Laserfiche WebLink
<br /> <br />in t .' Also, it is possible to refine the curve by considering the variation of velocity <br />from stream reach to stream reach and specified contributions of excess (as ratios of <br />basin-mean contribution) in different portions of the basin. Another advantage is that <br />the unit duration can be changed without requiring a new time-area relation to be <br />developed. <br /> <br />The runoff from the contributing areas (between the isochrones) which <br />has been translated to the outflow location is in units of volume lin-mi 2 or mm-km 2). <br />The conversion to proper units of discharge is made through the relationship: <br /> <br />I; = K a . I 6t <br />, <br /> <br />(9) <br /> <br />where: <br /> <br />I; = ordinate in proper units of discharge (cfs, 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 i to I i (to convert in-sq mi to <br />cfs, K = 645; to convert mm-sq km to cms, K = .278 etc.) <br /> <br />6t = time period of computation interval in hours. <br /> <br />The routing of the translation hydrograph through storage at the outflow <br />location is accomplished as follows: <br /> <br />o. = C I . + (1-C) 0, <br />I I 1- <br /> <br />(10) <br /> <br />where: <br /> <br />o i = outflow from the basin at the end of period i <br /> <br />I; = inflow or runoff from each area at the end of period <br /> <br />C = dimensionless routing constant <br /> <br />The routing constant, C, is determined for prism type storage as: <br /> <br />C = 26t <br /> <br />(11 ) <br /> <br />7-32 <br /> <br />-- <br /> <br />