Agricultural Drought Monitoring Using Meteorological Indices in Darreh Dozdan Basin, Iran

The objectives of this study are to monitor and assess agricultural drought using SPI, aSPI, RDI, and eRDI indices in the Darreh Dozdan River Basin while comparing the performance of gamma and log-normal distributions in estimating the values of these indices. In this study, monthly meteorological data from the Kuhdasht synoptic station for the years 1998 to 2022 were used. Effective precipitation and potential evapotranspiration were estimated using the CROPWAT 8.0 model. Drought indices were estimated using DrinC 1.7 software. The findings indicate that the Darreh Dozdan River Basin has experienced agricultural droughts for 4, 8, 8, and 7 years, respectively, with varying intensities based on the SPI, aSPI, RDI, and eRDI indices. The agricultural drought assessment of the Darreh Dozdan River Basin shows that although the climate has been relatively stable in most years, the occurrence of multiple droughts increases the need for planning and management of water resources in agriculture. The results comparing the performance of the gamma and the log-normal distributions showed that both distributions estimate the values of agricultural drought indices close to each other, so that the drought classification for all indices is the same in the two distributions.