Analysis-ready European Groundwater Monitoring (EUGM) database

Reliable pan-European groundwater assessment has long been constrained by fragmented monitoring networks, heterogeneous data formats, and uneven quality-control practices across countries. Within the Geological Service for Europe (GSEU), the groundwater quantity working group addressed this gap by compiling groundwater level (GWL) time series from national and regional geological surveys into the European Groundwater Monitoring (EUGM) database. These GWL time series were harmonized through a standardised workflow that included quality control, resampling to monthly median values, outlier detection, artificial-shift detection, completeness filtering, and gap imputation, resulting in harmonized GWL time series at 15,760 monitoring points. The dataset is complemented by dynamic variables, including precipitation and temperature, and by static variables such as soil properties, lithology, terrain metrics, land cover, population density, and hydrological attributes. In addition, groundwater signatures and Standardised Groundwater Index (SGI) time series were derived from the imputed groundwater records to support the characterization and comparison of groundwater dynamics and anomalies across monitoring points. The dataset is further used to illustrate example applications, including long-term GWL trend analysis and SGI-based cluster classification of temporal GWL dynamics. Together, these data products provide a reproducible basis for groundwater resources assessment, modelling and forecasting across Europe.