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<br />7. Determine 50% and 75% Widths: <br /> <br />W50% ~ (500)(0.38) I 530 <br /> <br />Wi'5% " (260)(0.38) I 530 <br /> <br />= 0.:36 hours or 21.0 min <br /> <br />,,0.19 hOllrs or 11.2 min <br /> <br />W50% ahead of Qp = (0.35)(21) <br /> <br />Wi'5% ahead of Qp = (0.45)(11.2) <br /> <br />~ 7.4 min' <br /> <br />= 5.0 mill* <br /> <br />'Note: Less .than 0.6Tp = 9.6 minutes; therefore. use 7.4 minutes and 5.0 minutes <br />at W50% and W75% respectively. If the 7.4 minute:, were greater than O.6Tp. the <br />alternate procedure would have been llsed. <br /> <br />8. Sketch the prelimmry unit hydrograph (F:igure 7.6) using Tp, Qp. W50%, W75%. and <br />the portions of W50% and W75% ahead of Op determinecl above. <br /> <br /> 1000 I --I" --... <br /> '. , I TIME a TIME a <br /> __UNIT RAINFALL :: 1 INCH 0 0 " " <br /> I 5 "5 '0 " <br /> '. " 5.0 MINUTE~; 10 ,.5 " 55 <br /> 600 I <br /> f...." '. s 13.5 MINtlT~S " "6 " 40 <br /> I 20 .63 " 30 <br /> T ~"'NUT:_ 2S 350 60 20 <br /> 30 260 65 " <br />--;-800 35 210 90 6 <br /> " ,.. 95 , <br />0 Qp '" 530 cl, " 136 '00 0 <br /> so 110 <br />. <br />0 -l- =r-- . <br />- -~ ---..- <br />Il.. 400 <br /> 5.0 MINUlE,S <br /> 1.' "'NUIES 1 <br /> 200 l---- -- <br /> .,1,SSUMECl SHAPE r 11.2 AC. FT. <br /> :t I I <br /> ': '~:;1 SHAPE , 20.3 AC. FT. <br /> 0 -- - =- <br /> 0 20 .0 60 60 100 17.0 <br /> T1lrllF.. ('.!INUTES) <br /> <br /> <br />Figure '7.7 <br /> <br />Colorado Flood <br />Hydrology Manual 1-47 <br /> <br />CPI'FT <br />