Adapting the IWA water balance to intermittent water supply and flat-rate tariffs without customer metering
The International Water Association water balance is an approach applied worldwide for determining and analysing water losses in water distribution systems (WDS) up to the point of customer metering. Thus, water losses occurring ‘before’ a customer meter are at the expenses of the water utility while water lost or wasted ‘after’ the meter is paid for by the customer. This applies to systems where customer metering is in place and/or consumption is charged according to the consumed volumes. However, many WDS in the world lack customer meters, are operated intermittently and a considerable amount of water is lost or wasted within the private property, e.g. by overflows of private tanks. The flat-rate tariff applied might not cover this amount or part of the amount. Thus, actual consumption and wastage should be separately quantified or estimated with respect to the utility's water reduction measures and the calculation of revenue water. This paper presents a water balance approach adapted to WDS which are operated intermittently, lack customer metering and charge flat-rate tariffs as well as a methodology for establishing the balance. The application is demonstrated for a district metered area of the city of Tiruvannamalai, India.