Thakur et al. (2025) Unveiling the impact of potential evapotranspiration method selection on trends in hydrological cycle components across Europe

Identification

• Journal: Hydrology and earth system sciences
• Year: 2025
• Date: 2025-09-16
• Authors: Vishal Thakur, Yannis Markonis, Rohini Kumar, Johanna Ruth Thomson, Mijael Rodrigo Vargas Godoy, Martin Hanel, Oldřich Rakovec
• DOI: 10.5194/hess-29-4395-2025

Research Groups

• Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Prague, Czech Republic
• Department Computational Hydrosystems, UFZ-Helmholtz Centre for Environmental Research, Leipzig, Germany
• River-Coastal Science & Engineering, Tulane University, New Orleans, Louisiana, USA

Short Summary

This study evaluates the impact of selecting different potential evapotranspiration (PET) methods on trends in actual evapotranspiration (AET), runoff (Q), and total water storage (TWS) across 553 European catchments. It finds that annual and seasonal trends are variably sensitive to the PET method choice, depending on the hydrological component and catchment type, underscoring the importance of careful method selection for robust hydrological assessments.

Objective

• To assess the trends of potential evapotranspiration (PET) using 12 different methods and their influence on the trends of actual evapotranspiration (AET), runoff (Q), and total water storage (TWS) across 553 European catchments.
• To evaluate the agreement among different PET methods on the trends of AET, Q, and TWS using the data concurrence index (DCI).

Study Configuration

• Spatial Scale: 553 European catchments, ranging in size from 500 km² to 252,000 km². Data homogenized to 0.125° × 0.125° spatial resolution.
• Temporal Scale: 40 years (1980–2019) at daily and monthly time steps for hydrological components; hourly/daily for meteorological data.

Methodology and Data

• Models used: mesoscale Hydrological Model (mHM) v5.12.0
• Data sources:
  • Meteorological: Ensemble Meteorological Dataset for Planet Earth (EM-Earth) for precipitation and temperature; ERA5-Land for radiation (long- and shortwave), surface pressure, and wind components (U and V); CO2 concentration from Cheng et al. (2022).
  • Geomorphological: mHM European database (Rakovec et al., 2016) for leaf area index (LAI), soil properties (ISRIC), terrain characteristics (USGS, NGA), land cover (GlobCover by ESA), and geology (GLiM).
  • Methods: 12 PET formulations (temperature-based, radiation-based, combinational), Theil–Sen’s slope method for trend magnitude, Mann–Kendall trend test for statistical significance, Data Concurrence Index (DCI) for agreement.

Main Results

• Annual and seasonal trends of AET, Q, and TWS are variably sensitive to the choice of PET method, depending on the component and catchment category (energy-limited, mixed, water-limited).
• PET consistently shows increasing annual trends across European catchments, with the Jensen–Haise method producing the highest annual and seasonal trend magnitudes (up to 6 mm yr⁻¹), while no single method consistently yields the lowest.
• AET trends generally align with PET trends but are weaker in magnitude on an annual scale. Seasonally, only energy-limited catchments show AET trends similar to PET.
• For Q and TWS, most European catchments exhibit strong trend agreement across PET methods, but Q trends show lower sensitivity to PET methods in energy-limited and mixed catchments.
• Summer is the primary contributor to annual PET trends across all catchment categories. For AET, its influence is most notable in energy-limited and water-limited catchments.
• Statistically significant trends show general agreement for PET and AET, but decline for Q and TWS.
• Two dominant hydrological cycle patterns are observed: a water cycle intensification pattern (simultaneous increase in all components: precipitation, AET, Q, TWS) and an aridification pattern (simultaneous decline in P, Q, TWS, with an increase in AET), covering over 60% of European catchments.
• Precipitation has a stronger influence on Q and TWS than PET across all catchment categories, and on AET in water-limited catchments.

Contributions

• First comprehensive analysis of the impact of 12 different PET method selections on trends of all major hydrological cycle components (PET, AET, Q, TWS) across a large sample of 553 European catchments.
• Evaluation of agreement among PET methods using the Data Concurrence Index (DCI) for both statistically significant and all detected trends, at annual and seasonal scales.
• Identification of how PET method selection influences the classification of catchments into hydroclimatic regimes (energy-limited, mixed, water-limited).
• Highlighting the critical importance of PET method selection for robust assessments of hydrological trends and patterns, especially in the context of hydrological cycle intensification or aridification.

Funding

• Grantová Agentura České Republiky (grant no. 22-33266M)
• Česká Zemědělská Univerzita v Praze (grant no. 2023B0008)
• e-INFRA CZ project (ID:90254)
• Research Excellence in Environmental Sciences (REES) project of the Faculty of Environmental Sciences, Czech University of Life Sciences Prague

Citation

@article{Thakur2025Unveiling,
  author = {Thakur, Vishal and Markonis, Yannis and Kumar, Rohini and Thomson, Johanna Ruth and Godoy, Mijael Rodrigo Vargas and Hanel, Martin and Rakovec, Oldřich},
  title = {Unveiling the impact of potential evapotranspiration method selection on trends in hydrological cycle components across Europe},
  journal = {Hydrology and earth system sciences},
  year = {2025},
  doi = {10.5194/hess-29-4395-2025},
  url = {https://doi.org/10.5194/hess-29-4395-2025}
}