An Operational Groundwater-Level Forecasting System for Europe

In order to manage groundwater effectively at the pan-European scale, it is essential to treat groundwater as a shared, transboundary resource and to assess it consistently from in-situ observations. In the course of the Geological Service for Europe (GSEU) project, we compiled groundwater-level records from participating national and regional surveys. These records were subsequently harmonized into the European Groundwater Monitoring (EUGM) database. Groundwater level time series encompass diverse data sampling intervals, record lengths, continuity, and quality, frequently exhibiting non-uniform spatial coverage. The data undergoes a quality assurance process comprising the detection of stagnation periods, outlier screening, and the imputation of missing values. After the quality assurance process, the EUGM release contains 12,797 groundwater-level time series, of which 2,654 are designated as near-real-time (NRT) monitoring points, with expected monthly updates across 11 European countries.Focusing on NRT stations, we plan to develop an operational forecasting system for monthly groundwater levels using a single LSTM model trained at sites with a minimum of 20 years of observations. Meteorological predictors include precipitation, air temperature, relative humidity, and standardized precipitation indices (SPI) from ERA5-Land. The modelling period varies by site according to record length and, with the earliest possible start being 1950 in order to align with ERA5-Land availability. Results are intended for integration into the European Geological Data Infrastructure (EGDI) platform with the objective of enabling Europe-wide access, comparison, and operational use. The EUGM thereby provides a consistent observational base for cross-border assessment, modelling, and forecasting of groundwater dynamics.