Wednesday
Comparing water losses has in the past been complicated by inconsistent use and different interpretations of terms such as ‘unaccounted-for water’, ‘non-revenue water’, ‘legitimate usage’ and ‘losses’. Therefore, from the late 1990s the International Water Association (IWA) has been promoting an internationally consistent set of terms and definitions for the components of water losses within the water balance. Figure 1.1 illustrates the IWA terminology and relationship between the terms that are being used increasingly worldwide. Reducing water losses, leakage and wastage is a water utility’s high priority when managing the water supply and demand balance. Water losses, a component of ‘non-revenue water’ (NRW), are made up of apparent and real losses and ‘unbilled authorized consumption’. Unbilled authorized consumption, essentially unbilled metered and unmetered consumption, can be managed effectively either by installing permanent meters to measure consumption or by monitoring the supplies regularly to assess demand and identify changes in demand patterns.
