Sustainable groundwater use depends on reliable estimates of groundwater recharge—a critical but difficult-to-quantify flux. Before water reaches the aquifer, surface inputs, vegetation, and vadose zone processes alter both its quantity and timing. Climate and land use changes, along with extreme events such as droughts and intense rainfall, further complicate the spatial and temporal dynamics of the recharge. Now more than ever, refining our understanding of recharge is critical to informing decisions and managing groundwater sustainably.
This session offers a platform to exchange concepts, expertise, and methods related to groundwater recharge estimation across disciplines and application contexts.
We invite contributions focusing on the estimation of groundwater recharge across multiple temporal and spatial scales, including studies that compare or combine different methods. Estimation approaches may be based on:

• Field-based measurements from various compartments of the hydrological cycle:
- Land surface water balance components
- Vadose zone measurements (e.g. soil moisture)
- Groundwater heads (water table fluctuations)
- Discharge measurements (baseflow separation)
- Environmental tracers for recharge estimation and model calibration (e.g., stable isotopes, radioisotopes, dissolved gases)
- Including suggestions for improved monitoring concepts

• Model-based approaches (local to global scale), such as:
- Water balance models
- Land surface models
- Physically-based vadose zone or groundwater models
- Hybrid or machine learning-supported methods
- Groundwater time-series models

• Upscaling strategies from point-scale to landscape-scale assessments

• Varying temporal scales from short-term recharge quantification to long-term recharge trends (past or future scenarios)

We welcome studies addressing recharge estimation for various purposes, including (but not limited to) agricultural water management and irrigation, forest management and ecosystem transition, groundwater resource planning, and sustainable management.