The main aspects of the software tools that are currently improving or need to be improved further in the software tools are: uncertainty analysis, consideration of supply intermittency, and loss reduction analyses. Although the importance of uncertainty analysis is widely recognized in the industry, only five tools have a module for uncertainty analysis. Intermittency of the water supply is a subject of increasing interest, yet it is considered in only four tools. Whenever intermittency is of concern, normalizing the PIs to a continuous supply is necessary, and this has been included in only four tools (which consider only real losses). Normalizing the NRW and apparent losses remain unaddressed. To plan for leakage reduction, the tool Component Analysis Model is relatively comprehensive as it analyses the potential benefits of pressure management, active leakage detection, and minimizing response and repair time of bursts. However, apparent losses have still not been adequately recognized in the industry.
Association (AWWA) and published in 2000. By compiling a water audit using the standardized IWA/AWWA methodology, water utility auditors gain an understanding of the nature and extent of their system water loss volumes and, via the validation process, allows the utility to calculate the mathematical confidence in those annual volumes. Good management of any resource requires that the supplier maintains accurate records of transactions and deliveries of the commodity provided to its customers. A water audit has exactly that goal, tracking and accounting for every component of water in the cycle of delivery. The water audit typically tracks and validates the volumes of water from the site of withdrawal or treatment, through the water distribution system up to the first point of customer consumption. 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 water system. The water balance itself is a summary of all the components of consumption and losses in a standardized format. Every unit of water supplied into the system needs to be assessed and assigned to the appropriate component. Once volumes of valid authorized consumption and losses (apparent and real) have been assigned, the cost impact of these components can be calculated. Subsequently, the water utility will be able to select the appropriate tools for intervention against real and apparent losses as discussed further in Chaps. 11 to 19 of this manual.
Several effective top-down water audit spreadsheet models are available for free download. In 2006, the AWWA Water Loss Control Committee launched its free water audit software, which can be downloaded from www.awwa.org. Instructions for use of this top-down model are provided with the software; however, instructions to conduct a detailed, bottom-up water audit using the same methodology are provided in the third edition of the AWWA M36 publication Water Audits and Loss Control Programs (proposed 2008). This publication is also compiled by the AWWA Water Loss Control Committee. Table 10.1 provides an example using the AWWA free software, showing the input and output from the top-down water audit for the Philadelphia Water Department (PWD) for its fiscal year ending June 30, 2006.
The AWWA's free water audit software is an excellent tool that water utilities can utilize to start the auditing process in a top-down manner. However, as the utility progresses with more detailed, bottom-up auditing, it becomes advantageous to incorporate 95% confidence limits as discussed in Chap. 7. Table 10.2 illustrates an example of a water balance compiled using free water audit software that is available from the World Bank. The example shows the resultant statistical confidence value in each key component of the water balance.
A number of other software packages are available which offer additional features including variance analysis (Aqua Solve, LEAKS/PIFastCalcs, and the like). The Aqua Solve package is shown in Tables 10.3 and 10.4. Table 10.3 shows a balance from San Francisco Public Utilities Commission (SFPUC) and Table 10.4 shows how variance analysis can be used to identify the components which have the most impact on the aggregated uncertainty of the water loss components.
By ranking the water balance input components which have the greatest impact, the auditor can quickly identify those components that should be field validated. Obviously field validation is the best means to confirm that the output from a model truly represents field conditions. However, field measurements require time and resources (staffing, equipment) and it is often desirable to limit the extent of field validation in order to contain activities within a reasonable water audit budget. In this way, the key variables are field validated and the auditor works down the list until the desired aggregated confidence limit is reached. It is important to note at this stage that the operator should strive to model ranges of volume for each key component of water loss. Water loss volumes are not absolute volumes. 2b1af7f3a8