <br /> <br />It was assumed that basin area would be the most <br />significant variable in deriving the regression relationships. <br />This assumption is supported by logic and previous experience. <br />It is recognized that elevation is an important variable. <br />However, since only two gages were used in the analysis, no <br />additional independent variables could be included in the <br />relationship. <br /> <br />CWCB Comment #8. <br /> <br />How were the effects of reservoirs in the basin taken <br />into account? It is not clear in the text that the reservoirs <br />were modeled as though they were filled to the crest of the <br />spillway. That would mean their only effects in reducing <br /> <br />4 <br />