Salwey et al. (2026) Global-scale meteorological-to-groundwater drought propagation and the drivers and patterns of multi-year groundwater drought

Identification

• Journal: Earth System Dynamics
• Year: 2026
• Date: 2026-11-03
• Authors: Saskia Salwey, Sandra Margrit Hauswirth, Denise Ruijsch, Barry van Jaarsveld, Jonna van Mourik, Niko Wanders
• DOI: 10.5194/esd-17-1609-2026

Research Groups

• Department of Physical Geography, Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands

Short Summary

This study investigates global patterns and drivers of multi-year groundwater droughts using a hyper-resolution dataset (1960-2019), revealing that 35% of global groundwater grid cells experience multi-year droughts, predominantly extended by subsurface processes. The research defines three global groundwater response types to understand the interplay between meteorological and groundwater drought duration.

Objective

• To investigate the global patterns and drivers of groundwater drought from 1960–2019, with a specific focus on multi-year events.
• To characterize the propagation of meteorological drought (represented by SPEI-12) to groundwater drought, evaluating how and to what extent the subsurface modulates the meteorological drought signal.
• To define global groundwater response types to provide a framework for understanding the processes and geophysical drivers of normal versus multi-year groundwater droughts.

Study Configuration

• Spatial Scale: Global-scale, with groundwater data at approximately 1 km resolution. Recharge data at 5 arcmin (approximately 10 km at the equator). Meteorological drought index (SPEI-12) at 0.5° spatial resolution.
• Temporal Scale: 1960–2019 (60 years) for groundwater simulations. Monthly time steps for groundwater heads and water table depths. GRACE data from April 2002 to December 2019. IGRAC observational data with more than 10 years of continuous data between 1960 and 2019.

Methodology and Data

• Models used:
  • GLOBGM v1.1: A two-layer transient MODFLOW-based global groundwater model.
  • PCR-GLOBWB2: A global hydrological model used to derive inputs (local runoff, groundwater abstraction, groundwater recharge) for GLOBGM.
• Data sources:
  • GLOBGM modelled groundwater data (hyper-resolution, approximately 1 km).
  • NASA's Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) mascon gridded data (JPL solution, release 06.1 v3) for validation.
  • International Groundwater Resources Assessment Center (IGRAC) database for point observational groundwater data (validation).
  • W5E5 reanalysis data for calculating the 12-month averaged Standardized Precipitation-Evapotranspiration Index (SPEI-12).

Main Results

• 35% of global groundwater grid cells exhibit an average groundwater drought duration classified as multi-year (lasting 12 months or more).
• In 83% of these multi-year groundwater drought locations, the subsurface extends the meteorological drought signal, while in the remaining 17%, groundwater drought duration is primarily driven by meteorological anomalies.
• Approximately 49% of global groundwater cells have average drought durations shorter than the corresponding meteorological drought, and 51% exhibit longer groundwater droughts.
• The mean global groundwater drought duration is 20.4 months, with a median of 6.8 months, significantly skewed towards longer events compared to SPEI-12 droughts (mean 6.7 months, median 6.3 months).
• Three groundwater response types were identified:
  • Meteo = GW (19% of global data): Groundwater drought duration is indistinguishable from meteorological drought duration. 32% of these locations (6% of global data) have multi-year average groundwater droughts.
  • Meteo < GW (38% of global data): Groundwater droughts are, on average, longer than meteorological droughts. 76% of these locations (29% of global data) have multi-year average groundwater droughts. For 69% of these multi-year groundwater droughts, the saturated zone processes amplify a normal recharge drought into a multi-year groundwater drought.
  • Meteo > GW (43% of global data): Groundwater droughts are, on average, shorter than meteorological droughts, with almost no multi-year groundwater droughts observed.
• The global mean anomaly correlation between SPEI-12 and simulated groundwater is 0.36 (median 0.42), with 81.3% of grid cells showing a statistically significant correlation at lag 0.
• Longer groundwater lags (delay in response to meteorology) are more common in the Meteo < GW type (56% of data with lag > 1 month) and are associated with deeper groundwater and lower anomaly correlations.

Contributions

• This is the first global-scale analysis to use hyper-resolution data (approximately 1 km) specifically focusing on the drivers and patterns of multi-year groundwater drought.
• It addresses a significant gap in global drought propagation analysis by incorporating comprehensive groundwater data, which was previously limited by coarse resolution or sparse observations.
• The study quantifies the substantial role of subsurface geophysical properties in modulating meteorological droughts into multi-year groundwater droughts, showing that 35% of global groundwater cells experience multi-year droughts despite less than 2% having multi-year meteorological droughts.
• It provides a novel typology of global groundwater responsiveness, offering a baseline framework for understanding current and future vulnerability to multi-year droughts and informing drought mitigation strategies.
• The use of hyper-resolution data uniquely captures finer-scale interactions between river systems and groundwater, providing actionable insights into spatial patterns of global drought propagation for water scarcity risk management and prediction.

Funding

• European Research Council, HORIZON EUROPE European Research Council (grant nos. 101075354 and 101019185)
• Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Exacte en Natuurwetenschappen (grant no. VI.Vidi.223.009)

Citation

@article{Salwey2026Globalscale,
  author = {Salwey, Saskia and Hauswirth, Sandra Margrit and Ruijsch, Denise and Jaarsveld, Barry van and Mourik, Jonna van and Wanders, Niko},
  title = {Global-scale meteorological-to-groundwater drought propagation and the drivers and patterns of multi-year groundwater drought},
  journal = {Earth System Dynamics},
  year = {2026},
  doi = {10.5194/esd-17-1609-2026},
  url = {https://doi.org/10.5194/esd-17-1609-2026}
}