Inclusion of energy externalities in the economic level of leakage (ELL) model

The Economic Level of Leakage (ELL) is the leakage level which minimizes the total of the present value cost of leakage management and the present value cost of the water lost through leakage. Reducing the leakage below the ELL would cost a water utility more than the benefits of the leak reduction. The overall aim of this research is to contribute to the reduction of carbon emissions associated with management of water leakages in water distribution networks. This study adapted an IWA methodology for the determination of an Economic Level of Leakage that incorporates energy externalities associated with active leakage detection, for a water distribution zone in the city of Zaragoza, Spain, which has no history of active leakage management. The methodology used in this research divided the leakage into four components: Reported Burst Volumes, Estimated Background Leakage, Trunk Mains and Service Reservoir Leakage and Economic Unreported Real Losses. In the case of the Economic Unreported Real Losses, the calculation requires only three system-specific parameters: Cost of Intervention (CI), Variable Cost of Lost Water (CV), and Rate of Rise of Unreported Leakage (RR). Of these parameters, the most critical in the research was the RR due to the experimental nature. The Estimated Background Leakage was calculated using the Burst and Background Estimate (BABE) method which requires field data such as the number of bursts, the average zone night pressure, length of mains, trunk-main losses, and number of billed properties that might not be available but that can be obtained by the water utility with a reasonable level of investment. According to the experience with the Water Utility in Zaragoza, the lack of a centralized depository of information in the Water Utility made the data collection process complicated for some data. It was noted that the main problem is not the lack of standardization between databases, but the lack of awareness of the information collected or considered by other teams in the water utility. This awareness can be improved by sharing the access to information between teams. Implementing a centralized information management system can solve the problem. The utility in Zaragoza estimated non-revenue water (NRW) to the tune of 21 million m3 (i.e. 34% of system input volume) in 2008 when the fieldwork was carried out. Approximately half of the NRW (about 9-12 million m3) was estimated to be physical losses in the distribution network. The model developed as part of this study show that the estimated ELL was 1,638 m3x103/yr, based on only one approach for active leakage detection (using noise loggers). It can be seen that the physical losses are between 5.5-7.3 times bigger than the ELL. This shows that investment in Active Leakage Control would provide significant economic and financial benefits, and improve the performance of the water utility. This research found that inclusion of energy externalities raised the ELL value by 0.4%, which appears insignificant. However, quantifying the emissions will be useful in future scenarios when various national legislations will make it compulsory to report on the energy emissions. Therefore, the model developed in this research can be adapted by utilities with limited data to quantify the effect of energy externalities in the water distribution systems. This has future important implications for policy and practice.