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<br />DRAFT <br /> <br />* Represents results from combined 0904700 & 09046600 records <br />** station excluded from final regional analysis. <br /> <br />The values presented in Table 2.3, except those indicated as <br />excluded were used to perform multiple regressions of the form: <br /> <br />Q"=aAb <br /> <br />(2.01) <br /> <br />Where Q"is the peak discharge in cfs for a return period of n- <br />years, A is the area of the watershed in square miles, a is the <br />coefficient of the equation and b is the exponent of the equation. <br />The resulting equations are listed below: <br /> <br />Q, = 40.3Ab,." (R'=0.86) (2.02) <br />Q, = 46. o A"'" (R'=0.89) (2.03) <br />Q1O= 51.8A'''' (R'=0.89) (2.04) <br />Q25 == 62.3A.'... (R'=0.88) (2.05) <br />Q50 = 72.8A.... (R'=0.86) (2.06) <br />Q,,,,= 85.2A.... (R'=O. 84) (2.07) <br /> <br />~hese equations are representative of the entire Blue River basin <br />1n an average sense. However, looking at the results of the <br />frequency analysis shows that the upper Blue River appears to have <br />lower peak discharges than the other main drainages, the Snake <br />River and Tenmile Creek. In addition to natural characteristics, <br />man-made influences on the upper Blue River contribute to the lower <br />peaks. The most significant influences are numerous diversion in <br />the headwaters, the vast area of dredge spoils which might <br />attenuate flows and a number of small reservoirs. To develop more <br />specific equations for the upper Blue River basin, the frequency <br />curve for the combined Blue River Dillon gage (at Dillon and near <br />Dillon, 1911 1985) can be used with the general exponents <br />developed for the entire basin to transform the discharges to <br />locations with different drainage areas. The equation would be: <br /> <br />Qn = QnD( i~b <br /> <br />(2.08) <br /> <br />Where Qn is the discharge in cfs for the n-year return period, Q~ <br />is the discharge for the n-year return period near Dillon, A is <br />the area in square miles of the watershed in questions, and ~ is <br />the drainage area for the near Dillon station (119 square miles). <br /> <br />The resulting equations derived for the upper Blue River basin are: <br /> <br />Q, "'31. SA"." <br />Q, "'37. 2A".'. <br />Q.. "'42 .1A.'..' <br />Q" "'51. 2A.... <br /> <br />(2.09) <br />(2.10) <br />(2.11) <br />(2.12) <br /> <br />8 <br />