Loss Of Water Globally

A standardized International Water Association's (IWA)/American Water Works Association (AWWA) water balance provides the water utility with the necessary results and understanding of the nature and extent of its water losses. Subsequently, the water utility will be able to select the appropriate tools for intervention against real and apparent losses.

Just as businesses routinely prepare statements of debits and credits for their customers, and banks provide statements of monies flowing into and out of accounts, a water audit displays how quantities of water flow into and out of the distribution system and to the customer. Yet, as essential and commonplace as financial audits are to the world of commerce, water audits have been surprisingly uncommon in the world of public water supply throughout most of the world. In places where the intrinsic value of water has not been recognized, little motivation has existed to prompt requirements for auditing and sound assessments of water loss performance. As water is becoming a more valued commodity, however, this picture is beginning to change and Chap. 4 has

Compiling a reliable water audit or water balance is the critical first step in managing water losses in public water supplies.

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 supply operations, which resulted in the publication of Performance Indicators for Water Supply Services in 20001 (a second edition of this publication was published in 2006 by IWA publishing2). While this initiative included various groups assessing all aspects of water supply operations, the Task Force on Water Loss worked specifically to devise an acceptable 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

System input volume (allow for known errors)

Authorized consumption

Billed authorized consumption

Billed metered consumption

Revenue water

Billed unmetered consumption

Unbilled authorized consumption

Unbilled metered consumption

Non-revenue water (NRW)

Unbilled unmetered consumption

Water losses

Apparent losses

Unauthorized consumption

Customer metering inaccuracies and data handling errors

Real losses

Leakage on transmission and/or distribution mains

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.)

Figure 7.1 Standard IWA/AWWA water balance. {Source: Ref. 6.)

regulations. The American Water Works Association (AWWA) Water Loss Control Committee (WLCC) has adopted the IWA water audit methodology and performance indicators as best practice in its committee report "Applying Worldwide Best Management Practices in Water Loss Control" published in the August 2003 edition of the AWWA Journal.3 The AWWA WLCC is currently in the process of rewriting the AWWA M36 manual of "Water Supply Practices, Water Audits, and Leak Detection" to incorporate the current best practice for water audits and in general water loss management. In addition the World Bank, the Asian Development Bank, and the European Investment Bank have also adopted the IWA methodology as best practice to assess water losses and determine performance indicators.

The water audit discussed in this chapter relates to the treated water distribution network and does not include the raw water transmission systems or the treatment process. The reason is that in the majority of systems the losses stemming from the distribution system represent an order of magnitude that eclipse the losses stemming from the raw water transmission systems or the treatment process. However, water losses from the raw water transmission system or the treatment process can be evaluated in a separate balance if necessary.

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    How water balancing works for water utility?
    8 years ago

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