The Sediment Transport Model and its Applications - Sediment Transport in Irrigation Canals: A New Approach - page 188

Figure 7.6 shows the behaviour of the actual and equilibrium concen-
tration as a function of time and place along the 10-km long canal. The
incoming sediment load is 200 ppm and the actual and equilibrium concen-
trations are derived from Brownlie's predictor method. The decrease after
the start of the simulation is very sharp, namely from 200 ppm to an equi-
librium value of about 108 ppm. The decrease becomes gentler with time
and moreover it will move in a downstream direction. The figure shows the
concentration immediately after the start of the simulation and after 30,
60 and 90 days. After 90 days the actual concentration is about 112 ppm
at a location 3 600 m from the intake. Along the whole canal the actual
concentration is always slightly larger than the equilibrium concentration
at any point.

250

200

150

100

50

0

0 2000 4000 6000 8000 10000

Distance (m)

Figure 7.6. Changes in the
actual and equilibrium
concentration as a function of
place and time according to
Brownlie's predictor.

C-eq at 0 days C-act at 0 days

C-eq at 30 days C-act at 30 days

C-eq at 60 days C-act at 60 days

C-eq at 90 days C-act at 90 days

Figure 7.7 shows the behaviour of the sediment deposition as a function
of time and place along the 10-km long canal. The incoming sediment load
is 200 ppm and due to the fact that the actual concentration is higher than
the equilibrium concentration the sediment will deposit on the bottom,
starting from the intake. Next the deposition will move in a downstream
direction and at the same time the height of the deposition will increase in
the area where sediment has already been deposited. The slope of the front
of the deposition will also become gentler when it moves in a downstream
direction. The observations for the changes in concentration and move-
ment of the deposition are comparable for the three sediment transport
predictors. Figures 7.5 and 7.6 are based on Brownlie's predictor and are
given as examples.
The sediment deposition in the canal as a function of a larger sed-
iment diameter is presented in Table 7.4 for the Brownlie predictor.
The table shows the total volume of sediment deposition after 90 days