Garrote et al. (2025) From global climate models to local water stress: A framework for estimating future water availability in the Mediterranean

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2025
• Date: 2025-11-20
• Authors: Luís Garrote, Álvaro Sordo‐Ward, Paola Bianucci, Francisco Martín‐Carrasco, Ana Iglesias
• DOI: 10.1016/j.ejrh.2025.102960

Research Groups

• Department of Civil Engineering, Hydraulics, Energy and Environment, Universidad Politécnica de Madrid, Madrid, Spain
• Department of Agricultural Economics, Statistics and Business Management, Universidad Politécnica de Madrid, Madrid, Spain

Short Summary

This study developed a framework to estimate future water availability in Mediterranean basins under climate change, projecting reductions of up to 26% in annual flows and 41% in potential availability by 2100 under high-emission scenarios. It highlights the critical role of reservoirs in buffering variability and shows that increasing climate variability and population growth will exacerbate water stress in the region.

Objective

• To quantify how potential water availability evolves in Mediterranean basins under historical conditions and future climate scenarios defined by the IPCC AR6 framework, considering reservoir operations, ecological flows, and demand reliability.

Study Configuration

• Spatial Scale: River basins draining into the Mediterranean Sea (excluding the Nile), covering approximately 1.5 million square kilometres across Southern Europe, North Africa, and the Near East.
• Temporal Scale:
  • Observation period: 1980–2019
  • Historical reference period: 1975–2014
  • Near-future period: 2020–2059
  • Distant-future period: 2060–2099

Methodology and Data

• Models used:
  • Global Hydrological Models: H08, CWatM (from ISIMIP3b)
  • Water Allocation Model: WAAPA (Water Availability and Adaptation Policy Analysis)
  • Validation Models: SIMPA (for Spanish basins), BIGBANG (for Italian basins)
• Data sources:
  • Climate Scenarios: Inter-Sectoral Impact Model Intercomparison Project (ISIMIP3b) using five Global Climate Models (GCMs): GFDL-ESM, MRI-ESM, IPSL-ESM, MPI-ESM, UKESM.
  • Observed Climate Data: GSWP3 (Global Soil Wetness Project Phase 3) for obsclim scenario.
  • Topographic/Hydrological: HydroSheds (3-arcsecond resolution).
  • Dams/Reservoirs: World Register of Dams (WRD), Global Reservoir and Dam Database (GRanD), GlObal geOreferenced Database of Dams (GOODD).
  • Population: Gridded Population of the World, Version 4 (GPWv4) from GRUMP (2.5 arc-minutes resolution) for 2020; Global One-Eighth Degree Population Base Year and Projection Grids Based on the SSPs, v1.01 (7.5 arc-minutes resolution) for future SSPs (SSP1, SSP3, SSP5).
  • Irrigated Area: Global Map of Irrigated Areas (GMIA) from FAO’s AQUASTAT (5 arc-minutes resolution).
  • Validation Data: Monthly discharge data from Global Runoff Data Centre (GRDC) for H08/CWatM calibration; outputs from SIMPA and BIGBANG models.

Main Results

• Mean annual streamflow is projected to decrease by up to 26% under the SSP5–8.5 scenario for the 2060–2099 period.
• Potential water availability is projected to decrease by up to 41% under the SSP5–8.5 scenario for the 2060–2099 period.
• Reservoirs currently provide 53% of the potential water availability, significantly buffering seasonal and interannual variability.
• Interannual hydrological variability is projected to increase by up to 31% in the most adverse scenarios, further compromising water supply reliability.
• Under the most adverse scenario (SSP3–7.0, 2060–2099), the population experiencing water scarcity (<1700 m³/person/year) is projected to increase from 52% to 73% of the total regional population.
• The number of basins with absolute scarcity (<500 m³/person/year) is projected to increase from 53 (14%) to 81 (22%) under SSP3–7.0 (2060–2099).
• The most critical decline in per capita availability (to 223 m³/person/year by 2060–2099) occurs under SSP3–7.0, driven by a combination of climate impacts and a 31% population increase.

Contributions

• Provides an integrated, spatially explicit framework for estimating potential water availability in Mediterranean basins under climate change, combining global hydrological models with a water allocation model (WAAPA).
• Quantifies the combined impact of climate-driven hydrological changes and reservoir management on water availability, moving beyond purely climatological interpretations.
• Highlights the critical role of existing reservoir infrastructure in buffering climate variability and sustaining water supply, quantifying its contribution (53% of current potential availability).
• Identifies spatial hotspots of future water scarcity and increased vulnerability due to climate change, population growth, and hydrological variability.
• Offers actionable information for basin-scale adaptation strategies and integrated water resources management in the Mediterranean region.

Funding

• AG-WaMED project
• Partnership for Research and Innovation in the Mediterranean Area Programme (PRIMA), an Art 185 initiative supported and funded under Horizon 2020.
• Grant Agreements: Italy: 391 of 20/10/2022, Egypt: 45878, Tunisia: 0005874–004–18–2022–3, Greece: ΓΓР21–0474657, Spain: PCI2022–132929.

Citation

@article{Garrote2025From,
  author = {Garrote, Luís and Sordo‐Ward, Álvaro and Bianucci, Paola and Martín‐Carrasco, Francisco and Iglesias, Ana},
  title = {From global climate models to local water stress: A framework for estimating future water availability in the Mediterranean},
  journal = {Journal of Hydrology Regional Studies},
  year = {2025},
  doi = {10.1016/j.ejrh.2025.102960},
  url = {https://doi.org/10.1016/j.ejrh.2025.102960}
}