This study estimates monthly variation of surface water volume of Thac Mo water reservoir, located in Binh Phuoc province, in South Vietnam, for the 2016–2021 period, using SAR Sentinel-1 observations and Jason-3 altimetry data. SAR Sentinel-1 observations have been pre-processed mainly using the Google Earth Engine cloud computing platform to estimate variation of surface water extent, while Jason-3 radar altimetry data has been processed using the AlTiS software to estimate variation of surface water level of the reservoir. Results show a very good agreement between variations of the reservoir's surface water volume derived from satellite data and that derived from in situ measurement, with a correlation of 95.4%.