Identificazione del campione ottimale di consumi per la stima del bilancio idrico in un ATO: il caso di Siracusa

This paper describes the application of sampling theory’s principles to the assessment of water consumptions to draw up water balances of distribution networks (or networks’ districts) of municipalities in an ATO (optimal water service territorial unit), in order to estimate water losses and single out the right intervention priorities. The basic idea is to perform a limited number of measurements to estimate the total water consumptions of connections. Stratified sampling and simple random sampling techniques are compared from the point of view of required sample size to get estimations with given precision and confidence level. An early application of this method to a hypothetical network district, built starting from a cluster of real connections, showed how the stratified sampling allows a remarkable reduction of sampling fraction, which is mainly affected by estimation precision and assumes reasonable values even for high precisions. On the basis of this first application it has been decided to adopt this methodology within the knowledge project of Syracuse’s ATO. The first promising results have been corroborated by a later application to the residential uses of small Sicilian municipality.