A 85-km2 catchment has a 4-h concentration time, with isochrones at 1-h intervals resulting in the following time-area histogram:
| Time (h) | 0-1 |
1-2 |
2-3 |
3-4 |
| Area (km2) | 17 |
21 |
31 |
16 |
Use the time-area method to calculate the outflow hydrograph from the following storm pattern:
| Time (h) | 0-1 |
1-2 |
2-3 |
3-4 |
4-5 |
5-6 |
| Total rainfall (cm/h) | 1 |
2 |
5 |
4 |
3 |
1 |
The runoff curve number is CN = 81. Use a spreadsheet. Verify with
ONLINE ROUTING 06. Note that the latter only takes effective rainfall.
Use the Clark method to derive a 2-h unit hydrograph for a catchment with the following time-area diagram:
| Time (h) | 0-1 |
1-2 |
2-3 |
3-4 |
4-5 |
5-6 |
| Area (km2) | 20 |
40 |
60 |
40 |
24 |
16 |
Use Δt = 1 h and K = 3 h. Use a spreadsheet and verify with ONLINE ROUTING 07.
Use Example 10-3 in the text (cascade of linear reservoirs) to test ONLINE ROUTING 08.
Then route the effective rainfall hyetograph of Example 10-3 (with time interval Δt = 6 h)
using: (a) K = 12 h and N = 4 and (b) K = 18 h and N = 5. Discuss the results.
A 1-h unit hydrograph derived from measured data has the following ordinates:
| Time (h) | 0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 | 14 |
| Inflow (m3/s) | 0 |
7 |
22 |
48 |
60 |
90 |
74 |
47 |
28 |
17 |
10 |
6 |
4 |
3 | 2 |
Assuming a time of concentration tc = 6 h, calculate the linear reservoir storage constant K in the Clark method.