According to space sounding data using the MNDWI index, the dynamics of changes in the water surface of 17 lakes in the Eravno-Khorginsky system over the past 30 years has been determined. The greatest drying up of the lakes occurs in 2020, some lakes have completely dried up. The water surface of Lake Mal. Eravnoe, the second largest in the system, decreased from 62.57 km2 in 1991 to 5.26 km2 in 2020. Currently, all the lakes are closed, previously the largest, excluding the lake Gunda, at high levels they were connected by a channel and had a runoff in the river Vitim. Nevertheless, the areas of water areas of the lakes varied consistently, the correlation coefficients between all lakes varied in the range of 0.46-0.99. To clarify the main factors affecting the drying of lakes, in addition to the data on atmospheric precipitation and air temperature, the calculated hydrothermal moisture coefficient G.T. Selyaninov and aridity index D.A. Pedya. Correlation analysis showed that the increase in air temperature over the past three decades has a more major impact on the reduction of the lake water area.