Meskelu et al. (2025) Assessment of climate change impacts on crop and irrigation water demand in the Awash River basin of Ethiopia using CMIP6 models

Identification

• Journal: Discover Water
• Year: 2025
• Date: 2025-11-27
• Authors: Elias Meskelu, Mekonen Ayana, Dereje Birhanu
• DOI: 10.1007/s43832-025-00307-w

Research Groups

• Adama Science and Technology University, Adama, Ethiopia
• Wondo Genet Agricultural Research Center, Wondo Genet, Ethiopia

Short Summary

This study assesses climate change impacts on crop and irrigation water demand in the Awash River Basin using bias-corrected CMIP6 models, projecting increased water demands for most crops, except wheat, which experienced reductions, indicating growing pressure on water resources.

Objective

• To quantitatively assess the impacts of climate change on crop and irrigation water demand for major irrigated crops in the Awash River Basin using bias-corrected ensemble CMIP6 projections under different socioeconomic scenarios (SSP2-4.5 and SSP5-8.5).

Study Configuration

• Spatial Scale: Awash River Basin, Ethiopia (114,123 km² area, between 7°52’ to 12°08’ N latitude and 37°56’ to 43°17’ E longitude, with an elevation range of 210 to 4190 m above mean sea level).
• Temporal Scale:
  • Baseline/Historical: 2000–2014
  • Future Projections:
    • Short-term: 2030s (2021–2045)
    • Medium-term: 2050s (2046–2070)
    • Long-term: 2080s (2071–2095)

Methodology and Data

• Models used:
  • Coupled Model Intercomparison Project Phase 6 (CMIP6) General Circulation Models (GCMs): ACCESS-CM2, BCC-CSM2-MR, CanESM5, EC-Earth3, GFDL-CM4, INM-CM4-8, IPSL-CM6A-LR, MIROC6, MPI-ESM1-2-LR, MRI-ESM2-0.
  • CropWat 8.0 software (for reference evapotranspiration (ETo) and crop water requirement (CWR) estimation using FAO 56-Penman–Monteith model).
  • Locally calibrated Hargreaves-Samani model (for ETo estimation in data-scarce areas).
  • CMhyd (Climate Model data for hydrologic modeling) statistical tool (for bias correction and data extraction).
  • 'ie2misc' R package (for model performance evaluation using statistical indices).
• Data sources:
  • Observed climate data (2000–2014) for 18 stations from the Ethiopian Meteorological Institute (EMI).
  • Future projected climate data under Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5) from CMIP6 GCMs via the Copernicus Climate Data Store (CDS).
  • Crop coefficient (Kc) and growth duration for selected crops adopted from the FAO-56 report and a local study for tomato.

Main Results

• Bias Correction: Linear scaling was most effective for precipitation and minimum temperature, while variance scaling and distribution mapping were favored for maximum temperature. Ensemble CMIP6 models significantly improved climate variable simulations compared to individual models.
• Temperature Projections: Both maximum and minimum temperatures showed increasing trends across all stations and scenarios.
  • Maximum temperature increased by 0.5 °C (SSP2-4.5) to 0.6 °C (SSP5-8.5) in the 2030s, and by 1.6 °C (SSP2-4.5) to 2.8 °C (SSP5-8.5) in the 2080s, relative to baseline.
  • Minimum temperature increased by 0.8 °C (SSP2-4.5) to 1.0 °C (SSP5-8.5) in the 2030s, and by 2.0 °C (SSP2-4.5) to 3.6 °C (SSP5-8.5) in the 2080s, relative to baseline.
  • Highest temperature increases were observed in the lower and middle parts of the basin.
• Precipitation Projections: Exhibited spatial heterogeneity, with a general increase in most stations, particularly in the 2080s under SSP5-8.5, but decreases were observed in a few stations (e.g., Abomsa, Awash7Kilo, Woliso in 2030s under SSP2; Kulumsa in 2030s/2050s under SSP5). Rainfall increased by up to 175.0% in dryland areas (Dubti, 2080s, SSP5).
• Reference Evapotranspiration (ETo): Generally increased, ranging from a 2.1% decrease to a 22.6% increase. Average ETo across stations increased by 4.7% (short-term), 7.6% (medium-term), and 10.3% (long-term).
• Crop and Irrigation Water Demand (CWD & IWD):
  • Wheat (upper basin): CWR declined by 3.7% to 5.0%; IWD decreased by 5.7% to 15.6% due to increased effective precipitation and slightly cooler temperatures during its growing season.
  • Maize (upper basin): CWR increased by 7.4% to 11.9%; IWD rose by 3.9% to 9.0%, with a slight reduction (-2.3%) in the 2080s under SSP5 due to increased effective precipitation.
  • Tomato (middle basin): CWR increased by 3.4% to 15.7%; IWD rose by 2.2% to 4.8%.
  • Onion (middle basin): CWR increased by 6.1% to 13.3%; IWD rose by 3.0% to 9.8%, with a decrease (-4.6%) in the 2080s under SSP5 due to significant effective precipitation.
  • Tropical Fruits (middle basin): CWR increased by 1.7% to 7.6%. IWD increased by 1.4% to 2.2% under SSP2, but slightly decreased (0.1% to 2.1%) under SSP5 due to substantial increases in annual effective precipitation.
  • Sugarcane (lower basin): CWR rose by 1.8% to 11.6%; IWD increased by up to 3.8%, with a minor decrease (-0.6%) in the 2030s under SSP5 due to substantial effective precipitation.
• Overall, irrigation water demand is projected to fluctuate between a 4.6% decrease and a 9.0% increase under different climate change scenarios, indicating growing pressure on water resources in the basin.

Contributions

• Provides a comprehensive and more reliable assessment of crop and irrigation water demand in the Awash River Basin using bias-corrected CMIP6 ensemble projections, improving upon previous CMIP5-based analyses.
• Fills a critical knowledge gap for climate-resilient agriculture and water management policies in Ethiopia by focusing on crop and irrigation water demand under future climate scenarios, unlike previous CMIP6 studies that primarily evaluated climate variable trends.
• Offers essential evidence to guide agricultural policies and practices towards climate-resilient irrigation planning, optimal crop selection, and equitable water allocation strategies.
• Highlights the necessity for adaptive irrigation strategies, including precision agriculture, water-saving technologies, crop calendar adjustments, and water storage infrastructure, to ensure sustainable water management.

Funding

No specific project or program funding was available for this study. The first author's Ph.D. study was sponsored by the Ethiopian Institute of Agricultural Research (EIAR).

Citation

@article{Meskelu2025Assessment,
  author = {Meskelu, Elias and Ayana, Mekonen and Birhanu, Dereje},
  title = {Assessment of climate change impacts on crop and irrigation water demand in the Awash River basin of Ethiopia using CMIP6 models},
  journal = {Discover Water},
  year = {2025},
  doi = {10.1007/s43832-025-00307-w},
  url = {https://doi.org/10.1007/s43832-025-00307-w}
}