بررسی کارایی شاخص‌ خشکسالی پوشش گیاهی (VDI) در حوضه کرخه

The increase in temperature and changes in precipitation patterns lead to extreme weather changes such as drought. Drought reduces soil moisture and affects vegetation and agricultural products. Drought monitoring through meteorological stations faces problems such as drought estimation in limited areas, short and irregular periods of time, for this reason, nowadays remote sensing drought indicators are widely used to monitor drought for large areas. Based on this, the purpose of this research is to investigate the effectiveness of the Vegetation Drought Index (VDI) index in identifying and analyzing agricultural drought in the Karkheh basin. In order to calculate this index, MODIS sensor images (MOD02HKM) were used in the three statistical years when the country faced the most drought stress. According to the results obtained based on the calculated VDI values, the occurrence of the most severe drought in 2016, 2018 and 2018 was confirmed. Also, the accuracy of the mentioned index was evaluated with the SPI index calculated in 11 rain and evapotranspiration gauge stations located in Karkheh basin. The results showed that there is a high correlation between the mentioned index and precipitation, which indicates the high efficiency of this index in the region, so this index can be a suitable index for estimating agricultural drought.