Improvements and assessments of water auditing techniques

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2009-05-15

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Water auditing is an emerging method of increasing accountability for water utility systems. A water loss audit according to the methodology of the International Water Association (IWA) is applied to a major North American water utility, San Antonio Water System (SAWS), which is already a leader in conservation policies. However, some modifications to the auditing process are needed for this model?s application to a North American utility. These improvements to the IWA methodology include: calculating system input volume from multiple methods of measurements as well as numerous input points, incorporating deferred storage consumption (in this case aquifer storage and recovery) principles into the auditing process, calculating a volume of unavoidable annual real losses (allowable leakage) for a system with varied pressure zones, and defining procedures for assessing customer meter accuracy for a system. Application of the improved IWA audit method to SAWS discovered that its system input volume is being significantly undermeasured by current practices, current water loss control programs are very effective, customer accounting procedures result in large volumes of apparent loss, and current customer meter accuracy is adequate but could be marginally improved. Application of the audit process to the utility is beneficial because it facilitates increased communication between utility departments, assesses shortcomings in current policies, pin-points areas needing increased resources, and validates programs that are performing well.

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