Analyzing the extent of drought in the Rajasthan state of India using vegetation condition index and standardized precipitation index

Drought is the most complex but least understood of all natural hazards that impacts around 55 million people globally every year. A hydrological drought (drought here after) is when the lack of rainfall goes on long enough to empty rivers and lower water tables and causes severe water shortage. In recent years, Geographic Information System (GIS) and remote sensing (RS) have played a crucial role in studying different hazards either natural or man-made. This study stresses upon the use of RS technique for drought risk assessment in Rajasthan state of India for the year 2002 and 2019. In this study, an effort has been made to analyze the extent of drought using two drought indices, namely vegetation-based vegetation condition index (VCI) and meteorology-based standardized precipitation index (SPI). For VCI calculation, which indicates impact of soil moisture on vegetation, we used moderate resolution imaging spectroradiometer (MODIS), Normalized difference vegetation index (NDVI) data from year 2000 to 2019. Monthly SPI was calculated using rainfall data obtained from the Rajasthan water resource department. SPI values were interpolated to get the spatial pattern of meteorological drought. Whole area categorised into five drought classes including extreme drought, severe drought, moderate drought, mild drought and no drought, following the recommended value breaks. The results revealed that about 83.87% area was under drought in the year 2002 thus considered as drought year. It has also been calculated that only 15.62% area was showing drought condition in year 2019 especially in the western part of Rajasthan. Correlation analysis performed between VCI and SPI resulted in a coefficient of correlation of 0.92 and 0.79 in year 2002 and 2019, respectively. The high correlation endorses the reliability of RS data for drought-related analysis.