Boisier et al. (2025) Increasing water stress in Chile revealed by novel datasets of water availability, land use and water use

Identification

• Journal: Hydrology and earth system sciences
• Year: 2025
• Date: 2025-10-15
• Authors: Juan Pablo Boisier, Camila Álvarez-Garretón, Rodrigo Marinao, Mauricio Galleguillos
• DOI: 10.5194/hess-29-5185-2025

Research Groups

• Center for Climate and Resilience Research (CR2, FONDAP 1523A0002), Santiago, Chile
• Department of Geophysics, Universidad de Chile, Santiago, Chile
• Department of Civil Engineering, Universidad De La Frontera, Temuco, Chile
• Faculty of Engineering and Science, Universidad Adolfo Ibáñez, Santiago, Chile

Short Summary

This study evaluates past, present, and future water stress in Chile using novel, national-scale datasets of water availability, land use, and water use. It reveals a steady increase in water stress in central Chile, primarily driven by rising water consumption and reduced availability, projecting permanent megadrought-like conditions and extreme water stress in many basins under adverse climate scenarios.

Objective

• How has water stress changed over the past six decades in Chile, according to the water use-to-availability ratio?
• How have trends in climate and water use influenced changes in water stress?
• What can be expected under future climate scenarios?

Study Configuration

• Spatial Scale: Continental Chile, covering all major basins, with climate data on a 0.05° latitude–longitude grid and land use/cover data on a 0.01° latitude–longitude grid.
• Temporal Scale: Historical analysis from 1950/1960 to 2020, and future projections extending to 2100, with a focus on the mid-21st century (2035–2065).

Methodology and Data

• Models used:
  • Water Stress Index (WSI) calculation (ratio of total consumptive water use to near-natural water availability).
  • Simplified "bucket" evapotranspiration (ET) scheme for naturalized ET (ETN) and land-use-driven ET changes (ΔETLU).
  • Quantile Delta Mapping (QDM) for bias correction of climate model outputs.
  • Hargreaves-Samani (HS) formula for potential evapotranspiration (ET0) estimation, with Penman-Monteith and wind corrections.
  • Partial derivative decomposition for attributing WSI changes to water availability and water use.
• Data sources:
  • Novel datasets developed:
    • CR2MET (v2.5): Daily precipitation and temperature for continental Chile (1960–present, 0.05° lat–lon grid).
    • CR2LUC (v1.0): Land use and land cover reconstruction for continental Chile (1950–2020, yearly, 0.01° lat–lon grid).
    • CR2WU (v1.0): Consumptive and non-consumptive water use reconstruction for continental Chile (1960–2020, yearly, communal, sectoral).
  • External data:
    • ERA5 reanalysis (ECMWF) for atmospheric variables.
    • MODIS satellite sensor for land-surface temperature.
    • CMIP6 Earth System Models (17 ESMs) for climate change projections (SSP1-2.6 and SSP3-7.0 scenarios).
    • Weather Research and Forecasting (WRF) model simulations for wind speed data.
    • National inventories and censuses (e.g., Agricultural and Livestock Censuses, ODEPA, CIREN-ODEPA, SAG, CONAF).
    • Landsat-based land cover datasets (Zhao et al., 2016; Chen et al., 2015).
    • National Inventory of Watersheds (BNA) from the Dirección General de Aguas (DGA).
    • CAMELS-CL dataset for observed river streamflow.
    • PROBA-V LAI satellite dataset (Copernicus Global Land Service) for Leaf Area Index.
    • CLSoilMaps for gridded physical and hydraulic soil properties.
    • World Population Prospects (UN, 2024).

Main Results

• During the 2010–2020 megadrought, most basins in semi-arid central Chile experienced high to extreme water stress (WSI > 40% and WSI > 70%), primarily due to reduced water availability, exacerbated by high water demand.
• Over the past six decades (1960–2020), water stress in central Chile has steadily increased, leading to sustained high water stress levels (WSI > 40% on average for 1990–2020) in several basins from Santiago northward. This increase is mainly attributed to rising water consumption (doubled since the 1960s, largely from agricultural and forestry expansion) and, to a lesser extent, to reduced surface water availability.
• Under an adverse climate scenario (SSP3-7.0), megadrought-like conditions (projected 30% precipitation drop) could become permanent by the end of the 21st century, resulting in persistently high to extreme water stress in most central Chilean basins by mid-century (2035–2065).
• Total water use in Chile for 2010–2020 is estimated at approximately 100 cubic kilometers per year (km³/yr), with consumptive use around 11.5 km³/yr (365 cubic meters per second), of which nearly three-quarters are attributed to the Land Use, Land-Use Change, and Forestry (LULUCF) sector, particularly irrigated agriculture (~9 km³/yr or 285 cubic meters per second).
• The Aconcagua River basin, an example of extreme water stress, saw its 5-year mean WSI exceed 100% during 2010–2020, indicating water use surpassing available surface water and leading to unsustainable groundwater exploitation.

Contributions

• Development of novel, national-scale datasets (CR2MET, CR2LUC, CR2WU) for water availability, land use, and water use, extending back to the mid-20th century, which address critical information gaps for Chile.
• Comprehensive evaluation of Chile's current, historical, and future water stress conditions at the basin scale, providing a detailed understanding of regional disparities.
• Quantification of the relative contributions of climate variability (water availability) and water use (demand) to changes in water stress over different time periods, offering insights into the drivers of water scarcity.
• Demonstration of the Water Stress Index (WSI) as a valuable metric for establishing quantifiable water security goals and evaluating adaptation pathways, such as reducing water use or increasing alternative water sources.
• The developed methodology is transferable and applicable to other regions facing similar data challenges and water security issues.

Funding

• Center for Climate and Resilience Research (CR2, ANID/FONDAP/1523A0002)
• ANID/FSEQ210001
• FONDECYT/11190952
• FONDECYT/11240924

Citation

@article{Boisier2025Increasing,
  author = {Boisier, Juan Pablo and Álvarez-Garretón, Camila and Marinao, Rodrigo and Galleguillos, Mauricio},
  title = {Increasing water stress in Chile revealed by novel datasets of water availability, land use and water use},
  journal = {Hydrology and earth system sciences},
  year = {2025},
  doi = {10.5194/hess-29-5185-2025},
  url = {https://doi.org/10.5194/hess-29-5185-2025}
}