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<br />the variation of velocity from stream reach to stream reach and specified contributions of <br />excess (as ratios of basin-mean contribution) in different portions of the basin. Another <br />advantage is that the unit duration can be changed without requiring a new time-area <br />relation to be developed. <br /> <br />The runoff from the contributing areas (between the isochrones) which has been <br />translated to the outflow location is in units of volume (in-mi 2 or mm-km 2). The <br />conversion to proper units of discharge is made through the relationship: <br /> <br />_ Kaj <br />I j - /!J <br /> <br />(IV-9) <br /> <br />where: <br /> <br />I; = ordinate in proper units of discharge (cis, cms, etc.) of <br />the translation hydrograph at the end of period i <br /> <br />a; = ordinate in units of area-depth of excess (in-sq mi, mm-sq km, <br />etc.) of the translation hydrograph at the end of period i <br /> <br />K = conversion factor to convert a ; to I ; (to convert in-sq mi to <br />cis, K = 645; to convert mm-sq km to cms, K = .278 etc.) <br /> <br />At = time period of computation interval in hours. <br /> <br />The routing of the translation hydrllgraph through storage at the outflow location <br />is accomplished as follows: <br /> <br />0; = CI;+(1-C)0;_1 <br /> <br />(IV-10) <br /> <br />where: <br /> <br />0; = outflow from the basin at the end of period i <br /> <br />I; = inflow or runoff from each area at the end of period i <br /> <br />C = dimensionless routing constant <br /> <br />The routing constant, C, is determined for prism type storage as: <br /> <br />c= 2/!J <br />2 R+ /!J <br /> <br />(IV-11) <br /> <br />Colorado Flood <br />Hydrology Manual <br /> <br />7-42 <br /> <br />ffi'JFf <br />