Under a warming climate, significant changes are anticipated in the water cycle. This, in turn, would impact the water balance of large heterogeneous landscapes like river basins. In this context, evapotranspiration emerges as a pivotal component that determines water availability within landscapes. This study focuses on the upper part of the Gundar River basin, one of the largest river basins in the state of Tamil Nadu, India, characterized by dry weather during summer and high levels of agriculture during the wet season, along with the presence of Prosopis juliflora, an invasive species. Land cover changes act as primary drivers of evapotranspiration, and this study aims to conduct a comparative analysis of land cover changes within the study area between the summer and northeast monsoon seasons – spanning the years 2006, 2014, and 2021. In addition, the study utilizes the Surface Energy Balance Algorithm for Land (SEBAL) model to estimate evapotranspiration at a resolution of 30m, leveraging Landsat imagery, in-situ weather data, and GLDAS datasets both inter- and intra-seasonally. Considering the land cover classes as units of comparison, an intermodal comparison is conducted using the EEFlux ET product, present at the same resolution, assessing agreement among datasets due to the absence of in-situ validation data. Lastly, the study calculates mean water outflux for the day by integrating results from land cover classification and mean evapotranspiration estimates derived from SEBAL, to understand the variability of water outflux caused due to changes in land cover and the subsequent ET estimates.