Regional-scale assessment of groundwater recharge and the water balance for Austria

The study area covers Austria (83 900 km 2 ) and neighboring regions with transboundary river basins. Knowledge of regional groundwater recharge patterns is essential for sustainable water resource management. Currently, Austria lacks fully spatially distributed groundwater recharge maps. The study’s aim was to develop a nationwide hydrological model that predicts groundwater recharge and the water balance components runoff, and evapotranspiration. We implemented the rainfall-runoff model COSERO with a 1 km 2 spatial and monthly temporal resolution. In model calibration, four objective functions were evaluated to determine the most suitable one for our modeling purpose. Additionally, a two-stage calibration procedure was integrated to capture both water balance dynamics and low-flow characteristics. Model results were verified against independent studies. This study provides the first Austria-wide, fully spatially distributed groundwater recharge map for the World Meteorological Organization (WMO) reference period 1991–2020, along with updated water balance maps. We set up a consistent model framework, serving as a valuable resource for future climate change impact assessments. The model simulations yielded a long-term average groundwater recharge rate in the magnitude of 373 mm year −1 , 650 mm year −1 runoff, and 538 mm year −1 actual evapotranspiration. • Austria-wide hydrological model with 1 km 2 spatial and monthly temporal resolution. • Estimation of Austria-wide groundwater recharge rates and water balance components. • Identification of limitations and uncertainties in model setup and results.