The project “Study of the Water Quality History in Small Municipalities of the Barcelona Province” (HISQUABAR) is a collaboration between the Diputació de Barcelona and the Catalan Institute for Water Research (ICRA). Its aim is to analyze and describe the evolution of drinking water quality in around 80 municipalities with fewer than 5,000 inhabitants in the Barcelona province, based on self-monitoring data available from 2015 to 2023. The study includes a statistical and geographic analysis of the main water parameters, such as nitrates, sulfates, fluorides, arsenic, lead, chlorates, and microbiological indicators, to identify non-compliances and temporal or spatial trends. The results will be included in the interactive map viewer where the Diputació de Barcelona publishes its data. The project, led by Josep Pueyo-Ros with the participation of an interdisciplinary ICRA team, will be carried out between June 2025 and May 2026, including a final presentation at the “Water and Health” Conference organized by the Diputació de Barcelona.