Spatiotemporal analysis of land surface temperature and soil water stress in Erer Watershed of Wabi Shebelle River Basin, Ethiopia

Abstract

Understanding the land surface process in numerical models necessitates the consideration of Land Surface Temperature (LST) and soil moisture. LST plays a crucial role in regulating surface and sub-surface heat; thus, influencing water circulation within the atmosphere. This study utilized Landsat 8 Optical Land Imager (OLI) images with a 30 m resolution to analyze LST, Soil Moisture Index (SMI) and Vegetation Dryness Index (TVDI) for the Erer Watershed, which is in the Wabi Shebelle River basin in Ethiopia. The investigation spanned six years, from 2015 to 2021, and it involved determining the Normalized Difference Vegetation Index (NDVI) for each specified year to get LST, soil water stress, and TVDI. The thermal infrared band's digital values were converted into spectral radiance using the relation specified in the Landsat user's manual. The final LST was derived using surface emissivity based on NDVI classes. The findings revealed an increasing trend in LST, SMI, and TVDI over time, signifying decline in soil moisture. The north-eastern and north-western sections of the Erer Watershed exhibited the highest values of LST, SMI, and TVDI, with a negative correlation observed with soil moisture. The spatial distribution of LST, SMI, and TVDI can be used as a valuable reference for managing soil water stress and to understand ecosystem services. Additionally, LST may serve as a significant indicator in monitoring environmental changes, particularly in relation to drought, within the study area.