Page 107 - Water Loss Control

Evaluating W ater Losses 89

40
Range of consumption/service line/d for 56 Californian water utilities,
1988 study
35
Real losses as % of system input 25 Curved line represents real losses
30

of 60 U.S. gal/service line/d
20
15

10

5

0
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Average consumption in U.S. gals/service line/d
FIGURE 7.4 How percent real losses vary with consumption, for real losses of 60 gals/service
line/d.

consumption (pcc) are applied—as the pcc goes down, the percent water losses
goes up. Not a great incentive to demand management in its widest sense, simply
because of the choice of an inappropriate performance indicator!
Technical committees worldwide (Germany, United Kingdom, South Africa) have
recognized these paradoxes of using percentages, but perhaps most significantly the
England and Wales Economic Regulator [Office of Water Services(OFWAT)] also recog-
nized it and stopped publishing water losses statistics in percentage terms in 1998.
Water system managers who unquestioningly accept percentages as a valid measure of
technical performance in management of water losses should consider if they are fall-
ing into the same trap as Julius Frontinius Sextus, 2000 years ago—using a simple, but
inappropriate, measure to draw inappropriate conclusions.

7.7 IWA/AWWA Recommended Performance Indicators
for Nonrevenue Water and Real Losses
During the period 1996 to 2000, various IWA Task Forces undertook a detailed study to
determine the most appropriate performance indicators for different water supply pur-
poses. Table 7.4 below shows the PIs for nonrevenue water and real losses recommended
by IWA 1,2,8 converted to North American units.
The PIs are categorized by function and by level, defined as follows:

• Level 1 (basic): A first layer of indicators that provide a general management
overview of the efficiency and effectiveness of the water undertaking.