Silva et al. (2025) A hydrological model to assess current and future freshwater availability: application to climate change impacts on hydrology in the Amazon River Basin through mid-century

Identification

• Journal: Journal of Hydrology
• Year: 2025
• Date: 2025-10-25
• Authors: Silvia R. Santos da Silva, Fekadu Moreda, Fernando Miralles‐Wilhelm, Alexandra Dias Moreira, Stephan von Borries, Félipe Cisneros, R. Muñoz-Castillo, Paula Roberts, Raphaél Payet-Burin, Silvio Pereira-Cardenal, Eveline Vasquez-Arroyo
• DOI: 10.1016/j.jhydrol.2025.134473

Research Groups

• University of Maryland Center for Environmental Science, United States of America
• RTI International, United States of America
• Amazon Cooperation Treaty Organization, Brazil
• Inter-American Development Bank, United States of America
• Danish Meteorological Institute, Denmark
• COWI A/S, Denmark
• International Finance Corporation, United States of America

Short Summary

This study developed and applied an enhanced Hydro-BID hydrological model to assess current and future freshwater availability in the Amazon River Basin (ARB) through mid-century under various climate change scenarios. The findings project a predominant decrease in freshwater availability across the ARB, with significant spatial variability and intensified impacts under high-emissions scenarios, particularly during low-water months.

Objective

• To assess the performance of the Hydro-BID model in reproducing observed streamflow regimes across the Amazon River Basin (ARB).
• To demonstrate Hydro-BID's capability as a modeling tool for assessing surface freshwater availability from basin-wide to subbasin scales within the ARB.
• To quantify the potential climate change impacts on ARB's water availability by mid-century (2031–2050) using Hydro-BID forced by the latest generation of climate models and scenarios.

Study Configuration

• Spatial Scale: Entire Amazon River Basin (ARB), covering approximately 5.9 million square kilometers, divided into 64,939 interconnected catchments with a mean area of 91 square kilometers. Analysis conducted from basin-wide to major subbasin scales.
• Temporal Scale: Historical period (1995–2014) for baseline and model calibration/validation (2000–2014). Future projection period (2015–2050), with anomalies calculated for 2031–2050. Simulations were performed at a daily time step and aggregated to monthly resolution.

Methodology and Data

• Models used: Enhanced Hydro-BID hydrological modeling system, a conceptual semi-distributed rainfall-runoff model based on the Generalized Watershed Loading Function (GWLF).
• Data sources:
  • Atmospheric forcing: Ensemble mean of five Global Climate Models (GCMs) from ISIMIP3b (GFDL-ESM4, IPSL-CM6A-LR, MRI-ESM2-0, MPI-ESM1-2-HR, UKESM1-0-LL) under SSP126 (low emissions), SSP370 (high emissions), and SSP585 (very high emissions) scenarios. Daily precipitation and near-surface air temperature at 0.5° grid resolution.
  • Hydrologic datasets: Daily streamflow measurements from 93 hydrometric gauge stations obtained from HIDROWEB (Brazilian National Water Agency - ANA) and DHIME (Colombia’s Institute of Hydrology, Meteorology and Environmental Studies - IDEAM) for calibration and validation (2000–2014).
  • Hydro-BID internal data: Analytical Hydrographic Dataset (AHD) derived from NASA SRTM/USGS digital elevation data, USGS Global Land Characterization for land cover, Harmonized World Soil Database (HWSD) for global soil data, USDA soil texture class, and hydrological soil groups.

Main Results

• Model Performance: Hydro-BID demonstrated reasonable predictive skills, with 94% of gauges showing overall volume error (OVE) within ±10%, and 96% (r) and 83% (rmod) showing satisfactory to very good correlation. The model accurately reproduced mean annual discharge (r = 0.999) and mean monthly discharge (r = 0.993) compared to observations.
• Climate Impacts on Freshwater Availability: Future projections indicate a predominant decrease in freshwater availability across the ARB, with impacts intensifying under higher emissions scenarios.
• Runoff Anomalies: Under high-emissions scenarios (SSP370 and SSP585), the ARB predominantly faces negative annual runoff anomalies of 10–20%, with more pronounced drier conditions projected for the southern and northeastern parts of the basin.
• Tributary and Subbasin Impacts: For major tributaries, annual runoff and discharge impacts range from −20% to −5% under SSP370 and SSP585. The Abacaxis, Javari, and Trombetas subbasins are projected to experience the largest reductions (between −20% and −14%), while Jurua, Madeira, Negro, Purus, Tapajos, and Xingu subbasins show non-trivial negative anomalies (11–14%).
• Flow Duration Curves (FDCs): FDCs for future scenarios shift towards a drier hydrological state, indicating a decline in the probability of exceeding any given discharge value. Reductions in streamflow are more accentuated during low-water months, with some subbasins experiencing negative anomalies of 30% or more in low flows under high-emissions scenarios.
• Basin-wide Changes: Annual runoff and streamflow for the entire ARB are projected to decrease by approximately −4% under SSP126 and by −11% under SSP370 and SSP585.

Contributions

• Development of an enhanced version of the Hydro-BID modeling system specifically optimized for large-scale domains like the Amazon River Basin.
• First application and comprehensive performance assessment of this enhanced Hydro-BID version across the entire ARB.
• Provision of new insights into the climatic effects on the hydrological regime of the entire ARB and its major subbasins, utilizing recent IPCC AR6 climate data and scenarios.
• The climate-impact simulations serve as a foundational input for a broader Water-Energy-Food (WEF) nexus modeling exercise.

Funding

• Inter-American Development Bank (IDB) award RG-T3489 (Development of a Regional Hydrological Platform and a Multi-Sector Nexus Model for the Amazon Basin).

Citation

@article{Silva2025hydrological,
  author = {Silva, Silvia R. Santos da and Moreda, Fekadu and Miralles‐Wilhelm, Fernando and Moreira, Alexandra Dias and Borries, Stephan von and Cisneros, Félipe and Muñoz-Castillo, R. and Roberts, Paula and Payet-Burin, Raphaél and Pereira-Cardenal, Silvio and Vasquez-Arroyo, Eveline},
  title = {A hydrological model to assess current and future freshwater availability: application to climate change impacts on hydrology in the Amazon River Basin through mid-century},
  journal = {Journal of Hydrology},
  year = {2025},
  doi = {10.1016/j.jhydrol.2025.134473},
  url = {https://doi.org/10.1016/j.jhydrol.2025.134473}
}