Dadparvar et al. (2025) Assessment of drought trends in the Aras River Basin: Spatiotemporal changes and implications for transboundary water management

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2025
• Date: 2025-09-10
• Authors: Shabnam Dadparvar, Ameneh Mianabadi, Hojjat Mianabadi, Saeed Nastarani Amoghin, Sedigheh Anvari
• DOI: 10.1016/j.ejrh.2025.102761

Research Groups

• Tianshui Normal University, Gansu, China
• Department of Ecology, Institute of Science and High Technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, Iran
• Department of Water Engineering and Management, Tarbiat Modares University, Tehran, Iran
• Department of Irrigation & Reclamation Engineering, Faculty of Agricultural Engineering & Technology, College of Agriculture & Natural Resources, University of Tehran, Karaj, Iran

Short Summary

This study assesses spatiotemporal drought trends in the transboundary Aras River Basin from 1981 to 2022 using satellite precipitation and evaporation data, revealing significant drought intensification in the southern regions driven primarily by increased evaporative demand rather than precipitation deficits, with critical implications for transboundary water management.

Objective

• To evaluate spatiotemporal changes in drought characteristics (1981–2022) in the transboundary Aras River Basin using the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI).
• To demonstrate the usability of global evapotranspiration databases and satellite precipitation products for drought monitoring in transboundary river basins with limited ground-based data sharing.
• To identify climatic shifts to inform adaptive management strategies and foster transboundary cooperation among riparian states.

Study Configuration

• Spatial Scale: Transboundary Aras River Basin (ARB), approximately 100,000 km², shared by Türkiye (24.5%), Iran (39.3%), Armenia (23.2%), and Azerbaijan (12.9%).
• Temporal Scale: 42 years, from 1981 to 2022. Drought indices were calculated for 1, 3, 6, 9, 12, 18, and 24-month timescales.

Methodology and Data

• Models used: Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Mann-Kendall trend test, Sen’s slope estimator, Budyko framework.
• Data sources:
  • Satellite Precipitation Products (validated against rain gauges):
    • CHIRPS (Climate Hazards Group InfraRed Precipitation with Station data) at 0.05°×0.05° and 0.25°×0.25° resolution (1981–2022).
    • MSWEP (Multi-Source Weighted-Ensemble Precipitation) at 0.1°×0.1° spatial resolution (1981–2022).
    • PERSIANN-CDR (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record) at 0.25°×0.25° resolution (1983–2022).
    • PERSIANN-CCS-CDR (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Cloud Classification System-Climate Data Record) at 0.04°×0.04° resolution (1983–2022).
  • Satellite Evaporation Data:
    • GLEAM v3.8 (Global Land Evaporation Amsterdam Model) for monthly potential and actual evaporation at 0.25°×0.25° resolution (1981–2022).
  • Observation Data: Precipitation data from 18 rain gauges in the Iranian part of the basin (1981–2022) for satellite product validation.

Main Results

• CHIRPS at 0.25°×0.25° resolution outperformed other satellite precipitation products, showing R² ≥ 0.9 and RMSE ≈ 10 mm/month against rain gauge data.
• Significant declines (at 95–99% confidence interval) in both SPI and SPEI were observed in the southeastern and southwestern parts of the basin (mostly in Iran) across all time scales.
• SPEI indicated more pronounced drought intensification compared to SPI, emphasizing the critical role of potential evaporation.
• The southeastern basin experienced significantly increasing evaporative ratio (E/P) and aridity index (Ep/P) at a 95% confidence interval (ZMK > 1.96), coupled with stable precipitation and rising actual/potential evaporation.
• The southern portion of the basin has faced heightened exposure to arid conditions over the 42-year period, primarily driven by evaporative demand rather than precipitation deficits.
• Annual precipitation showed increasing trends, significant in Azerbaijan (ZMK=1.99) and Armenia (ZMK=1.71), but not significant in Iran (ZMK=0.33) and Türkiye (ZMK=1.60).
• Actual and potential evaporation exhibited significant upward trends in all countries and the ARB (ZMK > 1.96), except for actual evaporation in Iran (insignificant positive trend, ZMK=1.58).
• The evaporative ratio decreased in Türkiye, Azerbaijan, and Armenia, but increased in Iran (ZMK=0.69). The aridity index increased in Iran (ZMK=0.43) and Türkiye (ZMK=0.22), while decreasing in Azerbaijan and Armenia.

Contributions

• Provides a comprehensive spatiotemporal assessment of drought characteristics across the entire transboundary Aras River Basin, addressing a gap in previous studies that often focused on sub-regions.
• Demonstrates the effective usability and validation of global satellite precipitation and evapotranspiration products (CHIRPS, GLEAM) for robust drought monitoring in data-scarce transboundary river basins, overcoming limitations of ground-based data sharing.
• Offers new hydrological insights for the region, particularly highlighting the increasing role of evaporative demand in driving drought intensification in the southern parts of the basin.
• Generates evidence-based climatic trends that can inform adaptive water management strategies and foster diplomatic dialogue and cooperation among riparian states (Türkiye, Iran, Armenia, Azerbaijan) amidst existing water disputes.

Funding

Not explicitly mentioned in the paper.

Citation

@article{Dadparvar2025Assessment,
  author = {Dadparvar, Shabnam and Mianabadi, Ameneh and Mianabadi, Hojjat and Amoghin, Saeed Nastarani and Anvari, Sedigheh},
  title = {Assessment of drought trends in the Aras River Basin: Spatiotemporal changes and implications for transboundary water management},
  journal = {Journal of Hydrology Regional Studies},
  year = {2025},
  doi = {10.1016/j.ejrh.2025.102761},
  url = {https://doi.org/10.1016/j.ejrh.2025.102761}
}