Page 94 - Water Loss Control

76 Cha pte r Se v e n

provided examples of countries where standardized and regularly compiled water
audits build the bases for a successful reduction and management of water losses.
Terms water audit and water balance are often interchanged. However, when talking
about a water audit we mean the work related to tracking, assessing, and validating all
components of flow of water from the site of withdrawal or treatment, through the
water distribution system and into customer properties. The water audit usually exists
in the form of a worksheet or spreadsheet that details the variety of consumption and
losses that exist in a community water system. The water balance summarizes the
results of the water audit in a standardized format (see Fig. 7.1).
Throughout the 1990s efforts materialized to develop a rational, standardized water
audit methodology and water loss performance indicators (PI). Part of the motivation
spurring this work was the focus on demand management and the wise use of water in
England and Wales, which was driven by competition, drought-related water shortages,
and other factors. In the late 1990s, IWA initiated a large-scale effort to assess water sup-
ply operations, which resulted in the publication of Performance Indicators for Water Sup-
1
ply Services in 2000 (a second edition of this publication was published in 2006 by IWA
2
publishing ). While this initiative included various groups assessing all aspects of water
supply operations, the Task Force on Water Loss worked specifically to devise an accept-
able water audit format and performance indicators that can be used to make effective
comparisons of water loss performance of systems anywhere in the world.
The methods put forth by the IWA Task Force on Water Loss, represent the current
“best practice” model for water auditing and performance measurement. This is not
just because of the multination process used in assembling the results, but primarily
because the work was groundbreaking in providing a clear structure for a need that
was void of knowledge throughout most of the world. Additionally, the work has been
tested thoroughly using data from dozens of countries and since its publication numerous
utilities around the globe have successfully adopted these methods as their best practice
for assessing water losses. Several countries, including South Africa, Australia, Germany,
Malta, and New Zealand have adopted the IWA best practice model for water auditing
and performance indicators as best practice for their national water loss management

Billed Billed metered consumption
authorized Revenue
consumption Billed unmetered consumption water
Authorized
consumption
Unbilled Unbilled metered consumption
authorized
consumption Unbilled unmetered consumption
System
input Unauthorized consumption
volume Apparent Customer metering
(allow for losses inaccuracies and data handling Non-
known errors revenue
errors) water
Water Leakage on transmission (NRW)
losses and/or distribution mains
Real
losses Losses at utility’s storage tanks
Leakage on service connections
up to point of customer use

FIGURE 7.1 Standard IWA/AWWA water balance. (Source: Ref. 6.)