Spectral Drought Indices: A Methodology for Detecting Basin-Wide Drought

Drought is a normal disaster that profoundly impacts several factors, including the economy, agriculture, environment, and society. Using spectral indices from Landsat, the current research evaluated droughts' magnitude and frequency in the Diyala River Catchment, Iraq, during the growing season for 2013 through 2022. Fifteen mosaics were created over ten years using forty images in TM and ETM+ (167/36 and 168/37) that had been gathered from 2013 to 2022. The scenes are from two Landsat time series. The drought situation was assessed using the Normalized Difference Vegetation Index (NDVI), Vegetation Condition Index, and Normalized Difference Water Index. The research's findings revealed a rise in the DRC's occurrence and severity of drought over the past ten years, especially in 2000 and 2008. However, between 2021 and 2022, the total vegetation covered based on NDVI decreased by 20.67% and 36.33%, respectively. In 2021 and 2022, the vegetation cover significantly decreased (54.3% and 29.5%, respectively). Derbendekan and Hemrin lakes, conversely, experienced declines of 15.1%, 7.12%, 108.38%, and 143.33% in 2021 and 2022, respectively. Between 2013 and 2022, the DRC experienced an increase in drought, a decline in water body surface area, and a decrease in precipitation averages.