The Standardized Precipitation–Evaporation Index (SPEI) was applied in orderto address the drought conditions under current and future climates in theJordan River region located in the southeastern Mediterranean area. In thefirst step, the SPEI was derived from spatially interpolated monthlyprecipitation and temperature data at multiple timescales: accumulatedprecipitation and monthly mean temperature were considered over a number oftimescales – for example 1, 3, and 6 months. To investigate the performanceof the drought index, correlation analyses were conducted with simulated soilmoisture and the Normalized Difference Vegetation Index (NDVI) obtained fromremote sensing. A comparison with the Standardized Precipitation Index (SPI),i.e., a drought index that does not incorporate temperature, was alsoconducted. The results show that the 6-month SPEI has the highest correlationwith simulated soil moisture and best explains the interannual variation ofthe monthly NDVI. Hence, a timescale of 6 months is the most appropriate whenaddressing vegetation growth in the semi-arid region. In the second step, the6-month SPEI was derived from three climate projections based on the Intergovernmental Panel onClimate Change emission scenario A1B. When comparing the period 2031–2060 with 1961–1990,it is shown that the percentage of time with moderate, severe and extremedrought conditions is projected to increase strongly. To address the impactof drought on the agricultural sector, the irrigation water demand duringcertain drought years was thereafter simulated with a hydrological model on aspatial resolution of 1 km. A large increase in the demand for irrigationwater was simulated, showing that the agricultural sector is expected tobecome even more vulnerable to drought in the future.
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