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Assessment of Flash Droughts in the Kashkadarya Region, Uzbekistan〇Valeriya RAKHMATOVA, Kenji TANAKA, Temur KHUJANAZAROVThe Kashkadarya River Basin is situated in the southern

The introductory segment provides an overview ofregion of Uzbekistan. It plays a crucial role in overall

the region's vulnerability to climate change, emphasizing

water supply, offering essential resources for irrigation

the critical nature of water scarcity. This study seeks toand agriculture in the Kashkadarya Valley. The riveroriginates primarily from scarce precipitation of thePamir-Alay Mountain system. The river runoff of theKashkadarya River Basin is formed at the westernextremities of the Zarafshan and Gissar mountain ranges.

assess the intensity of flash droughts in the Kashkadarya
region, unraveling patterns and potential implications foragriculture. The methodology includes the computation of
the Flash Drought Intensity Index, covering the period
from March to September between 1990 and 2020.

The intensive agricultural practices in the region
demand substantial water volumes during the summer,
which face limitations due to the arid climate. Unlike
other river basins nearby, the Kashkadarya River lacks
substantial glaciers to augment water supply during thehigh vegetation season. Additionally, it's noteworthy thatthe available free land in the Kashkadarya Valley
surpasses the area that river waters can irrigate. To
enhance water supply an, extra water is transferred fromthe basins of the Zarafshan and Amu Darya rivers (fig. 1).
The region faces an escalating challenge inmanaging water resources due to flash droughts. This

Fig. 1. Kashkadarya River basin. Source: wikimedia

Methodphenomenon, characterized by rapid and severe waterThe Flash drought intensity index (FDII) (Otkin et al.

deficit in fast and short temperature rise (heat wave), has2021) accounts for both the unusually rapid rate of

become a pressing concern, especially considering thatdrought intensification and its resultant severity. FDII

approximately 90% of the region's water is allocated toincludes two components: one that measures the rate ofagriculture. The existing water distribution system relies

intensification (FD_INT) and a second that captures theon early-season hydrological forecasts, urgently requiring

drought severity (DRO_SEV).

innovative strategies to address water scarcity issues. ThisFor that study, a minimum intensification rate

research postulates that a real-time monitoring system forequivalent to a 15th percentile decrease (ΔPER_BASE) inflash droughts can play a pivotal role in identifying areas

soil moisture during a 4-pentad period (ΔT_BASE) was

experiencing or nearing plant stress. The proposed

required: 𝐹𝐷_𝐼𝑁𝑇 =__×__strategy involves timely irrigation in stressed regions andSimilarly, the baseline percentile threshold used tothe postponement of irrigation in “healthier” areas,represent the onset of drought conditions (DRO_BASE)

thereby optimizing water resource management.

was set at the 20th percentile of the distribution:

𝐷𝑅𝑂_𝑆𝐸𝑉 =∑(𝐷𝑅𝑂_𝐵𝐴𝑆𝐸 − 𝐷𝑅𝑂_𝑂𝐵𝑆(𝑛)),whereareas where plants are under stress or on the brink of stress

np is the number of pentads,conditions, timely irrigation interventions can be

DRO_OBS(n) is the observed percentile for pentad n.

strategically implemented to mitigate adverse impacts onIn cases where intensification or severity does notcropyields.

meet the aforementioned minimum requirements, theseparameters should be set to zero. Finally, the FDII is thencomputed as the product of the FD_INT and DRO_SEV
components/.
The Agricultural Stress Index (ASI) is a rapid
indicator for early detection of cropland and grassland
facing a high probability of water stress, commonly called
drought. This index integrates the Vegetation HealthIndex (VHI) in two critical dimensions for evaluating
agricultural drought events: temporal and spatial. The
initial step involves temporal averaging of the VHI,
assessing the intensity and duration of dry periods at theFig. 2. Comparing drought severity with vegetation index.
a) Drought severity in Uzbekistan b) ASI for croplands

Conclusion

pixel level during the crop cycle. The subsequent stepThis research significantly contributes to thedetermines the spatial extent of drought events byevolving landscape of water resource management in thecalculating the percentage of pixels in arable areas with a

Kashkadarya region. The integration of flash drought

VHI value below 35 percent, a critical threshold identified

monitoring into decision-making processes seeks toin previous research (Kogan 1995). Administrative

elevate water use efficiency in agriculture, fostering

regions are then classified based on the percentage of thesustainable practices amidst the challenges posed byaffected area, facilitating quick interpretation of theclimate change. Future endeavors will focus on refining

results.

the real-time monitoring system and undertaking on-theground validation to ensure the practical applicability ofResults
To

comprehensively

understandthefactors

influencing flash drought occurrences, an analysis
involvingcomparisons

withairtemperature,

evapotranspiration, and radiative temperature. The
correlation of the indexes with key indicators, such as theNormalized Difference Vegetation Index (NDVI) andAgriculture Stress Index (ASI), was applied to assess theimpact of flash droughts on plant conditions. Preliminary
findings suggest a discernible correlation between flash
drought severity and radiative temperature, hinting at apotential climatic influence on their occurrence.
Further analyses, incorporating NDVI and ASI,
unveiled

distinct

patternsofvegetationstresscorresponding to flash drought events (fig 2). Theseoutcomes substantiate the proposed irrigation strategy,
which hinges on flash drought monitoring. By identifying

the proposed irrigation strategy. This study advances ourunderstandingofflash

drought

implicationsforagricultural regions and provides a robust foundation for
the formulation of climate-resilient water management
strategies.
References
Kogan, F. N. 1995. “Application of Vegetation Index andBrightness Temperature for Drought Detection.”
Advances in Space Research: The Official Journalof the Committee on Space Research 15 (11): 91–100.
Otkin, Jason A., Yafang Zhong, Eric D. Hunt, Jordan I.
Christian, Jeffrey B. Basara, Hanh Nguyen,Matthew C. Wheeler, et al. 2021. “Developmentof a Flash Drought Intensity Index.” Atmosphere12 (6): 741.