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Q. No. 3 For a watershed comprising of 5000+Your Class No. hectares in area, the rainfall and runoff data are summarized belo

Day-1 22 Day-2 3 20 21 23 24 1 2 4 5 Rainfall Data Day Hour Intensity (mm/hr) 0.5 0.5 0.5 2.7 1.0 5.2 1.7 1.3 1.1 1.3 Day-1 1

Take class no. = 180

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Answer #1

STEP 1:

Base flow seperation from surface runoff, 0.59 m3/s. You will get DRH. Then find area under DRH, calculated by excel. It gives the volume of runoff. Divide it by catchment area, you will get Effective rainfall depth or runoff depth. (unit cm for ER)

Then divide DRH ordinates by runoff depth, it gives the ordinates of 4 HR UH.

TIME HRS SURFACE RUNOFF BASE FLOW DRH AREA UNDER DRH 4HR UH
DAY 1 8 -12 0.56 0.59 -0.03
12 -8 0.61 0.59 0.02
16 -4 0.61 0.59 0.02
20 0 0.59 0.59 0 0 0
24 4 0.66 0.59 0.07 504 0.164390766
DAY 2 4 8 3.35 0.59 2.76 20376 6.481693053
8 12 4.75 0.59 4.16 49824 9.769508369
9 13 4.82 0.59 4.23 15102 9.933899135
12 16 4.25 0.59 3.66 42606 8.595288613
16 20 2.4 0.59 1.81 39384 4.250675516
20 24 1.25 0.59 0.66 17784 1.549970078
24 28 1.1 0.59 0.51 8424 1.197704151
DAY 3 4 32 0.94 0.59 0.35 6192 0.821953829
8 36 0.89 0.59 0.3 4680 0.704531854
12 40 0.84 0.59 0.25 3960 0.587109878
16 44 0.79 0.59 0.2 3240 0.469687902
20 48 0.74 0.59 0.15 2520 0.352265927
24 52 0.7 0.59 0.11 1872 0.258328346
DAY 4 4 56 0.68 0.59 0.09 1440 0.211359556
8 60 0.65 0.59 0.06 1080 0.140906371
12 64 0.64 0.59 0.05 792 0.117421976
16 68 0.62 0.59 0.03 576 0.070453185
20 72 0.59 0.59 0 216 0
24 76 0.59 0.59 0 0 0
SUM 220572
AREA OF CATCHMENT 51800000
ER DEPTH 0.004258 m
0.425815 cm

Step 2:

Find the 4 HR UH oridinates for 2 hr interval. ex. for 2hr, (0.16439+0)/2 = 0.08219.

Find the ordinates of S curve(SA) by adding the previous all ordinates, ex, S (4hr) = 0+0.08219+0.16439 = 0.24658.

Find the ordinates of 6hr lagged S curve(SB1) and 12 hr lagged S curves(SB2) by shifting the S curve.

(SA-SB)*(D/T) will give T HR UH ordinates. ex, (SA-SB1)*(4/6) will give 6 HR UH ordiantes.

HRS 4 HR UH SA SB 6HR SB 12HR (SA-SB) 6HR (SA-SB) 12HR (SA-SB)*(D/T)6HR (SA-SB)*(D/T) 12HR
0 0 0 0 0 0 0
2 0.082195 0.082195 0.082195383 0.082195 0.054797 0.027398
4 0.164391 0.246586 0.246586149 0.246586 0.164391 0.082195
6 3.323042 3.569628 0 3.569628058 3.569628 2.379752 1.189876
8 6.481693 10.05132 0.082195 9.969125728 10.05132 6.646084 3.35044
10 8.125601 18.17692 0.246586 17.93033567 18.17692 11.95356 6.058974
12 9.769508 27.94643 3.569628 0 24.37680213 27.94643 16.2512 9.315477
13 9.933899 37.88033 10.05132 0.082195 27.82900822 37.79813 18.55267 12.59938
14 9.182398 47.06273 18.17692 0.246586 28.885806 46.81614 19.2572 15.60538
16 8.595289 55.65802 27.94643 3.569628 27.71158624 52.08839 18.47439 17.3628
18 6.422982 62.081 37.88033 10.05132 24.20066917 52.02968 16.13378 17.34323
20 4.250676 66.33167 47.06273 18.17692 19.26894619 48.15475 12.84596 16.05158
22 2.900323 69.232 55.65802 27.94643 13.57398038 41.28557 9.04932 13.76186
24 1.54997 70.78197 62.081 37.88033 8.700968391 32.90164 5.800646 10.96721
26 1.373837 72.1558 66.33167 47.06273 5.824129989 25.09308 3.882753 8.364359
28 1.197704 73.35351 69.232 55.65802 4.121511343 17.69549 2.747674 5.898497
30 1.009829 74.36334 70.78197 62.081 3.581370256 12.28234 2.38758 4.094113
32 0.821954 75.18529 72.1558 66.33167 3.02948697 8.853617 2.019658 2.951206
34 0.763243 75.94853 73.35351 69.232 2.595025661 6.716537 1.730017 2.238846
36 0.704532 76.65307 74.36334 70.78197 2.289728524 5.871099 1.526486 1.957033
38 0.645821 77.29889 75.18529 72.1558 2.113595561 5.143083 1.409064 1.714361
40 0.58711 77.886 75.94853 73.35351 1.937462597 4.532488 1.291642 1.510829
42 0.528399 78.4144 76.65307 74.36334 1.761329634 4.051058 1.17422 1.350353
44 0.469688 78.88408 77.29889 75.18529 1.58519667 3.698792 1.056798 1.232931
46 0.410977 79.29506 78.4144 76.65307 0.880664817 2.641994 0.58711 0.880665
48 0.352266 79.64733 78.88408 77.29889 0.763242841 2.34844 0.508829 0.782813
50 0.305297 79.95262 78.88408 77.886 1.068539978 2.066627 0.71236 0.688876
52 0.258328 80.21095 79.29506 78.4144 0.91589141 1.796556 0.610594 0.598852
54 0.234844 80.4458 79.64733 78.88408 0.798469434 1.561712 0.532313 0.520571
56 0.21136 80.65716 79.95262 78.88408 0.704531854 1.773072 0.469688 0.591024
58 0.176133 80.83329 80.21095 79.29506 0.622336471 1.538228 0.414891 0.512743
60 0.140906 80.97419 80.4458 79.64733 0.52839889 1.326868 0.352266 0.442289
62 0.129164 81.10336 80.65716 79.95262 0.446203507 1.150735 0.297469 0.383578
64 0.117422 81.22078 80.83329 80.21095 0.387492519 1.009829 0.258328 0.33661
66 0.093938 81.31472 80.97419 80.4458 0.340523729 0.868923 0.227016 0.289641
68 0.070453 81.38517 81.10336 80.65716 0.281812741 0.728016 0.187875 0.242672
70 0.035227 81.4204 81.22078 80.83329 0.199617359 0.58711 0.133078 0.195703
72 0 81.4204 81.31472 80.97419 0.105679778 0.446204 0.070453 0.148735
74 0 81.4204 81.38517 81.10336 0.035226593 0.317039 0.023484 0.10568
76 0 81.4204 81.4204 81.22078 0 0.199617 0 0.066539
78 81.4204 81.31472 -81.4203979 -81.3147 0 0
80 81.4204 81.38517 -81.4203979 -81.3852 0 0
82 81.4204 81.4204 -81.4203979 -81.4204 0 0
84 81.4204 0 -81.4204 0 0
86 81.4204 0 -81.4204 0 0
88 81.4204 0 -81.4204 0 0
0 0
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