Comprehensive mapping and classification of Germany’s drinking water protection areas

Abstract Groundwater supplies up to 65% of drinking water in the European Union and approximately 70% in Germany, making it essential to preserve both its quality and quantity. However, climate change, land use pressures, and socio-economic developments increasingly threaten groundwater resources, posing significant challenges for current and future water supply. To safeguard drinking water sources, water protection areas (WPAs) are designated to mitigate contamination risks. This study introduces the first harmonized, country-wide dataset of all 11,406 designated German WPAs, integrating hydrogeological, land cover, and socio-economic characteristics, to assess groundwater vulnerability. We found these WPAs to cover the full range of the country's hydrogeological characteristics while they have higher forest cover fractions than the entire country. A cluster analysis with key characteristics classified all WPAs into 11 distinct characteristic typologies. Comparing the clusters’ groundwater chemical status as per EU Water Framework Directive mapping as an indicator of groundwater vulnerability shows that a complex interplay of hydrogeological conditions, land use patterns, and socio-economic pressures determines the differences. Our study provides a data-driven basis to support sustainable groundwater protection and drinking water resource management across Germany. It stands as exemplary for how to determine a reduced set of WPA types and situations for which to design specific measures. The results also underscore the importance of harmonized WPA designation practices to improve comparability and ensure equitable protection standards across federal states. As the current German Drinking Water Regulation operationalizes the EU Drinking Water Directive, the developed typology may also inform risk-based groundwater protection efforts in other EU Member States.