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This study examines the dynamics of flash and long-term droughts in the Danube River Basin.

January 14, 2026International Journal of Climatology0 citationsOpen Access

Intensification of Flash and Long‐Term Droughts in the Danube River Basin: A Multi‐Scale Analysis Using Satellite‐Derived Evaporative Stress Index and Soil Water Index

JPJana PolákováCzech University of Life Sciences Prague TTT. TrifanCzech University of Life Sciences Prague

Key Points

This study examines the dynamics of flash and long-term droughts in the Danube River Basin.
Analyzes satellite-derived indices: Evaporative Stress Index and Soil Water Index.
Uses data from 2001 to 2024 for ESI at 4-week and 12-week intervals, and SWI at 40 cm and 100 cm depths.
Identifies patterns of drought intensification across eight countries.
Identifies increasing drought-related damages exceeding 10 billion EUR in Romania and Moldova.
Finds 18% increase in flash drought frequency, with distinct spatiotemporal patterns noted.
Demonstrates ESI-4Wk can detect flash droughts 3 weeks earlier than SWI-40.

Abstract

ABSTRACT The Danube River Basin (DRB), a critical agricultural and ecological region in Europe, faces escalating risks from intensifying flash droughts (FD) and long‐term droughts (LTD), driven by accelerating climate change. The 2024 drought highlighted these challenges. It caused major socio‐economic losses, particularly in Romania and the Republic of Moldova. In these countries, drought‐related damages over the past 4 years exceeded 10 billion EUR. This study investigates the spatiotemporal dynamics of droughts across eight DRB countries—Austria, the Czech Republic, Slovakia, Hungary, Slovenia, Bulgaria, Romania, and the Republic of Moldova—using satellite‐derived indices: the Evaporative Stress Index (ESI) at 4‐week (ESI‐4Wk) and 12‐week (ESI‐12Wk) intervals (2001–2024). Additionally, the Soil Water Index (SWI) at depths of 40 cm (SWI‐40) and 100 cm (SWI‐100) was used to analyse the multi‐layer soil moisture characteristics (2007–2024). Firstly, a key innovation is the development of FD criteria based on seven‐day averages of ESI‐4Wk and SWI‐40, which effectively capture rapid‐onset atmospheric stress and surface soil moisture deficits. Secondly, the findings reveal distinct spatiotemporal patterns of drought intensification, characterised by a pronounced west–east dipole in the distribution of ESI and SWI. Thirdly, southeastern DRB regions—Hungary, Romania, and the Republic of Moldova—emerged as FD hotspots, with FD frequency increasing by 18% and coupled atmospheric‐soil droughts showing minimal lag. Fourthly, case studies of the 2022 and 2024 droughts demonstrate ESI‐4Wk's early FD detection (3 weeks ahead of SWI‐40) and SWI‐100's utility in tracking post‐recovery soil depletion. Finally, this framework elucidates the cascading impacts of drought, linking atmospheric stress to soil moisture persistence, and provides a scalable approach for monitoring compound hydroclimatic extremes.

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