Pimentel et al. (2025) Asymmetry in snow-water nexus in mountain areas mainly governed by meteorological seasonal changes

Identification

• Journal: Scientific Reports
• Year: 2025
• Date: 2025-11-25
• Authors: Rafael Pimentel, Claudia Notarnicola
• DOI: 10.1038/s41598-025-29597-9

Research Groups

• Fluvial Dynamics and Hydrology, Andalusian Institute for Earth System Research, University of Cordoba, Spain.
• Department of Agronomy, Unit of Excellence María de Maeztu (DAUCO), University of Córdoba, Spain.
• Institute for Earth Observation, EURAC Research, Bolzano, Italy.

Short Summary

This study analyzes 548 mountain catchments globally to quantify the nexus between snow cover and streamflow, revealing that only 5% of catchments show simultaneous significant trends in both variables. The findings highlight an asymmetric relationship where seasonal meteorological drivers, such as summer temperature increases or winter precipitation shifts, often decouple snow cover changes from annual water yield.

Objective

• To evaluate the global nexus between snow cover (area and phenology) and streamflow in mountain regions and identify the meteorological drivers (temperature and precipitation) that govern their mutual variability or lack thereof.

Study Configuration

• Spatial Scale: Global (548 selected mountain catchments with >10% snow cover area across major ranges including the Andes, Alps, and North American mountains).
• Temporal Scale: 2000–2022 (23 hydrological years).

Methodology and Data

• Models and Tools: Google Earth Engine (GEE) for satellite processing; World Hydrological Input Set-up Tool (WHIST) for catchment delineation; Mann-Kendall test for trend detection; Sen’s slope for trend magnitude estimation.
• Data sources:
  • Snow: NASA MODIS (MOD10A1.006) daily 500 m grid for Snow Cover Area (SCA), Snow Cover Duration (SCD), First Snow Day (FSD), and Last Snow Day (LSD).
  • Streamflow: Global Runoff Database (GRDC) for annual mean daily streamflow ($Q_{mean}$).
  • Meteorology/Reanalysis: ERA5-Land for temperature ($T$), total precipitation ($P$), solid precipitation ($S$), and Snow Water Equivalent (SWE).

Main Results

• Group 1 (Simultaneous Change): Found in 5% of catchments (primarily the Andes). These areas show a significant decrease in both SCA (-15.4%) and $Q_{mean}$ (-66.88 m³/s), driven by a reduction in solid precipitation. The snow season in these regions ends approximately 28 days earlier.
• Group 2 (Snow Change Only): Found in 6% of catchments (primarily the European Alps). These show significant SCA decline (-6.6%) but no significant change in $Q_{mean}$. This is attributed to summer temperature increases that affect snow presence but do not impact the spring-melt-dominated streamflow of the same year.
• Group 3 (Streamflow Change Only): Found in 10% of catchments (primarily Western North America). These show significant $Q_{mean}$ increases (+70.4 m³/s) without significant SCA trends, linked to increased winter solid precipitation and atmospheric river activity.
• General Trend: Only 21% of the studied catchments exhibited a significant trend in at least one of the two primary variables, indicating high regional variability in the snow-water nexus.

Contributions

• Provides the first global-scale assessment of snow phenology (FSD, LSD, SCD) in direct connection with observed streamflow.
• Identifies the "asymmetric behavior" of mountain catchments, demonstrating that SCA changes are not universal predictors of streamflow changes.
• Distinguishes between temperature-driven snow loss (which may not immediately impact annual flow) and precipitation-driven changes (which show a stronger coupling with water yield).

Funding

• Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033).
• European Union “NextGenerationEU”/PRTR (Project CNS2023-145125).
• Severo Ochoa and María de Maeztu Program for Centres and Units of Excellence in R&D (CEX2019-000968-M).

Citation

@article{Pimentel2025Asymmetry,
  author = {Pimentel, Rafael and Notarnicola, Claudia},
  title = {Asymmetry in snow-water nexus in mountain areas mainly governed by meteorological seasonal changes},
  journal = {Scientific Reports},
  year = {2025},
  doi = {10.1038/s41598-025-29597-9},
  url = {https://doi.org/10.1038/s41598-025-29597-9}
}

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