Chapter 3 : Reservoir models - KU Leuven

As the overflow events are strongly variable, distributions for all overflow
parameters are obtained. These distributions can be presented as a function of the
mean overflow frequency (over 27 years). The mean overflow frequency is defined
here as the number of days per year with an overflow event. In figure 3.37 the mean
overflow volume per day with overflow is shown as well as the upper limit of the 68 %
two sided confidence interval. From this figure it can be concluded that, except for
very low overflow frequencies, the mean overflow volume per day with an overflow
event is about 4 mm. However, there is a large scatter on the distribution. In figure
3.38 the variation of the mean overflow discharges with the mean overflow frequency
are shown. For higher mean overflow frequencies the mean overflow discharge will
decrease. This is mainly due to the fact that the mean overflow duration also increases
with increasing mean overflow frequency (figure 3.39). The variation of the maximum
overflow discharge within 10 minutes with the mean overflow frequency is similar to
the variation of the mean overflow discharge, but about 60 % higher (figure 3.40).
This comparison as a function of the overflow frequency shows that if the frequency
decreases only small and less severe overflow events will be avoided.
10
9
8
7
6
5
4
3
2
1
0
overflow volume (mm)
0 5 10 15 20 25 30
overflow frequency (days/year)
Figure 3.37 : Mean overflow volume per day with overflow and
the upper limit of the 68 % two sided confidence interval
as a function of the mean overflow frequency.
Chapter 3 : Reservoir models 3.43