Extensive review of evapotranspiration estimation methodologies over a semi-arid region

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 both the advantages and disadvantages of remotely sensed ET estimation techniques, with detailed description on the Residual Approach to Surface Energy Balance and Simplified Empirical Regression. Key models reviewed include SEBI, S-SEBI, SEBAL, METRIC, SEBS, SSEB-op, the Modified Priestely-Taylor Method, and VI-Ts Triangle/trapezoidal space methods. The review critically goes through the diverse data source and their needs for enhancement in the ET estimation, particularly for semi-arid regions. Moreover, it discusses the different types of remote sensing data available for enhancing the accuracy of ET estimation, especially for semi-arid areas, and it discusses the variety of issues and uncertainties associated with remote sensing ET models, including terrain feature precision and near-surface meteorological data gaps. Finally, this study addresses future trends and opportunities in remote sensing technology and methodology that will eventually help to overcome some of the limitations of current remote sensing methods for improving ET estimation and ultimately enhance the management of our world’s water resources.