Environmental Engineering Reference
In-Depth Information
The deposition in the canal has been analysed to see if the incom-
ing sediment load is constant. Two cases have been evaluated, namely a
constant inflow of 200 ppm and one of 300 ppm during the whole irri-
gation season. The simulation shows that a continuous flow gives more
sedimentation than a rotational flow in this specific case. In view of the
small differences the results are presented in Figure 7.24. The difference
between a sediment concentration that changes with the water inflow and
a constant sediment inflow is small for this canal system.
1000
750
500
250
0
0
10
20
30
40
50
Figure 7.24. Sediment
deposition in the canal network
as a function of time for
continuous and rotational flow
and for two concentrations,
according to Ackers-White.
Time (days)
rotat. - 200 ppm
cont. - 200 ppm
rotat. - 300 ppm
cont. - 300 ppm
A further investigation of the influence of maintenance activities
on the behaviour of the sediment in the canal network with rotational
flow resulted in minimal differences in sedimentation between an ideally
maintained canal and a poorly maintained canal. The results are in line
with the data discussed in Section 7.6.
7.9 CASE 7 EFFECT OF THE DESIGN OF CONTROL
STRUCTURES ON THE HYDRAULIC BEHAVIOUR
AND SEDIMENT TRANSPORT
Overflow and undershot structures have different effects on the hydraulic
behaviour of an irrigation canal and on the sediment transport by the canal.
The SETRIC model is a helpful tool to analyse the effect of well-designed
overflow structures (without a gate) on the sediment transport process
when there are fluctuations in the discharge. This case will present the
difference between hydraulically well and hydraulically poorly designed
flow control structures. This type of analysis will be helpful to finalize
Search WWH ::
Custom Search