Environmental Engineering Reference
In-Depth Information
The simulation results of the two scenarios will be compared with the
deposition in the canal without any provision to trap the sediment over
the first 1 000 m (Case 1 with a sediment inflow of 150 ppm). Scenario 1
(deepening) holds less sediment than Scenario 2 (widening
B
=
14 m)
for the same flow and sediment conditions of Case 1. After 90 days
Scenario 1 has accumulated much more sediment than the canal without
any sediment control over the first 1 000 m. The controlled deposition
by the two scenarios is especially effective during the first part of the
simulation period (about 60 days).
Figure 7.10 presents the sediment depositions over the first 1 000 m
of the canal with and without controlled deposition (scenarios 1 and 2).
This figure also gives the deposition if the canal is widened to 12 m (the
same increase in the wetted area as the deepening). Table 7.5 gives the
volumes of deposited sediment after 90 days together with the equilibrium
concentrations near the headworks at the start and at the end of the simu-
lation period. The deepening and the widening (
B
12 m) which have
the same wetted area at the start of the simulation show comparable
=
10000
8000
6000
4000
2000
Figure 7.10. Sediment
deposition in the irrigation canal
with and without controlled
deposition (deepening and
widening of the bottom over
the first 1 000 m).
0
0
30
60
90
Time (days)
No sediment trap
Deepening
Widening
Table 7.5. Total amount of sediment deposition over the whole canal length and the equilib-
rium concentration for the cases with and without measures to control the deposition over
the first 1 000 m of the canal (
Q
=
25.75 m
3
/s and
c
=
150 ppm).
Widening
Widening
No control
Deepening
B
=
12 m
B
=
14 m
Total volume of sedimentation (m
3
)
5 063
8 180
7 622
10 708
after 90 days
Equilibrium concentration (ppm) for
108
56
65
37
x
=
0 and
t
=
0day
Equilibrium concentration (ppm) for
147
148
147
146
x
=
0 and
t
=
90 days
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