A water audit (domestic/household), similar to an energy audit, is the method of quantifying all the flows of water in a system to understand its usage, reduce losses and improve water conservation. It can be performed on a large scale for a city or a state as well on a smaller scale for irrigation projects, industries, and buildings. The audit can begin with an extensive approach to generate the water balance using available data and estimates which helps in identifying specific areas to concentrate in further stages.
History
Water auditing or the methodology of tracking water loss was first introduced as a concept by American Water Works Association (AWWA) in its Committee report "Revenue Producing vs. Unaccounted-for-water" in 1957. Since then many states and regional water regulatory agencies have attempted to measure water loss based upon the calculations carried out in the report but with little success. There were confusions and misunderstandings with the terminology of "unaccounted-for-water" used in the report and misleading results attained from water loss percentage calculations. In 2003, AWWA released its committee report "Applying Worldwide Best Management Practices in Water Loss Control" in which the term "unaccounted-for" was changed to "Non-Revenue" along with the percentage performance indicator.
The National Environmental Policy Act of 1970 was also a driving force leading to the development of Environmental Protection Agency (EPA) which created awareness about water conservation and efficiency. In U.K., five water companies funded the "National Leakage Initiative" which published a series of reports entitled Managing Leakage in 1994.
Importance
Water loss is a critical global problem and according to the World Bank, around 45 million m3 of water is lost every day which accounts to over US$3 billion every year. Asia alone loses half of its distribution water due to leakages in pipes. This huge amount of water loss adds strain to governments and utilities in their funding and deprives clean water to a major population which endures water scarcity. It can save money, time and effort that goes into treatment of water up to consumable standards, installation and distribution of systems.
Methods The basic methodology of any water audit involves evaluating the source, calculating the consumption, identifying the losses and measuring the performance indicators. American Water Works Association and International Water Association have established manuals that details the steps involved in conducting a water audit and they are considered to be the gold standard in water industry. Apart from these manuals, many local and state government bodies also have their guidelines for audits according to their geographical requirements.
American Water Works Association: Manual of Water Supply Practices American Water Works Association is a century old international nonprofit, scientific and educational association established in 1881 to improve water quality and supply. The Manual of Water Supply Practices (M36) explains the water audit methodology in a user-friendly manner and provides an overview of some of the best loss control techniques that can currently be implemented for a sustainable water loss control program. The manual provides detailed instructions on the audit process, which occurs at three levels a) top-down approach, b) component analysis, and c) bottom-up approach. For top-down approach, all water flow data are collected in order to calculate the water balance between input volume and the sum of consumption and losses. It is important to clearly identify system boundaries prior to the audit, defined by metering points at both input and output of a water system. Water balance calculation usually provides a guide as to how much water is lost as a result of customer meter inaccuracy, systematic data handling error and unauthorized consumption, as well as leakage. The manual also provides step-by-step tasks in conducting an audit and worksheets for top-down approach of the audit. Each task elaborates the process in quantifying each of the different flow of streams in a utility system. Instructions are also provided for water sources that are unmetered or have meters that are not calibrated or maintained for a long time. The numbers and data attained from available sources has to be adjusted at different levels due to various reasons including meter inaccuracies, changes in storage level and additional sources in distribution. In top-down approach, distribution water that is not accounted under billed authorized consumption are called as Non-revenue water as they do not bring revenue to utility or government or distribution company. Non-revenue water can be those that are used for fire hydrants, street cleaning, swimming pools, and water decorations. The losses in a water system can be a) apparent, due to inaccuracy in measurement of water that is successfully delivered, and b) real, due to leakage in system. The advantage of top-down approach is that it can be assembled relatively quickly and give a reasonable sense of utility's accountability status and the nature and extent of its losses. Performance indicators established in manual provide the auditors an insight to the loss standing in a particular functional area both at a broad and detailed levels. Top-down approach is the recommended starting point for utilities, homeowners and irrigation users to compile their initial water audit.
Bottom-up approach is usually costlier compared to top-down, as it involves more labor and resources involved in conducting the audit. It is mainly focused on identifying the apparent and real losses more accurately with actual field measurements. Apparent losses can be identified by analyzing billing systems to identify discrepancies, by performing meter calibration and accuracy test on random samples, and by assessing a sample of places for unauthorized consumption potential. Real losses are predominantly due to leakages which can be identified by various techniques and methods detailed in manual using bottom-up approach. The audit is usually the first step towards water conservation and the manual emphasizes on importance to act on the outcomes of audit and sustain the water loss control program.
International Water Association: Performance Indicators for Water Supply Systems The International Water Association, a non-profit organization, released Performance Indicators for Water Supply Systems in 2000 and since then the manual has been widely used in a number of projects for water performance assessment. The manual consists of performance indicators (PI) of water supply management along with indicators for human resources, infrastructure, operations, quality of service and economics. The manual is targeted on entities such as utilities, regulatory authorities, public administration and consumers. PIs are considered as tools that help an entity to efficiently and effectively monitor a system by simplifying assessments. The indicators facilitate assessments and analysis of progress by contributing to the quantification of performance of a system over a period of time from a specific point of view. The manual provides guidelines to prioritize the indicators on four levels based on size of the system, available resources and level of details required. The indicators to monitor performance of water resources are a) Water Resource Inefficiency (%) b) Water Resource availability (%) c) Availability of own water resources (%) and d) water reused in supply (%). The manual also details the process of calculating the water balance of a system, with definitions, examples and descriptions.
Local bodies Texas Water Development Board (TWDB) Water Loss Audit Manual for Texas Utilities was published by the TWDB in March 2008 in recognition of a House Bill enacted by the 78th Texas Legislature in 2003, requiring all utilities providing water within state of Texas to file a standardized water audit report once in five years with the TWDB. The audit methods of this manual follow the practices endorsed by American Water Works Association in its manual for water audit (M36). TWDB encourages utilities to conduct the audit every year although the House Bill only requires once every five years. The tasks involved in a top-down approach, water balance calculations and performance indicators are all same as that of M36. The manual also lists down bottom-up approach of auditing for utilities that heavily rely on estimates and lack reliable data. It also recommends using bottom-up approach to validate the preliminary water audit data attained from top-down approach. The assessment table in the manual using a 1-5 scale helps in developing a score of certainty for each data component used in the audit, with 1 being low degree of certainty and 5 being the highest. The entire water audit can be assessed similarly and provided a validation score on a scale of 85. A validation score of less than 40 is considered to be preliminary and utility companies are required to improve the accuracy of data collected. The goal of audit is to achieve a high validation score using practices listed out in both top-down and bottom-up approaches that reflects high level of confidence in the water audit results.
California Department of Water Resources (CDWR) The Water Audit Manual prepared by the CDWR is in accordance with AWWA's M36 Manual, created in February 2016 to provide guidance to utilities and distribution systems in conducting water loss audits. The state of California passed a Senate Bill (SB No. 1420) in 2014 which requires water suppliers to submit an audit once in every five years as part of urban water management plans.
South Florida Water Management District Water Efficiency and Self-Conducted Water Audits at Commercial and Institutional Facilities: A guide for Facility Managers is a comprehensive guide that is applicable for all users, especially in Florida, to improve water efficiency in commercial and institutional facilities. The guide provides step-by-step methodology of conducting an audit for identifying opportunities to improve water conservations in facilities such as office buildings, hospitals, hotels and motels, schools, restaurants, laundries, and car washes. Benchmarks are provided for annual water use in each of these facilities to provide a quick initial assessment of water use to the users. The audit categories are divided into Basic and Advanced, to be chosen depending upon the level of experience and expertise available in conducting the audits. The basic audit category specifies background and description, audit steps, worksheets, and post-audit guidance for different equipment and aspects inside a facility such as meters and submeters, leak detection, utility bills, kitchen water use, cooling towers, irrigation systems and rain sensors. The advanced audit procedures provide an in-depth understanding of some of the areas covered in basic audits which guides the users in identifying future water use, expenses and savings, and payback period of savings after implementing the improvements. To further improve the efficiency of water audits, guidelines are provided to a) prepare water balance of the facility, accounting for all water use from its source to all of the applications, b) create historical water use profile using bills that can point out fluctuations in water use, c) identify alternative water sources on-site for e.g., rainwater harvesting, boiler condensate and treated gray water/ waste water.
Ministry of Water Resources, India