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<br />concurrent period. The cross-correlation coefficient between <br /> <br />the two sites for the period of concurrent record is the criterion <br /> <br />to justify use of the adjustment. The minimum values of the <br /> <br />correlation coefficient, r, required for different record length <br /> <br />ratios, <br /> <br />{Nl + N2)/Nl, where Nl is the number of years when flows <br /> <br />were concurrently observed at the two sites and N2 is the number <br /> <br /> <br />of years when flows were observed at the longer record site but <br /> <br />not observed at the short record site, are given as follows: <br /> <br />r <br /> <br />{Nl + N2)/Nl <br /> <br />0.90 <br /> <br />2.0 <br /> <br />0.85 <br /> <br />3.0 <br /> <br />0.80 <br /> <br />4.0 <br /> <br />For the ungauged study areas, the regression results are <br /> <br />used to compute peak discharges for selected recurrence intervals. <br /> <br />For gauged sites, the peak discharges are obtained from the weighted <br /> <br /> <br />averages which are computed from the station values and regression <br /> <br />values for each selected recurrence interval as the following: <br /> <br /> ow = <br />where Qw = <br /> Qs = <br /> Qr = <br /> Ns = <br /> Nr = <br /> <br />(Qs x Ns) + (Qr x Nr) <br />Ns + Nr <br /> <br />weighted discharge <br /> <br />Station discharge <br /> <br />Regression discharge <br /> <br />Number of years of station record <br />used to compute Qs <br /> <br />Equivalent years of record for Qr. <br /> <br />A value of 10 years has been used for Nr as recommended by the u.s. <br /> <br />Water Resources Council. <br /> <br />-15- <br />