Drought Risk Assessment for an Agricultural Basin in Turkey using SPEI and SPI

The Konya province in the Central Anatolia Region of Turkey features a semi-arid climate with cold

winters and hot, dry summers. Although the annual precipitation of the Konya Closed Basin is

about 350 mm, the basin is considered one of the main agricultural regions of Turkey. Given the

effects of drought on crop yields and food security, evaluation of drought risks is crucial. This

study aims to describe historical as well as future drought characteristics of the Konya basin by

means of two widely used meteorological drought indices: the standardized precipitation index

(SPI) and the standardized precipitation-evapotranspiration index (SPEI). The indices were

calculated for different timescales (6–24-month timescale) to better assess agricultural drought

conditions. For the SPEI index, the potential evapotranspiration (PET) was calculated using the

Hargreaves and Samani method, commonly used in arid and semi-arid weather conditions. The

analysis was performed over the period 1980-2020 using precipitation and temperature data from

18 weather stations located within Konya Closed Basin. Based on drought classification by SPI and

SPEI, values equal to or lower than -2 are considered extreme droughts. The results show that the

number of extreme climatic drought periods at the considered stations within the Konya basin

based on SPI is higher than that based on SPEI. The findings also reveal that both SPEI and SPI

characterize a general increase in drought severity, areal extent, and frequency over 2000-2010

compared to those during 1980-1990, mostly because of the decreasing precipitation and to a

lesser extent rising potential evapotranspiration. To assess future drought frequencies, the

drought indices were calculated using precipitation and temperature data provided by 17 regional

climate models from the EUROCORDEX project. The results for both RCP 4.5 and RCP 8.5 scenarios

show significantly more frequent extreme and severe droughts, particularly for the second half of

the 21st century. Overall, this study implies that SPEI may be more appropriate than SPI to

monitor drought periods under climate change since potential evapotranspiration increases in a

warmer climate.

This work was developed under the scope of the InTheMED project. InTheMED is part of the PRIMA

program supported by the European Union’s Horizon 2020 research and innovation program

under grant agreement No 1923