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<br />, <br /> <br />EM 111C>-2-UOS' <br />1 Manh l~O <br /> <br />" <br /> <br />( <br /> <br />rise or lall, the corrected discharges will generally be found to result in loops of lesser size. If trial values <br />of X are applied to the corrected discharges, according to the fourth procedure for dctermining K, the <br />loops lor the best fit condition 01 K and X more nearly approach a single curve, The conversion from <br />st€adyflow discharge is approximat,ed by the square root of slope formula, <br /> <br />Q=Q..,j-d~/dx ____ _h_____ _ __:: ________m_~___ _ (21) <br /> <br />if the stage hydrographs from t.wo st.ations are available, or by the empirical Jones formula <br /> <br />Q=Q, /1+ ~hV/ot _ _ __ _ _ __.. -" -- -- -- - - -- --- on..____ - - (22) <br />-V 10. <br /> <br />or the Thomas formula <br /> <br />Q=Q, /1+ ~h/ot _ _...n. _ _.. __ __ ._w _. mh - - -- - -.- (23) <br />.,.'J I,Vw <br /> <br />if the change. in stage is measured at one station and if the wave form moves at constant velocity and <br />with no (or little) change in shape. If these approximate relationships are inadequate, use can be made <br />of r:10re precise formulas presented by Gilcrest,' Thomas," and Posey 1 or of empirical charts derived <br />from the basic data. <br /> <br />2-10 DETERMINATION OF X, a, Significance of X. The effect of variation in X on the shape <br />01 a routed flood hydrograph is illustrated in figure 4, In the case of equality of t.t and K, an X value of <br />0.5 results in a hydrograph translated through the reach without change in shape, An X value of zero <br />produces reservoir-type storage routing. <br />The symhol X bas been considered to 'iepresent a. dimensionless constant. that is an index of the <br />wedge storage in a routing reach, If it is considered that figure 5 represents a unit width of a. wide rec- <br /> <br />\ <br /> <br />15 <br /> <br />10 <br /> <br /> <br />-- <br /> <br />W <br /><.!:> <br />a: <br />~ <br />:c <br />u <br />I.fl 5 <br />o <br /> <br />o <br />o <br /> <br />5 <br /> <br />10 15 20 <br />TIME <br /> <br />subreoche.' ....ith L'>.t: K: I in eoch subreoch 1 <br /> <br />(Routings through four <br /> <br />Figure 4- <br /> <br />8 <br />