WATER LOSS IN NORTHWEST GEORGIA

Water-loss glossary

Definitions used throughout this project. A million gallons is abbreviated MG.

Audit terms and measures

Water supplied: Water entering the audited distribution system: water from the utility’s own sources plus imports, minus exports, with documented supply-meter corrections. Check the audit boundary before comparing systems.
Water loss audit: An annual accounting of water entering a system, authorized use, and estimated losses. It combines measurements, calculations, and estimates. It is not a survey locating every leak.
Water balance: The accounting relationship between supply, authorized consumption, apparent losses, and real losses. All components must cover the same period and system boundary.
Real losses: Physical leakage, breaks, and overflows within the audited system before customer consumption. In a top-down audit this volume is calculated as a residual, rather than measured at every leak.
Apparent losses: Water used but not properly registered or accounted for because of customer-meter inaccuracies, data handling errors, or unauthorized consumption. The water may reach a user even though the accounting misses it.
Non-revenue water (NRW): Real losses plus apparent losses plus authorized unbilled consumption. Not all non-revenue water is leakage, and authorized unbilled use can serve a public purpose.
Authorized consumption: Use permitted by the utility, whether billed or unbilled and whether metered or estimated. It includes ordinary customer use and approved operational uses.
Billed authorized consumption: Authorized water use for which the utility issues a bill. An audit volume does not establish whether every bill was collected.
Unbilled authorized consumption: Permitted use for which no bill is issued, such as approved flushing or firefighting. It belongs in the water balance even when no revenue is expected.
Water mains: The distribution pipes that carry water through the system. Main length provides context for leak exposure and for indicators expressed per mile.
Service connections: Connections between distribution mains and individual services. The audit count is not the same as population, customer accounts, or individual people.
Source meters: Meters measuring water produced by the utility or entering its supply boundary. Errors here affect the starting quantity in the balance and can shift the calculated loss volume.
Customer meters: Meters measuring use at customer services. Under-registration can reduce recorded consumption without reducing the amount actually delivered.
Water imported: Water received from another utility across the audited boundary. Purchased-water invoices and import-meter records help establish both volume and cost.
Water exported: Water delivered across the audited boundary to another utility. Exports are removed when calculating water supplied to the system under review.
MG: Million gallons. One MG equals 1,000,000 gallons, or 1,000 units of 1,000 gallons. MG is a volume; MG per day is a flow rate.
Infrastructure Leakage Index (ILI): Estimated annual real losses divided by UARL. This dimensionless ratio depends on the quality of the balance and the applicability of the reference model. It is not a universal letter grade.
Unavoidable Annual Real Losses (UARL): A modeled technical reference for leakage using system characteristics including mains, connections, service piping, and pressure. It is not a measured leak total, a legal allowance, or an economic target.
Data validity score: A weighted score from 0 to 100 describing the support for audit inputs and data practices. A score of 80 does not mean the volume is 80 percent accurate.
Variable production cost (VPC): The unit cost associated with producing or purchasing additional water and delivering it, commonly including power, treatment chemicals, and wholesale purchases. Read the calculation and contract terms before treating the audit value as cash savings.
Dollars per million gallons ($/MG): A cost per MG. Multiply a volume in MG by a value in $/MG to calculate dollars. Keep this unit separate from a retail charge per 1,000 gallons.
Customer retail unit cost ($/1,000 gallons): A retail value used to estimate the revenue associated with apparent losses. Convert MG to thousands of gallons before multiplying. It is not the production cost of leaking water.
Economic level of leakage: The leakage level at which the combined cost of leakage and the work to control it is minimized. Local supply costs, repair costs, constraints, and service needs matter.
Qualified Water Loss Auditor (QWLA): A person qualified under Georgia’s program to review and certify a water-loss audit. Certification documents review; it does not remove uncertainty from estimates.
Audit validation: Review of an audit’s inputs, documentation, methods, and data grades. Validation may lead to corrected inputs or revised estimates, which can change reported losses without a physical change in pipes.
Default estimates: Software assumptions used when system-specific evidence is unavailable. A default is not a field measurement. Identify it and seek the work needed to replace it with documented local information.
Average operating pressure (PSI): An estimate of typical pressure across the distribution system during the audit period. It is not a measurement at every property or a record of short pressure spikes. PSI means pounds per square inch.
Normalization: Expressing a volume relative to connections, mains, or time, such as gallons per connection per day. Compare normalized results alongside total volume and consistent system boundaries. A smaller denominator can raise an indicator even without a larger loss volume.
Water-loss control program: The utility’s documented investigation and improvement plan, with a baseline, goals, actions, resources, deadlines and progress measurement.
Normalized performance measures: Losses divided by connections, main length or time. These put scale in context, but changes in the denominator can move a rate even if loss volume does not change.