Question

Storm data were collected for a 810-acre basin. Approximations for the wadi-flow, rainfall and runoff cumulative mass curves are shown in the following figure. 5.00 500 485 4.75 450 445 4.50 4.25 4.00 425 Cumulated DRO -Cumulated gross rainfall Wadi-flow 400 3.75 3.50 350 3.25 315 3.00 295 300 2.75 Cumulated Gross rainfall and DRO in inches 2.50 250 Wadi flow (cfs) 2.25 215 2.00 200 1.75 1.50 155 150 140 1.25 1.00 100 90 0.75 75 0.50 55 50 35 25 25 0.25 25 0 0.00 5:00 7:00 9:00 15:00 17:00 19:00 11:00 13:00 Time (hr:min) 1. Find the Phi-index for this storm. Assume that the rainfall amount before the direct runoff began is equal to the initial abstraction. Use 1-hr time interval in your calculations. 2. Determine the lag-time, time base and time of rise for the storm. 3. Develop a 1-hr UH for this watershed.

Answer 1

ta 4hr. 9 = 2.8colha R = 25.2 x 1060 3. A a 28olme 6 R = 2502 x 10 280X106 gem. P = 20884 z uaem fraRR 1102-9 505 molho 4

Ans Ihruh Dosive. 3 h7 ch. 7=3 hr Dalho OSA-CUIVE, Lag - Ihr Q SA #SB Lag - 3 ho for resulting DRH, REm = '710 = 3/133 Time lho utt Laly Ihr g-curve add SA Iscusve Lag 3hr SB-cuve SASB ood of stut BjA58 UD = SA-512X1 0 %3 5 5 513 5. 8 13 13 2 18 6 3 5. 13 18 21 5 18 16 3 4 1873 16/3 3½ 413 wo 22 a - 6 13 ¢િ 0 2014 .22 4 .