Studying the effects of drought on vegetation changes in rangeland and agricultural areas based on field and satellite data (Case study: Southern part of Hamadan Province)

The impact of drought can be water supplies decrement, agricultural production reduction, changes in vegetation and rangeland area or desertification accelerating. Quantify the effects of drought indices are necessary for drought episodes monitoring. Based on accessible data type into two general these indices were divided in two categories: terrestrial and satellite.The aim of this study was to compare the diagnosis and classification ability of vegetation changes which have occurred as a result of drought. The SPI used as earth index and WSVI, TCI, VCI and VDI used as satellite indices for monitoring vegetation change in the southern part of Hamadan Province. For this purpose, the indices were extracted from Landsat TM and images and the correlation between them done based on Pearson correlation. The results showed that the highest and lowest correlations with the drought variables at the studied years were achieved with VDI and TCI indices respectively. Compared to meteorological methods, the satellite images have advantages such as wider coverage, higher temporal resolution and lower cost. So, the use of remote sensing is recommended.