Drought monitoring using spectral and meteorological based indices combination: a case study in Sulaimaniyah, Kurdistan region of Iraq

Drought has dramatically affected Iraq throughout the last decades, which were characterized by a large drop in rainfall, and its main rivers discharge in general. Three spectral indices were derived from the Landsat images of 1990, 2007, and 2008 as indices of soil, vegetation, and moisture to monitor the drought and its impacts. The derived indices were the Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST), and the Normalized Differential Water Index (NDWI). The fourth drought index was the Standardized Precipitation Index (SPI), which has been used as a meteorological drought index. The aim of this chapter is to investigate the role of integration of vegetation indices (NDVI in this study) and SPI as a combined index (NDVI-SPI) for drought monitoring in Sulaimaniyah, Kurdistan region of Iraq in 1990, 2007, and 2008. The results showed a significant decrease in the vegetative cover by 28.6% in 2008 in compared with that of 2007. However, results of the combined NDVI-SPI indices maps emphasized the harsh impact of drought on the vegetative cover, which occurred in 2008. In particular, the results revealed a significant increase in areas of the extreme, severe, moderate drought classes in 2008 by percentage of 81.2% more than in 2007. On the other hand, Dukan Lake’s surface area in the study site suffered a significantly shrunk by 16.5 and 32.5% in 2007 and 2008, respectively, compared with its total size in 1990. The study concluded that the use of a combination of NDVI-SPI indices provides more reliable results for drought monitoring than any single index in the study area