Deka et al. (2026) A Multi‐Model Ensemble Reveals a Diverging Hydrological Cycle in the Upper and Lower Transboundary Brahmaputra River Basin

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Identification

• Journal: International Journal of Climatology
• Year: 2026
• Date: 2026-08-11
• Authors: Priyam Deka, Manabendra Saharia, Sharad Jain, Ved Prakash, Sujay Kumar, Augusto Getirana, Suneet Bansal, Kondapalli Niranjan Kumar, V. S. Prasad, Mrutyunjay Mohapatra
• DOI: 10.1002/joc.70549

Research Groups

• Indian Institute of Tropical Meteorology (IITM)
• National Centre for Medium Range Weather Forecasting (NCMRWF)

Short Summary

This study uses a multi-model ensemble to assess the long-term trends and variability in the water budget components of the Brahmaputra basin from 1981 to 2020, revealing spatial divergence in the hydrological cycle.

Objective

• Investigate the long-term trends and variability in the water budget components of the Brahmaputra basin using a multi-model ensemble approach.

Study Configuration

• Spatial Scale: Basin-wide (covering approximately 66 million people across four countries)
• Temporal Scale: 40-year period from 1981 to 2020

Methodology and Data

• Models used: Indian Land Data Assimilation System (ILDAS) multi-model ensemble
• Data sources: Satellite, observation, reanalysis data

Main Results

• No significant long-term trend in annual basin-averaged precipitation, evapotranspiration (ET), and runoff observed.
• Spatial divergence in the hydrological cycle within the basin, with accelerating hydrologic cycle in the upper/Himalayan part and decelerating hydrological cycle in the lower/plain part.
• Decrease in winter precipitation by 5 mm per decade confined to the lower part of the basin.
• Increase in precipitation in the pre-monsoon and monsoon periods in the upper part of the basin, resulting in increasing ET and runoff.

Contributions

• Provides new insights into the complex variability of the hydrology of the Brahmaputra River basin.
• Highlights the importance of considering spatial divergence in the hydrological cycle when assessing long-term trends.

Funding

• This research was supported by the Ministry of Earth Sciences (MoES) under the National Monsoon Mission (NMM).

Citation

@article{Deka2026MultiModel,
  author = {Deka, Priyam and Saharia, Manabendra and Jain, Sharad and Prakash, Ved and Kumar, Sujay and Getirana, Augusto and Bansal, Suneet and Kumar, Kondapalli Niranjan and Prasad, V. S. and Mohapatra, Mrutyunjay},
  title = {A Multi‐Model Ensemble Reveals a Diverging Hydrological Cycle in the Upper and Lower Transboundary Brahmaputra River Basin},
  journal = {International Journal of Climatology},
  year = {2026},
  doi = {10.1002/joc.70549},
  url = {https://doi.org/10.1002/joc.70549}
}