Nabavi et al. (2026) Shift in streamflow seasonality and regime due to precipitation variability in a snow-influenced mountainous watershed

Identification

• Journal: Scientific Reports
• Year: 2026
• Date: 2026-09-24
• Authors: Seyedsaeid Nabavi, Ayub Mirzaei Hassanlu, Raoof Mostafazadeh
• DOI: 10.1038/s41598-026-73149-8

Research Groups

• Department of Reclamation of Arid & Mountainous Regions, Faculty of Natural Resources, University of Tehran, Karaj, Iran
• Department of Range and Watershed Management, Faculty of Natural Resources, Urmia University, Urmia, Iran
• Department of Natural Resources and Water Management Research Center, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran

Short Summary

This study analyzes the hydrological regime of the Khiav Chai River watershed from 1970 to 2022, revealing a decoupling where precipitation seasonality decreased while streamflow seasonality increased.

Objective

• To examine changes in the seasonality and trends of precipitation and streamflow in a snow-influenced mountainous watershed to determine how the hydrological regime responds to precipitation variability.

Study Configuration

• Spatial Scale: Khiav Chai River watershed, northwest Iran.
• Temporal Scale: 1970–2022.

Methodology and Data

• Models used: Innovative Trend Analysis (ITA), Pettitt change-point detection, and circular statistical analysis (including Center of Mass Timing, seasonality index, and polar vector analysis).
• Data sources: Historical precipitation and streamflow observation data.

Main Results

• Opposing Trends: Annual precipitation exhibited an upward trend (ITA slope = 0.022), whereas streamflow showed a decreasing trend (ITA slope = -0.00093).
• Change-points: Statistically significant shifts occurred in 1984 for streamflow and 1995 for precipitation.
• Seasonality Decoupling: Precipitation seasonality decreased ($\tau = -0.23, p = 0.01$), indicating a more even distribution throughout the year. Conversely, streamflow seasonality increased ($\tau = 0.34, p < 0.001$), indicating higher concentration in specific periods.
• Timing: The Center of Mass Timing was 5.09 months for precipitation and 4.45 months for streamflow.
• Snow Influence: Polar vector analysis confirmed that clustering and seasonal concentration were significantly more pronounced in streamflow than in precipitation, highlighting the mediating role of snow accumulation and melt.

Contributions

• Demonstrates that precipitation and streamflow seasonality can decouple in snow-influenced watersheds, proving that hydrological responses to climate change are not solely driven by precipitation patterns but are significantly mediated by snow dynamics.

Funding

• The authors did not receive support from any organization for the submitted work.

Citation

@article{Nabavi2026Shift,
  author = {Nabavi, Seyedsaeid and Hassanlu, Ayub Mirzaei and Mostafazadeh, Raoof},
  title = {Shift in streamflow seasonality and regime due to precipitation variability in a snow-influenced mountainous watershed},
  journal = {Scientific Reports},
  year = {2026},
  doi = {10.1038/s41598-026-73149-8},
  url = {https://doi.org/10.1038/s41598-026-73149-8}
}