Yoshe (2026) Characterization of Drought Severity Using GRACE and TerraClimate Dataset in the Rift Valley Basin, Ethiopia

Identification

• Journal: Advances in Environmental and Engineering Research
• Year: 2026
• Authors: Agegnehu Kitanbo Yoshe
• DOI: 10.21926/aeer.2601003

Research Groups

• Department of Water Resources and Irrigation Engineering, Arba Minich University, Arba Minich, Ethiopia.
• Siberian School of Geosciences, Irkutsk National Research Technical University, Irkutsk, Russia.
• Journal of Asian Scientific Research, New York City, New York, USA.

Short Summary

This study develops a GRACE-based drought index (GRDI/WSDI) to characterize hydrological drought in the Ethiopian Rift Valley Basin, demonstrating that integrated terrestrial water storage data captures severe deficits and groundwater depletion more effectively than traditional meteorological indices. The findings reveal that droughts in the region have become increasingly frequent and severe, with extreme water storage deficits recorded in 2013 and 2014.

Objective

• To analyze water storage deficits and develop a GRACE-based drought index (GRDI/WSDI) for the Rift Valley Basin.
• To evaluate drought severity, duration, and cumulative impacts by comparing satellite-derived indices with conventional meteorological and hydrological indices (SPI, SPEI, SRI, ESI, and EDDI).

Study Configuration

• Spatial Scale: Rift Valley Basin, Ethiopia (Geographic coordinates: 36°–40° E and 4°–9° N; Elevation range: 500 m to 4181 m).
• Temporal Scale: Primary analysis from 2002 to 2016 (GRACE period); extended historical and comparative analysis from 1991 to 2021.

Methodology and Data

• Models used: Autoregressive Integrated Moving Average (ARIMA (1, 0, 0) (1, 1, 0)) for time-series forecasting; Hargreaves equation for Potential Evapotranspiration (PET) estimation.
• Data sources:
  • Satellite: GRACE (Gravity Recovery and Climate Experiment) terrestrial water storage (TWS) anomalies from CSR (University of Texas), GFZ (Potsdam), and JPL (NASA).
  • Reanalysis/Gridded Dataset: TerraClimate (0.5° resolution) for precipitation, actual evapotranspiration, and surface runoff.
• Indices Evaluated: Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Standardized Runoff Index (SRI), Evaporative Stress Index (ESI), Evaporative Demand Drought Index (EDDI), and the Water Storage Deficit Index (WSDI/GRDI).

Main Results

• Water Storage Dynamics: The maximum TWS anomaly was 0.0619 m/yr (2014), and the minimum was 0.0437 m/yr (2011). A strong correlation (0.96) was found between cumulative precipitation and cumulative water storage deficit.
• Drought Identification: The GRACE-based index (GRDI) identified 13 major drought events between 2002 and 2016. Extreme drought conditions were specifically captured in 2013 and 2014, with total drought indices of 10.3 and 15.9, respectively.
• Index Comparison: SPI, SPEI, SRI, and ESI showed strong agreement (cross-correlation coefficients > 0.82), while GRDI uniquely identified large-scale subsurface water storage deficits and groundwater depletion.
• Model Performance: The ARIMA forecasting model achieved a correlation coefficient (R) of 0.89 and a Nash-Sutcliffe Efficiency (NSE) of 0.85, with a Mean Absolute Error (MAE) of 0.1468 m.
• Temporal Trends: Droughts in the basin have become more frequent and prolonged, with the longest events persisting for 12 consecutive months (e.g., in 2013, 2014, and 2021).

Contributions

• This research represents the first application of GRACE-based terrestrial water storage data to estimate drought indices specifically within the Ethiopian Rift Valley Basin.
• It introduces a holistic monitoring framework that integrates surface water, soil moisture, and groundwater, overcoming the limitations of traditional meteorological indices in data-scarce regions.
• The study provides actionable insights for regional water resource management and early warning systems by quantifying the delayed response of subsurface water to precipitation variability.

Funding

• Not explicitly mentioned (the author declared that they performed all research work and no competing interests exist).

Citation

@article{Yoshe2026Characterization,
  author = {Yoshe, Agegnehu Kitanbo},
  title = {Characterization of Drought Severity Using GRACE and TerraClimate Dataset in the Rift Valley Basin, Ethiopia},
  journal = {Advances in Environmental and Engineering Research},
  year = {2026},
  doi = {10.21926/aeer.2601003},
  url = {https://doi.org/10.21926/aeer.2601003}
}

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