Page 139 - Water Loss Control

CHAPTER 10

Modelling Water Losses

Julian Thornton

Reinhard Sturm
George Kunkel, P.E.

10.1 Introduction
Quantities of the various water loss volumes occurring in a water utility can be approxi-
mated by employing a mathematical representation, or model, of the loss values. Depend-
ing upon the type and nature of the apparent or real losses being modeled, a model can
be a simple spreadsheet of estimates of loss volumes attributed to a specific type of loss
occurrence, or it can be a complex set of calculations that rely upon a number of data
inputs to calculate a reliable quantity of loss. Models are an excellent tool to assist the
operator with the preparation of a water audit and water loss management planning;
however they should be used with care and due diligence. Models are not magic nor do
they give us hind sight or act as a crystal ball; they are only as good as the concepts they
employ, the data that is put into them, and the skill
and experience of the user; training in their use is
essential. So care should be taken to ensure that field Good data in means good
data captured and coefficients and variables used rep- data out!
resent real conditions as closely as may be necessary
for a result of required accuracy. If accountable data is
not available estimated data may be used, however,
the model should be notated with comments reflect-
ing the estimated inaccuracy for each component and
calculating the final weighted potential inaccuracy. 95% confidence limits is
Many industry standard water loss control models used in order to assign confi-
now incorporate the use of 95% confidence limits, dence to each input compo-
which are applied to each component of data input nent and to calculate aggre-
and calculated for each component of data output. gated confidence in the final
Further information on the use of 95% confidence lim- result.
its is covered in Chap. 7. This chapter presents exam-
ples of some basic water loss models.
Modeling flows in pipe networks and components of consumption has been an inte-
gral part of hydraulic network analysis modeling (hydraulic models) for over 30 years, but in

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