Application of the Infrastructure Leakage Index (ILI) as a Water Loss Indicator in Benchmarking

The Rhineland-Palatinate benchmarking is one of the most established benchmarking initiatives in Germany. Since 2005, most water utilities have participated on a three-year cycle. The Infrastructure Leakage Index (ILI) is recommended by the International Water Association (IWA) for evaluating real water losses. According to DVGW W 392 (A), the ILI is expected to gain significance in Germany. The final report on the development of the German key performance indicator system mentions the ILI as a metric for methodological testing. This article addresses the methodological challenges in applying the ILI to Rhineland-Palatinate water utilities. Due to the numerous influencing factors, the article is divided into two parts: Part 1 examines factors affecting the unavoidable annual real losses and their compensation. Part 2 discusses methodological and data-related challenges.

The first part of this technical paper discussed the application of the Infrastructure Leakage Index (ILI) as a metric for assessing real water losses under the specific conditions of water supply systems in Rhineland-Palatinate. It was noted that despite various corrections applied to the unavoidable annual real losses (UARL), many water utilities in the state achieve ILI values below 1. The second part of this paper focuses on practical challenges of applying the ILI, particularly regarding the accuracy and availability of operational data and a potential underestimation of real losses. The analysis highlights common errors in data collection and processing, revealing difficulties that can occur when calculating the ILI. The article concludes by evaluating the ILI’s suitability as an indicator for assessing water losses in benchmarking initiatives and in other contexts and compares it with other water loss metrics.

Part 1: Download now

Part 2: Download now