Application of the Infrastructure Leakage Index (ILI) Using the Example of Rhineland-Palatinate Water Utilities

Abstract

The Rhineland-Palatinate Benchmarking Project is one of the most established benchmarking initiatives among the states of Germany. Since the survey year 2005, the majority of Rhineland-Palatinate water supply companies (WVUs) have participated in it on a triennial basis. The Infrastructure Leakage Index (ILI) has been recommended by the International Water Association (IWA) for many years as one of several indicators for assessing real water losses in drinking water supply. In the preface to DVGW W 392 (A), it is stated that this indicator will gain greater significance in Germany in the context of evaluating the tightness of water distribution networks in the future [1]. In the final report on the development of a main key figure system for German water supply [2], it is designated as an indicator for methodological testing. Based on collected experiences in its application, a decision will be made regarding its definitive inclusion in the main key figure system. Furthermore, Directive (EU) 2020/2184 (EU Drinking Water Directive) [3] and Regulation (EU) 2020/852 (Taxonomy Regulation) [4] explicitly reference the Infrastructure Leakage Index, indicating an increasing significance of this index. This article addresses methodological difficulties in the application of the Infrastructure Leakage Index using the example of Rhineland-Palatinate WVUs. Due to the numerous factors influencing the ILI, this technical article has been divided into two parts. The first part examines various factors that can influence the technically unavoidable loss volume to be determined for calculating ILI values. The second part discusses methodological or data-related challenges in the application of the ILI.