Evapotranspiration (ET) is a key element in the hydrological cycle. It has a high impact on climate studies, agricultural productivity, and water resource management. Despite its importance, the accurate estimation of ET over semi-arid areas continues to be difficult, mainly due to heterogeneity in land surface properties and large variations in weather patterns. This study follows the PRISMA framework to systematically review 174 full-text publications from 1971 to 2025. The review summarizes b