Rakhmatova et al. (2026) Comparative analysis of flash and traditional droughts in the Kashkadarya region, Uzbekistan

Identification

• Journal: Hydrological Research Letters
• Year: 2026
• Date: 2026-01-01
• Authors: Valeriya Rakhmatova, Temur Khujanazarov, Kenji Tanaka, Yoshiya Touge, Bakhriddin Nishonov, Dmitry Belikov
• DOI: 10.3178/hrl.25-00021

Research Groups

• Graduate School of Engineering, Kyoto University, Japan
• Disaster Prevention Research Institute, Kyoto University, Japan
• Hydrometeorological Research Institute, Uzbekistan
• Center for Environmental Remote Sensing, Chiba University, Japan

Short Summary

This study comparatively analyzed flash and traditional droughts in Uzbekistan's Kashkadarya region (1990-2019) using root-zone soil moisture data, revealing distinct characteristics and an intensifying frequency and severity of both drought types, particularly in dryland and pasture zones.

Objective

• To comparatively analyze flash and traditional droughts in the Kashkadarya region, Uzbekistan, focusing on soil moisture dynamics across contrasting land use types.
• To identify differences in drought progression mechanisms, seasonal timing, and drivers between flash and traditional droughts.

Study Configuration

• Spatial Scale: Kashkadarya region, Uzbekistan (approximately 28,570 km²), with analysis at 1 km resolution for SiBUC and 0.25° for CCISM. Four representative land categories were studied: Drylands, Foothills, Irrigated area, and Pastures.
• Temporal Scale: 1990 to 2019 (30-year baseline period), using daily root-zone soil moisture data.

Methodology and Data

• Models used:
  • SiBUC (Simple Biosphere model, incorporating the Urban Canopy component) land surface model.
  • H-TESSEL land surface scheme (used in ERA5-Land reanalysis).
• Data sources:
  • Root-zone soil moisture (SM) data from the SiBUC land surface model.
  • ERA5-Land reanalysis dataset (root-zone SM at 7–28 cm depth, surface SM).
  • ESA Climate Change Initiative Soil Moisture (CCISM) v9.1 products (satellite-derived surface SM at 2–5 cm depth, 0.25° resolution).
  • Meteorological forcing for SiBUC from the GSWP3 global reanalysis dataset.
  • Temperature and precipitation anomalies.
  • FAO irrigation masks and Leaf Area Index (LAI) values for refining irrigated zone boundaries.
  • Soil types and land-use characteristics.

Main Results

• Flash droughts typically developed in spring under combined short-term precipitation deficits and elevated temperatures, leading to rapid soil moisture depletion during critical vegetation growth.
• Traditional droughts evolved more gradually due to sustained precipitation deficits, exhibiting longer durations (30–40 weeks) and greater spatial extent.
• Traditional droughts were associated with more severe soil moisture anomalies (often below –0.6), while flash droughts showed more moderate anomalies (between –0.5 and –0.1) and were more localized.
• Model comparisons indicated that ERA5-Land strongly overestimates wet-season soil moisture, whereas SiBUC showed a weaker positive bias when compared to CCISM.
• All datasets consistently confirmed an intensifying drought frequency and severity in recent decades, particularly in dryland and pasture zones.
• Even irrigated areas showed more frequent occurrences of soil moisture falling below the 40th percentile in the 2010s, indicating increasing stress despite supplemental water.

Contributions

• Provides a novel comparative analysis of flash and traditional droughts in the arid Kashkadarya region of Uzbekistan, distinguishing their unique progression mechanisms, seasonal timing, and meteorological drivers.
• Highlights the critical importance of high-resolution soil moisture data for enhancing drought monitoring, early warning systems, and developing targeted adaptation strategies in water-stressed agricultural regions.
• Evaluates the consistency and limitations of different soil moisture datasets (SiBUC, ERA5-Land, CCISM) in characterizing drought dynamics, offering insights into data source uncertainties.
• Offers a nuanced framework for understanding regional drought risk by differentiating between rapid-onset, meteorology-driven flash droughts and prolonged, precipitation-dominated traditional droughts.

Funding

This research was supported by the Science and Technology Research Partnership for Sustainable Development (SATREPS) in collaboration between the Japan Science and Technology Agency (JST, JPMJSA2001) and the Japan International Cooperation Agency (JICA).

Citation

@article{Rakhmatova2026Comparative,
  author = {Rakhmatova, Valeriya and Khujanazarov, Temur and Tanaka, Kenji and Touge, Yoshiya and Nishonov, Bakhriddin and Belikov, Dmitry},
  title = {Comparative analysis of flash and traditional droughts in the Kashkadarya region, Uzbekistan},
  journal = {Hydrological Research Letters},
  year = {2026},
  doi = {10.3178/hrl.25-00021},
  url = {https://doi.org/10.3178/hrl.25-00021}
}