Answer:-
Given That:-
The 4 - hr unit hydrograph for a watershed is given.
A design storm has 1.5 cm/hr in first 2 hr and 1.0 cm/hr in the second 2 hr. The abstraction rate is 0.5 cm/hr. Base flow is 10 m3/s.
Time (hr) | 4 hr H | 4 hr | logged | Unit hydrograph | sum |
0 | 0 | 0 | |||
2 | 15 | 15 | |||
4 | 45 | 0 | 45 | ||
6 | 65 | 15 | 80 | ||
8 | 50 | 45 | 0 | 95 | |
10 | 25 | 65 | 15 | 105 | |
12 | 10 | 50 | 45 | 0 | 105 |
14 | 0 | 25 | 65 | 15 | 105 |
10 | 50 | 45 | 105 | ||
0 | 25 | 65 | |||
10 | 50 | ||||
0 | 25 | ||||
10 | |||||
0 |
Time (hr) | S-Curve ordinate | S-Curve lagged 2 hr | Difference | 2HR UH |
0 | 0 | 0 | 0 | 30 |
2 | 15 | 15 | 15 | 60 |
4 | 45 | 45 | 30 | 70 |
6 | 80 | 80 | 35 | 30 |
8 | 95 | 95 | 15 | 20 |
10 | 105 | 105 | 10 | 0 |
12 | 105 | 105 | 0 | 0 |
14 | 105 | 105 | 0 |
Calculate the total runoff hydrograph.
Given R1 = 2 1 cm/hr = 2 cm = 20 mm
R2 = 2 0.5 cm\hr = 1 cm = 10 mm
Time (hr) | UH | R1 2x | R2 | R1+ R2 | Base flow + R1+ R2 |
0 | 0 | 0 | 0 | 0 | 10 |
2 | 15 | 30 | 0 | 30 | 40 |
4 | 45 | 90 | 15 | 105 | 115 |
6 | 65 | 130 | 45 | 175 | 185 |
8 | 50 | 100 | 65 | 165 | 175 |
10 | 25 | 50 | 50 | 100 | 110 |
12 | 10 | 20 | 25 | 50 | 60 |
14 | 0 | 0 | 10 | 10 | 20 |
0 | 0 | 10 |
Coordinates of total run off hydrograph = flood hydrograph.
The 4-hr unit hydrograph for a watershed is given as below. Time (hr) 2 4 6...
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