Assessment of the Relationship Between NDVI-Based Actual Evapotranspiration by SEBS

Groundwater has emerged to be a formidable poverty reduction tool in many developing countries because it can be distributed to poor communities far more cheaply, quickly and easily. This study investigated the applicability of seasonal actual evapotranspiration (ETa) in modeling trends in water table depth level and vegetation cover using in the Zayanderud basin, Iran. To this end, the surface energy balance system (SEBS) algorithm was applied to estimate the changes in ETa. By this approach, atmospherically corrected moderate-resolution imaging spectroradiometer products from 2000 to 2017 were used to determine the sensitivity of SEBS, physiological characteristics, and environmental factors. We found that the variations in the actual evapotranspiration estimated by SEBS (SEBS ETa) are mostly influenced by meteorological factors, net radiation, land cover type, NDVI, and water table depth. The SEBS ETa in the western part of the basin showed a higher value than that in the eastern part. The annual ETa has temporally increased from 45.66 to 112.34 mm in the eastern area of the basin and 97.64 mm in the western areas. Also, SEBS ETa was evaluated in the western and eastern parts of the study site comparatively, but there was not a significant difference between evaporation and SEBS ETa of the two sides. The correlation of NDVI and groundwater levels with SEBS ETa was relatively stronger in wet seasons than in dry seasons. This difference may be attributed to a water availability mechanism according to which as the depth of groundwater raises, NDVI decreases, while SEBS ETa increases. Therefore, this study contributes to our enhanced understanding of the planning and management of groundwater over arid and semi arid ecosystem.