Kifle et al. (2025) Assessing the effect of climate change on extreme hydrological events in the Awash River Basin using QSWAT + and CMIP6 projections

Identification

• Journal: Theoretical and Applied Climatology
• Year: 2025
• Date: 2025-11-27
• Authors: Teshome Kifle, Gashaw Sintayehu
• DOI: 10.1007/s00704-025-05926-w

Research Groups

• Department of Water Resources and Irrigation Engineering, Institute of Technology, Woldia University, Woldia, Ethiopia
• Collage of Hydrology and Water Resources, Hohai University, Nanjing, Jiangsu Province, P.R. China

Short Summary

This study assessed the impact of climate change on hydrological extremes in the Awash River Basin using QSWAT+ and CMIP6 projections, revealing projected decreases in annual rainfall and streamflow (up to 31.4%) alongside significant temperature increases (up to 3.21 °C) by the 2050s. These changes highlight the urgent need for adaptive water resource management strategies in the region.

Objective

• To investigate trends in future climate projections and assess the effects of climate change on hydrological extremes (rainfall, temperature, streamflow) in the Awash River Basin during the 2030s and 2050s.
• To enhance estimates of climate change impacts on water availability by utilizing regionally representative CMIP6 climate models.

Study Configuration

• Spatial Scale: Awash River Basin, Ethiopia, covering an area of 111,323.12 km². Elevations range from below sea level to over 4,195 m above sea level.
• Temporal Scale:
  • Baseline period: 1985–2014 (for rainfall and streamflow), 1986–2005 (for temperature).
  • Future projection periods: Near-term (2030s: 2015–2044) and long-term (2050s: 2045–2074).
  • SWAT+ calibration period: 1986–2001.
  • SWAT+ validation period: 1996–2001.

Methodology and Data

• Models used:
  • Hydrological model: QSWAT+ (modified SWAT+ hydrologic model).
  • Climate models: Coupled Model Inter-comparison Project Phase 6 (CMIP6) Global Climate Models (GCMs), specifically ACCESS-CM2, MPI-ESM1-2-LR, MIROC6, and CNRM-CM6-1 (selected from an initial 10 GCMs).
  • Trend analysis: Sen’s Slope Test and Mann–Kendall non-parametric trend test.
  • Bias correction: CMhyd (Climate Model data for hydrologic modeling) tool.
  • Surface runoff estimation: Modified Soil Conservation Service (SCS) curve number method.
  • Potential evapotranspiration estimation: Penman-Monteith method.
  • Channel runoff routing: Muskingum method.
• Data sources:
  • Spatial data (Digital Elevation Model with 90 m resolution): USGS data archive (earthexplorer.usgs.gov).
  • Land use/cover, soil data, and gauged discharges (1985–2001): Ethiopian Ministry of Water, Irrigation, and Electricity (MoWIE).
  • Daily climatic data (rainfall, relative humidity, maximum and minimum temperatures, solar radiation, wind speed): National Meteorological Agency of Ethiopia (NMA) and Climate Forecast System Reanalysis (CFSR) (swat.tamu.edu/data/cfs).
  • CMIP6 GCM datasets (historical 1850–2014, future 2015–2100): ESGF-LLNL repository.
  • Gauged discharges (1986–2001) at Dubty gauging station: Hydrology department of the Ethiopian Ministry of Water, Irrigation, and Electricity.

Main Results

• Temperature: Annual minimum and maximum temperatures are projected to increase significantly. Maximum temperature increases up to 3.21 °C by the 2050s under the SSP585 scenario.
• Rainfall: Annual rainfall is projected to decrease across both SSP245 and SSP585 scenarios, with the most significant annual reduction of -36.7% by ACCESS-CM2 under SSP585 in the long term. While autumn and winter show decreasing trends, summer and spring exhibit slight increases.
• Streamflow: Average annual streamflow is projected to decrease, with maximum reductions of 31.4% in the 2050s. Monthly streamflow shows increases from March to May and July to September, but decreases in other months.
• Extreme Flows: Both maximum annual flow and extreme high flows (5% exceedance probability) and low flows (95% exceedance probability) are projected to decrease. The greatest decrease in maximum annual flow was -42.42% (MIROC6 under SSP245, long term).
• Potential Evapotranspiration (PET): Annual PET is projected to increase, ranging from 16.2% to 24.6% across scenarios and time horizons.
• Model Performance: The SWAT+ model demonstrated good performance with calibration metrics of Nash-Sutcliffe Efficiency (NSE) = 0.79 and Percent Bias (PBIAS) = 29.4%, and validation metrics of NSE = 0.67 and PBIAS = 33.5%.

Contributions

• Provides a comprehensive and updated assessment of climate change impacts on hydrological extremes in the Awash River Basin, a highly vulnerable region.
• Utilizes the latest CMIP6 GCMs and Shared Socioeconomic Pathways (SSP245 and SSP585) to offer more robust future climate projections.
• Employs a rigorous GCM selection and bias correction methodology to enhance the regional representativeness and reliability of climate impact assessments.
• Demonstrates the effectiveness of the QSWAT+ model in simulating complex hydrological processes under climate change scenarios in the study area.
• Offers critical insights and quantitative projections essential for informing policymakers and stakeholders in developing effective adaptive water resource management strategies for the Awash River Basin.

Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Citation

@article{Kifle2025Assessing,
  author = {Kifle, Teshome and Sintayehu, Gashaw},
  title = {Assessing the effect of climate change on extreme hydrological events in the Awash River Basin using QSWAT + and CMIP6 projections},
  journal = {Theoretical and Applied Climatology},
  year = {2025},
  doi = {10.1007/s00704-025-05926-w},
  url = {https://doi.org/10.1007/s00704-025-05926-w}
}