Non-revenue water (NRW) is water that has been produced and is "lost" before it reaches the customer. Losses can be real losses (through leaks, sometimes also referred to as physical losses) or apparent losses (for example through theft or metering inaccuracies). High levels of NRW are detrimental to the financial viability of water utilities, as well to the quality of water itself. NRW is typically measured as the volume of water "lost" as a share of net water produced. However, it is sometimes also expressed as the volume of water "lost" per km of water distribution network per day.
Components and audits The International Water Association (IWA) has developed a detailed methodology to assess the various components of NRW. Accordingly, NRW has the following components:International Water Association:[www.fondazioneamga.it/public/lambertfe19maggio06.pdf ], August 2003, accessed on November 29, 2009
Unbilled authorized consumption Apparent losses (water theft and metering inaccuracies) Real losses (from transmission mains, storage facilities, distribution mains or service connections)
In many utilities the exact breakdown of NRW components and sub-components is simply not known, making it difficult to decide about the best course of action to reduce NRW. Metering of water use at the level of production (wells, bulk water supply), at key points in the distribution network and for consumers is essential to estimate levels of NRW (see Water metering).
In most developed countries, there are no or very limited apparent losses. For developing countries the World Bank has estimated that, on average, apparent losses – in particular theft through illegal connections – account for about 40% of NRW.World Bank, December 2006: The Challenge of Reducing Non-Revenue Water in Developing Countries, p. 3 In some cities, apparent losses can be higher than real losses. Reducing apparent losses from illegal connections is often beyond what a utility can achieve by itself, because it requires a high level of political support. Illegal connections are often in slums, which means that their regularization in some cases particularly affects the poor. A water audit is a key tool to assess the breakdown of NRW and to develop a program for NRW reduction. Often a distinction is made between unvalidated and validated water audits.American Waterworks Association:Water Wiser:Water Audits and Loss Control, accessed on November 8, 2009Johnson, Paul V.: Unaccounted-for water puzzle: More than just leakage. Florida Water Resources Journal, February 1996 Unvalidated water audits are desktop studies that include many estimates and their results can have an error range for real losses of ± 50% or more. Its main value is to identify where it is necessary to reduce the uncertainty of the water audit through validation. Validating water audits is a complex process that involves testing of production water meters, testing of a representative random sample of customer meters, eliminating systematic errors created through the billing process and validating the number of illegal connections through aerial mapping, field surveys or cross-references between various existing databases.Paul Fanner:Driving down water loss:validating water audits for accurate NRW management, in:Water 21, Magazine of the International Water Association, December 2009, p. 53-54 In developing countries it is rare to find utilities that have undertaken validated water audits, and even in developed countries they are not systematically used. The American Water Works Association (AWWA) has developed Water Audit Software which allows utilities to rate the overall degree of validity of their water audit data. Guidance on loss control planning is given based upon the credibility of the data and the measure of losses displayed by the water audit.American Water Works Association:Water Loss Control, retrieved on May 2, 2013American Water Works Association:M36: Water Audits & Loss Control Programs manual, Third Edition, retrieved on May 2, 2013
NRW is sometimes also referred to as unaccounted-for water (UFW). While the two terms are similar, they are not identical, since non-revenue water includes authorized unbilled consumption (e.g. for firefighting or, in some countries, for use by religious institutions) while unaccounted-for water excludes it.International Benchmarking Network for Water and Sanitation(IB-NET): Non-Revenue Water at the International Benchmarking Network for Water and Sanitation Utilities (IB-NET)
Indicators The most commonly used indicator to measure NRW is the percentage of NRW as a share of water produced. While this indicator is easy to understand and indeed has been widely used, it has increasingly been recognized that it is not an appropriate indicator to benchmark NRW levels between utilities or even to monitor changes over time. When losses in terms of absolute volume are constant the percentage of NRW varies greatly with total water use, i.e. if water use increases and the volume of losses remains constant the percentage of NRW declines. This problem can be eliminated by measuring NRW not as a share, but in terms of absolute losses per connection per day, as recommended by the International Water Association (IWA).Water 21, Journal of the IWA, April 2006, p. 30 Nevertheless, the use of percentage figures to compare levels of NRW remains common despite its shortcomings. The International Benchmarking Network for Water and Sanitation recommends to use different indicators (percentage, losses per connection or losses per km of network) together. Losses per kilometer of network are more appropriate to benchmark real losses, while losses per connection are more appropriate to benchmark apparent losses.
The concept of NRW as an indicator to compare real losses of water utilities has been criticized as flawed, particularly because real losses depend to some extent on factors largely outside the control of the utility, such as topography, age of network, length of network per connection and water use per capita. As an alternative indicator for the measurement of real losses an Infrastructure Leakage Index (ILI) has been developed. The ILI is defined as the ratio of Current Annual Real Losses (CARL) to Unavoidable Annual Real Losses (UARL).A.O. Lambert and R.D. McKenzie:Practical Experience in using the Infrastructure Leakage Index , International Water Association Conference 'Leakage Management: A Practical Approach', Lemesos, Cyprus, November 2002, accessed on November 8, 2009
Overview of NRW levels
Expressed as a share of produced water The following percentages indicate the share of NRW in total water produced:
Singapore 5% (UFW) Batam Island - Indonesia 15% (2019) - (ATB Batam) Denmark 6% Netherlands 6% Germany 7% (2005)Metropolitan Consulting Group: VEWA - Vergleich europaeischer Wasser- und Abwasserpreise, p. 4 of the executive summary The study states that its methodology allows for an accurate comparison, including water used to flush pipes and for firefighting. Japan 7% (2007)Mohamed Benouahi and Satoru Ueda:Accountable Water and Sanitation Governance:Japan's Experience, in:Water in the Arab World. Management Perspectives and Innovations, World Bank, 2009, p. 131-156, retrieved on January 6, 2011 Eastern Manila, Philippines 11% (2011), down from 63% in 1997Lanier C. Luczon and Genieson Ramos:, Introduction, 2012, retrieved from the website of the International Water Association on February 15, 2012 Tunisia 18% (2004)Private Sector Participation and Regulatory Reform in Urban Water Supply: The Middle East and North African Experience, Edouard Perard, OECD Experts' Meeting on Access to Drinking Water and Sanitation in Africa, Paris, December 1, 2006 England and Wales 19% (2005) MWA, Bangkok 25% (2012) France 26% (2005) Dhaka, Bangladesh 29% (2010)Taqsem Khan:The performance challenges of Dhaka WASA, in Global Water Intelligence:Focusing on performance, Global Water Summit 2011, p. 50-52. Italy 29% (2005) Chile 34% (2006), p. 63 Eastern Jakarta, Indonesia 42% (2016), down from 59% in 1998 Amman, Jordan 34% (2010)USAID/Miyahuna:Lost Water and Lost Revenue Reduction Program. Diagnosis, Planning and Implementation. Presentation, Amman, 14 February 2011 Mexico 51% (2003) Comisión Nacional de Agua (CONAGUA): Estadísticas del agua en México, 2007 , p. 123 Western Jakarta, Indonesia 39% (2011), down from 57% in 1998Jakarta Water Supply Regulatory Body:The First Ten Years of Implementation of the Jakarta Water Supply 25-Year Concession Agreement (1998-2008) (A Draft Translation), by Achmad Lanti, Firdaus Ali, Agus Kretarto, Riant Nugroho, Andi Zulfikar as Board Members of the Jakarta Water Supply Regulatory Body Period 2005-2008, 2009, p. 128-130 Kosovo 58%World Bank, June 2018, Water Security Outlook for Kosovo http://pubdocs.worldbank.org/en/496071548849630510/Kosovo-Water-Security-Outlook-Report.pdf Bauchi state, Nigeria 70% Yerevan, Armenia 72% (1999)Asian Development Bank, Melissa Alipalo, Anand Chiplunkar, Mai Flor: Yerevan Water Supply. Going Private Gradually - Armenia makes gains taking transitional route through private water , August 2008 Lagos, Nigeria 96% (pre-2003)Whichwaynigeria.net:Regulating to revive water supply in urban Nigeria , August 22, 2009 by JOACHIM EZEJI, accessed on November 29, 2009. The author quotes a 2003 World Bank report saying that: "Lagos State Water Corporation holds the dubious distinction of having the highest recorded level of unaccounted-for-water in the world. Only 4 percent of its water production capacity goes towards the creation of revenue."
Expressed in cubic meters per network length The following figures are expressed in cubic meters per kilometer of distribution network per day:
Netherlands 1.5 Denmark 1.6DANVA:Water in figures. DANVA's Benchmarking and Water Statistics 2010, quoting OFWAT for figures outside Denmark, retrieved on April 16, 2012 Germany (towns) 0.7–2.4, Profile of the German Water Sector , p. 55, Figures were converted from a per-hour basis to a per-day basis Germany (large cities) 2.4–5 Australia 4.4 Malmö, Sweden 5 California Water Service Company 6 Portugal 7 England and Wales 10 Helsinki 18 Penn American Water 19 Russia 20 (2006) Stockholm 21 Scotland 21.3 Illinois American Water 26 Ireland 29National Water Study , WS Atkins Ireland p. 7 Brazil 42 (2006) China 52 (2006)Greg Browder:Stepping Up: Improving the performance of ChinaÕs urban water utilities, World Bank, 2007, p. 12 Bucharest 350 in 2000 and 176 in 2007World Bank:Water in Bucharest:A Utility's Efficiency Gains under a Concession , February 2011, Viewpoint Note No. 326, by David Earhardt, Melissa Rekas and Martina Tonizz
These levels are given per km of network, not per connection.
Benefits of NRW reduction The World Bank has estimated the total cost of NRW to utilities worldwide at US$14 billion per year. Reducing by half the current levels of losses in developing countries, where relative losses are highest, could generate an estimated US$2.9 billion in cash and serve an additional 90 million people.World Bank, December 2006: The Challenge of Reducing Non-Revenue Water in Developing Countries, p. v
Benefits of NRW reduction, in particular of leakage reduction, include
financial gains from increased water sales or reduced water production, including possibly the delay of costly capacity expansion; increased knowledge about the distribution system; increased firefighting capability due to increased pressure; reduced property damage; reduced risk of contamination.Lahlou, Zacharia M.: Leak Detection and Water Loss Control, National Drinkingwater Clearinghouse at West Virginia University, 2001, p. 2 More stabilized water pressure throughout the system