Vulnerability of Yazd Province in Drought Using Standardized Precipitation Index and Geostatistical Methods

Standardized Precipitation Index (SPI) has been widely used for evaluation of drought. Different time scales of SPI could be used e. g.، 3، 6، 9، 12، 18، 24 and 48-months. SPI 12-month is used for evaluation of drought condition and vulnerability of drought in the study area. SPI 12-month was computed in 28 stations based on 30 years of data period in the study area. Spatial distribution of SPI 12-month was analyzed using different interpolation techniques of geostatistics. The precise interpolation technique was selected based on the cross-validation criteria. In order to access vulnerability of the study area in drought، two years were selected as end-members (1378-79 and 1377-78 for minimum and maximum precipitation، respectively) and 1376-77 was selected as average climatological condition due to annual precipitation values. The results show that in extreme year (1377-78)، more than 99٪ of the study area leave from the drought condition. However in minimum condition of annual precipitation (1378-79)، more than 98٪ of the study area belongs to drought. As a results، Yazd، Taft، Mehriz، Bafgh، Naibandan and Kharanagh show high vulnerability to drought in the Yazd Province.