Question

2. (20pts) The discharge rates for an 1-hr unit hydrograph are given (see Table 1). Develop a 3-hr hydrograph with 2 in prepicitation (a rough sketch is optional) Table 1. 1-hr UH Time, hr Runoff (cfs) 0 0 100 2 250 3 150 4 0 1 Working table:

Answer 1

solution 13 hr UM Time, hr. I 1-hr UH I lag by ! 3-hr Hyrdrograph Lag by 2hr. - +2+ 1 hr. x2 + + 0 0 100 33.33 66.66 2501 100 116.667 233.33 3 150 250 1 100 166.667 333.33 4 150 - 250 133.333 266.66 5 150 50 100 + 6 o Here, first of all we devewp 3-hr UH by lagging 1-hr UH. and finally 3-hr Hydrograph with 2-inch precipitation will be fermed by multiplying 2 in with ordinates of 3-hr uh. 3hr Hydinograph with 2 in precipitation • 1 lag. 2nd lag. 3hrour. I 2 3 6