Tsypin et al. (2026) Influence of groundwater recharge projections on climate-driven subsurface warming: insights from numerical modeling

Identification

• Journal: Hydrology and earth system sciences
• Year: 2026
• Date: 2026-03-30
• Authors: Mikhail Tsypin, Viet Dung Nguyen, Mauro Cacace, Guido Blöcher, Magdalena Scheck-Wenderoth, Elco Luijendijk, Charlotte M. Krawczyk
• DOI: 10.5194/hess-30-1647-2026

Research Groups

• GFZ Helmholtz Centre for Geosciences, Potsdam, Germany
• Institute of Applied Geosciences, Technische Universität Berlin, Berlin, Germany
• Department of Earth Science, University of Bergen, Bergen, Norway

Short Summary

This study numerically models the coupled effects of rising surface temperatures and changing groundwater recharge on subsurface warming in Brandenburg, Germany, until 2100. It finds that while surface temperature is the primary driver of groundwater warming (up to 2.5 °C), groundwater flow dictates its spatial variability, and even increased winter recharge cannot counteract the overall warming trend.

Objective

• To investigate the coupled effects of rising surface temperatures and temporal trends of groundwater recharge on the subsurface thermal field from the present day to the end of the century, considering regional controls on heat advection and geological heterogeneities.

Study Configuration

• Spatial Scale: Brandenburg (northeastern Germany), covering an area of 27,600 km².
• Temporal Scale: Historical period (1950–2021) and future period (2022–2100). Results are compared between a control present period (2002–2021) and a late-century period (2081–2100).

Methodology and Data

• Models used:
  • Non-stationary Regional Weather Generator (nsRWG)
  • Mesoscale Hydrologic Model (mHM)
  • FEFLOW 8.0 (for coupled groundwater flow and heat transport)
  • PEST calibration package
• Data sources:
  • Gridded observational dataset E-OBS version 25.0e (daily precipitation, minimum, maximum, and mean near-surface air temperatures for 1950–2021)
  • ERA5 reanalysis dataset (for historical circulation patterns and regional temperatures)
  • IPCC Coupled Model Intercomparison Project Phase 6 (CMIP6) General Circulation Models (GCMs) for future projections (SSP245 and SSP585 scenarios)
  • Digital elevation model, soil properties, land use, land cover, and reservoir lithology
  • Regional geological model of Brandenburg
  • Historical groundwater level (GWL) observations
  • Groundwater temperature data (bottom-hole temperatures and corrected continuous cased-hole temperature logs)
  • Lithosphere-scale thermal model of Brandenburg (for basal heat flux)

Main Results

• Surface temperature rise is the primary driver of projected groundwater warming, reaching up to 2.5 °C by 2100 under the SSP585 scenario.
• Groundwater flow dictates the regional variability in the magnitude and affected depths of warming. Higher hydraulic gradients on topographic highs and thicker permeable Quaternary units allow the warming signal to propagate below 200 m, while groundwater discharge in river valleys limits it to less than 200 m.
• By the late century, the difference in groundwater temperatures between recharge-reduction and recharge-increase scenarios can reach 0.4 °C.
• Under the high-emissions pathway (SSP585), a 20% recharge reduction (from a mean of 75 to 60 mm a⁻¹) causes a 2–5 m water level decline, reducing the area of unconfined aquifer subjected to seasonal temperature fluctuations.
• Even a hypothetical increase in winter recharge does not suffice to counteract the groundwater warming induced by rising surface temperatures.
• Changes in advection rates are not expected to significantly affect net climate-driven heat accumulation in the subsurface due to the counterbalancing of heat gains and losses between recharge and discharge areas.
• The mean accumulated heat-in-place is projected to be 736 MJ m⁻² under SSP585, more than twice that of SSP245 (328 MJ m⁻²). Most heat accumulates in the Quaternary unit.

Contributions

• This study provides the first systematic investigation of the coupled effects of rising surface temperatures and long-term changes in groundwater recharge on the subsurface thermal field, using a comprehensive workflow integrating stochastic weather generation, distributed hydrologic modeling, and regional thermo-hydraulic groundwater modeling.
• It applies this integrated approach to a complex, low-relief, post-glacial setting in north-central Europe (Brandenburg, Germany), offering insights into how the interplay of topographic gradients and heterogeneous permeability fields controls 3-D flow patterns and heat transport.
• The research demonstrates that while advection significantly influences heat transport in the shallow subsurface, its local enhancements and buffering effects spatially compensate each other, leading to only minor impacts on the basin-wide heat budget, irrespective of the recharge trend.
• The findings highlight the critical importance of incorporating transient surface temperature and recharge boundary conditions when assessing shallow geothermal potential and temperature-dependent ecosystems under climate change.

Funding

• GFZ Helmholtz Centre for Geosciences (for Mikhail Tsypin's research and publication, and article processing charges)
• German Federal Ministry of Education and Research (projects 01LP1903E and 01LP2324E) within the ClimXtreme network (for Viet Dung Nguyen)
• Ministry of Science, Research and Culture of the State of Brandenburg (MWFK) (for high-performance computing resources)
• Project DEAL (Open Access funding)

Citation

@article{Tsypin2026Influence,
  author = {Tsypin, Mikhail and Nguyen, Viet Dung and Cacace, Mauro and Blöcher, Guido and Scheck-Wenderoth, Magdalena and Luijendijk, Elco and Krawczyk, Charlotte M.},
  title = {Influence of groundwater recharge projections on climate-driven subsurface warming: insights from numerical modeling},
  journal = {Hydrology and earth system sciences},
  year = {2026},
  doi = {10.5194/hess-30-1647-2026},
  url = {https://doi.org/10.5194/hess-30-1647-2026}
}