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<br />9. Determine required hydroqraph volume- watershod area. x 1 ,nch of runoff: <br /> <br />Unit Hydrograph Vol'Jme ~ (243 acres)(1 incll)(1 foot/12 Inches) = 20.2 acre-'eE~t <br /> <br />10. Planimeter or digitize tile preliminary unit 11ydrograph from Step to determine its <br />volume. Adjust the recession limb of the unit Ilydrograph l'nit its volume is within 5% of <br />the calculated unit hydrograph volume of 20.2 acre-feet trom Step 9. This is the final unit <br />hydrograph. <br /> <br />11. Multiply the excess precipitation value at the top of Column :l of Table7-9 by eacl, of <br />the unit hydrograph ordinates and put in Column3 for the corresponding time. Next <br />multiply the excess precipitation value in Column 4 by each of the unit hydrograph <br />ordinates and place in Column 4 lagged by one time increment from the corresponding unit <br />hydrograph time. Proceed to multipy each of ttw excess precipitation values times the unit <br />hydrograph ordinates, each !:Ime lagging the new hydrograph by one more time unit. <br /> <br />12. Table 7-9 shows the computations of the storm hydrograpll and Figure 7.8 'ihoVls <br />graphically, the development of the storm hydroqraph from the unit hydrograph and excess <br />precipitation values. <br /> <br />Table 7-9 <br /> <br /> Excess Precjpit~ <br />TimEt <br />(mlrl) UH 04 09 31 15 06 05 OJ <br />11) 12) 13) (4) (5) (61 (7) (8) (9) <br />5 115 5 <br />10 345 14 10 <br />15 528 21 31 36 <br />20 463 18 48 107 17 <br />25 350 14 42 164 52 7 <br />30 260 10 32 144 79 21 6 <br />35 210 8 23 108 69 32 17 ~I <br />40 168 7 19 81 52 28 26 10 <br />45 138 6 15 65 39 21 23 Hi <br />50 110 4 12 52 32 16 18 14 <br />55 88 4 10 43 25 13 13 10 <br />60 70 3 8 34 21 10 10 a <br />65 55 2 6 27 16 l....8 8 EI <br /> -- <br /> <br />Colorado Flood <br />Hydrology Manual <br /> <br />7-48 <br /> <br />3.tion in :nches <br /> <br /> 0= <br /> 5\c' <br />02 G3 -yc <br />(14) (15 :15: <br /> - <br /> -- - <br /> 1. <br /> 2 <br /> 2. <br /> -- - <br /> 2 <br /> -- -- <br /> 2 <br /> .-- - <br /> l' <br /> 1 <br /> .-- .- <br /> 1 <br /> - <br />3 1 <br /> .-- -- <br />10 3 1 <br /> <br />,- <br />.J <br /> <br />-1-- <br /> <br />03 03 03 :)3 <br />110) (11; 112) 1\3) <br /> <br />24 <br />8:3 <br /> <br />90 <br /> <br />/9 <br />92 <br /> <br />GO <br /> <br />3 <br />10 <br /> <br />23 <br /> <br />3 <br /> <br />93 <br />/7 <br /> <br />16 10 <br /> <br />3 <br /> <br />14 16 10 3 <br />10 14 16 10 <br />8 10 14 16 <br /> <br />61 <br /> <br />47 <br />32 <br /> <br />DR!.!;:! <br />