The decrease in the level of Lake Urmia is evidence of climate change and anthropogenicity. This decrease in level has led to an increase in salt area, salt storms and salinization of groundwater. It is one of the major environmental challenges in northwestern Iran. Fluctuations in lake level, decrease in water level of plains and decrease in river discharge are evidences of hydrological changes in Urmia Lake basin. The present study tries to provide a clear picture of the water changes of Urmia Lake during the last three decades. Hydrological data and images of Landsat satellite for Urmia Lake basin in the period 1984-2017 were studied using remote sensing and statistical methods. The classification of satellite images was performed using the maximum likelihood method. According to the results, the highest decrease in the area of the lake between 2001 and 2013 happened. Also, the analysis of the results showed that along with the very important role of global warming on the water volume of Lake Urmia, humans have been able to be one of the most important regional factors in creating the challenge of Urmia Lake. In fact, the water problems of Urmia Lake, especially after 2001, are a combination of climatic and anthropogenic factors. Manuscript profile