Water Loss Assessment in Distribution Networks: Methods, Applications and Implications in Intermittent Supply

Water utilities worldwide lose 128 billion cubic meters annually, causing annual monetary losses estimated at USD 40 billion. Most of these losses occur in developing countries (74%). This calls for a rethinking of the challenges facing water utilities in developing countries, foremost of which is the assessment of water losses in intermittent supply networks. Water loss assessment methods were originally developed in continuous supply systems, and their application in intermittently operated networks (in developing countries) is hindered by the widespread use of household water tanks and the unauthorised consumption. This study provides an extensive review of existing and new methods and (software) tools for water loss assessment. As the volume of water loss varies monthly and annually according to the amount of water supplied, this study proposes procedures to normalise the volume of water loss in order to enable water utilities to monitor and benchmark their performance in water loss management. In addition, a practical method was proposed for estimating apparent losses using data of WWTP inflows, enabling future real-time monitoring of losses in networks. The study then examines the applicability of minimum night flow analysis in the case of intermittent supply, and models the accuracy of the customer water meter under intermittent supply conditions. Finally, the study provides guidance to improve the accuracy of water loss assessment in intermittent supply networks. Accurate assessment of water loss is a prerequisite for reliable leakage modelling and minimisation, as well as planning for, and monitoring of water loss management in distribution networks.