Water losses in the public water supply system: Harmonization of reporting under the drinking water directive

Water losses in public water supply systems represent a significant challenge for the sustainable management of water resources in the EU. The Drinking Water Directive (DWD, 2020/2184) obliges Member States to assess the levels of losses in distribution networks and report to the European Commission by January 2026. Different reporting methodologies make data comparability difficult, which requires harmonisation. EurEau proposes a volumetric index (m³/km/year) for standardised reporting, with a contextual annex for data interpretation. The paper analyses the implementation challenges, including technical constraints and local conditions, and highlights the Italian experience in monitoring losses.