Surface water monitoring using remote sensing images is important for understanding the impact of water on global ecosystems and climate change. Environmental changes and human interventions lead to significant environmental impacts that must be considered. Today, remote sensing satellite images have helped to monitor changes in various issues, including environmental issues. Using Landsat-5 and Landsat-8 images and the NDWI index, this research has investigated the changes in Bakhtegan Lake over two decades. The results show that the lake has dried up and, according to the "from-to" maps, a large percentage of the water has turned into salt, so the calculated lake's water surface area has decreased from 505 square kilometres in 2000 to almost 0 square kilometres by 2022. Therefore, the potential factors affecting lake changes were investigated using MODIS, GPM, FLDAS, and GRACE data. The results indicate that the changes in temperature, evaporation, and transpiration did not play an important role in the drying of the lake, but the reduction in the underground water level due to the digging of deep wells is known as the main cause of the drying of the lake. In order to restore the lake and prevent the transformation of salts into dust, it is suggested to prevent the extraction of water through well pumping in the catchment area of ​​the lake and to limit its use for agricultural purposes.