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TitleEpanet and Development. How to calculate water networks by computer
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Epanet and Development

How to calculate water networks by computer

First English Edition
October 2011

Santiago Arnalich

Page 92

Epanet and Development. How to calculate water networks by computer 83

© Santiago Arnalich Arnalich. Water and habitat

The daily consumption pattern

You have calculated what the beneficiaries consume in a whole day but the way the
water is consumed in that day is as important as the total quantity. The figure below
shows the variation of consumption according to the hour of the day for twenty urban
beneficiaries in Bolivia. Although each one consumes in a different way, tendencies
can be observed. For example, the consumption at night, from 0:00 to 6:00 is very low.

These tendencies can be summarized in the consumption pattern that you will find
on the next page. The method of construction is relatively simple:

1. Take the measurement during 24 hours in certain points. In order to have
statistical validity there have to be at least 30 points.

2. Find the average for each hourly frame, this sometimes requires the decision
to be taken as to whether an unusual consumption is deleted or not. It’s
possible, for example, that there is one in every 30 consumers that is a high
user therefore gave a peak that is not due to an error (i.e. a tea shop or car
wash). Before eliminating them you should think hard about the decision. If you
want to split hairs, you can see what values are anomalous in a statistical test
of out of range values (i.e. Grubbs).

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84 CHAPTER 4. Loading the model Helping improve Development Aid through training and consultancy.

3. These tendencies are now reflected in what Epanet calls “patterns” but we
have been calling consumption pattern. The dotted line is the average

Note that if you measure patterns of networks that are not performing correctly you can
end up with an undesirable pattern.

It is unlikely that the peak of
consumption coincides exactly with
one of the hours measured. The result
is that there is always a peak that is
overlooked. The way to take this peak
into account is to estimate shape of
the demand curve. Although there are
programs that have the option to do
this automatically, this is not the case
with Epanet. If there is very rapid
growth in the demand before and rapid
decline after an hour, as in the graph,
you can take this peak into account by
drawing it on graph paper or making a
graph with the “smoothed line” option
in a spreadsheet.

Assess yourself if it is worth the hassle to do in your network.

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