Water

Home : Sectors and Themes : Water : Library : Research and Reports : Reducing Non-Revenue Water in Asia


Reducing Nonrevenue Water in Asia
NRW-Related Concepts and Definitions1

The International Water Association (IWA), a global network of water professionals, has produced an international “best practice” standard approach for calculating a water utilities’ annual “water balance” to assess nonrevenue water and its components.
NONREVENUE WATER IN ASIA

WATER BALANCE TERMINOLOGIES

The following are definitions of principal components of the IWA water balance.

  • System Input Volume is the annual volume put into the part of a water supply system that relates to water balance calculation.
  • Authorized Consumption is the annual volume of metered and/or nonmetered water taken by registered customers, water suppliers, and others who are implicitly or explicitly authorized to do so for residential, commercial, and industrial purposes. It includes water that is exported.
  • Water Losses can be identified by calculating the difference between system input volume and authorized consumption. They consist of apparent losses and real losses.
  • Apparent Losses result from unauthorized consumption and all types of inaccuracies associated with metering.
  • Real Losses result from losses at mains, service reservoirs, and service connections (up to the point of customer metering). The annual volume lost through all types of leaks, bursts, and overflows depends on their individual frequencies, flow rates, and duration.
  • Nonrevenue Water is the difference between system input volume and billed authorized consumption, and it consists of the following:
    • Unbilled Authorized Consumption (usually a minor component of water balance)
    • Apparent Losses
    • Real Losses

Top

STANDARD WATER BALANCE

The IWA ‘best practice’ water balance can be used as the basis for both national and international performance comparisons, which is rapidly gaining international acceptance.

IWA “Best Practice” Standard Water Balance
System Input Volume Authorized Consumption Billed Authorized Consumption Billed Metered Consumption (including water exported) Revenue Water
Billed Nonmetered Consumption
Unbilled Authorized Consumption Unbilled Metered Consumption Nonrevenue Water
Unbilled Nonmetered Consumption
Water Losses Apparent Losses Unauthorized Consumption
Metering Inaccuracies
Real Losses Leakage on Transmission and/or Distribution Mains
Leakage and Overflows at Utility’s Storage Tanks
Leakage on Service Connections up to Customers’ Meters

Top

RELATED LINK

  1. The contents of this article are based on Chapter 9 of Asian Water Supplies: Reaching the Urban Poor written by Arthur McIntosh.