Meteorological and Hydrological Drought Survey Using the SPI, SDI and PNI Indices in The Province of Kurdistan

Drought is one of the most destructive environmental phenomena that causes extreme damages to the natural resources and human lives. As the Province of Kurdistan supplies many agricultural products in the country, the occurrence of drought is very important and that is the main reason behind the execution of this study. The data of twenty-three hydrometric and seven synoptic stations were used in a 29-year common statistical period (1985-2013). To calculate the meteorological drought, the SPI and PNI indices, and for the hydrological drought, the SDI index were used at the annual time scale. Results of the Mann-Kendall and Thilson tests indicated the existence of a trend for the meteorological drought at Sanandaj, Marivan, Ghorveh, Zarrineh and Saqez Stations. Also, the running of this test on the SDI index indicated a downward trend in all of the hydrometric stations, except for the Sentin Khorokhoreh, Ghashlagh, Qeblv and Meyar stations. Results also showed that the root mean square error for SPI, PNI, and SDI were 0.41, 0.49 and 0.47, and the coefficient of determination (R2) were 0.65, 0.51 and 0.59, respectively. Therefore, the SPI index is the best function among these three.