Investigation on spatial variations of drought using geostatistics in Kerman province over a thirty-year period (1970- 2000)

This study was performed in order to determine spatial variations of drought in Kerman province by Standard Precipitation Index (SPI) and comparing interpolation methods of Kriging and inverse distance weight with powers of 1 to 5, over a thirty-year period (1970-71 to 2000-2001). According to the results during the study period (10-year intervals), maximum and minimum average amounts of SPI were respectively recorded for 1990-91 and 2000-2001. In all studied years, exponential model was determined to be the best variogram fitted to the spatial structure of data and the effective range of each station was a distance of almost 18.03 kilometers for all years except 1990-91 with an effective range of 5, 02 km. Cross validation techniques introduced Kriging as the best interpolation method for all years except 1990-91 in which IDW to the power of 5 was the best interpolation method. Spatial zoning map of SPI showed that moderate drought was recorded for southern parts of Kerman province such as Anbarabad and Jiroft in 1970-71 while in other parts of the province slight drought was observed except Rafsanjan. In 1980-81, slight drought was observed for most parts of the province while in Bam, Bardsir and east of Jiroft slight moisture was observed. In 1990-91, there was a slight drought was recorded for Kerman, Baft, Kahnooj and east of Jiroft. In 2000-2001, all parts of the province were at risk of drought as in the southern half of the province (Baft, Anbarabad and Kahnoj) moderate drought and in the northern half of the province(Kerman, Rafsanjan and Bardsir) slight drought were observed. Error maps showed considerable accuracy of interpolation, especially near the stations.