Page 55 - Water Loss Control

What is Necessary to Contr ol the W ater Loss Pr oblem? 37

In 2001, the American Water Works Association (AWWA) conducted a comprehen-
sive survey of state and regional water loss standards, policies, and practices entitled
3
“Survey of State Agency Water Loss Reporting Practices.” The survey report concluded
that even though a reasonable number of state and regional agencies hold a water loss
policy, targets and standards vary widely from agency to agency. The survey confirmed
that the structures in place to monitor drinking water supply efficiency are superficial in
nature, of limited sophistication (in most cases “unaccounted for water” percentage is
the sole performance indicator), and include scarcely any auditing or enforcement mech-
anism to validate the performance of drinking water utilities. The study clearly identi-
fied that in most cases the agencies do not provide incentives for achieving the required
targets nor do they take action for failure of meeting targets. A very important finding of
this study was that it is necessary to refine current definitions, measures and standards
for evaluating water losses in the United States. The establishment of a uniform system
of water accounting, with valid and reliable data, was proposed by this study.

4.2.6 Current Water Loss Management Practices
The starting point for successfully managing water losses is to accurately assess water
supply and consumption volumes by conducting a standardized IWA/AWWA water
audit. Many water audits are performed by utilities in the United States annually, but
they lack uniformity. The audit methods used, the performance indicators and expres-
sions of water losses calculated, and the time intervals between audits vary signifi-
cantly from utility to utility. The majority of water utilities do not use the IWA water
audit methodology recommended by the AWWA Water Loss Control Committee
(WLCC). Therefore, it is impossible to accurately compare water losses between utilities
since the assessment is not uniform. The historic indicator used to describe water losses
(% volume of nonrevenue water) is highly unreliable and inappropriate. This percent-
age is unduly influenced by the denominator (system input volume) resulting in under-
stated losses for water utilities with growing populations and overstated losses for
utilities with contracting populations. Also, this simple percentage reveals nothing
about specific loss volume quantities and costs, which are two of the most important
parameters in the analysis.
The following simplified example clearly demonstrates how misleading and inap-
propriate percentage figures are when used as performance indicator for water loss
management. In our example, we look at a standard U.S. water utility with 20,000 resi-
dents (no commercial or industrial customers) and an average per capita consumption
of 400 gal/cap/d with a total metered consumption of 2920 mg/year. Assuming the
utility has 325 mg of real losses per year the utility has a total system input of 3245 mg/year.
The percentage loss figure for this utility is therefore 10%. If the same utility reduces
the per capita consumption to 200 gal/cap/d through a successful demand side conser-
vation program the total yearly metered consumption is reduced to 1460 mg. With no
reduction in real losses the total system input is therefore reduced to 1785 mg/year, which
results in a percentage loss figure of around 18%. This simple example explains why
expressing water losses as a percentage of system input volume is a poor performance
indicator.
North American utility with typical per capita consumption of 400 gal/cap/d:
Total system input volume: 3245 mg
Total consumption volume: 2920 mg
Total losses: 325 mg