Abstract <p>The impact of forest cover disturbance on evapotranspiration changes within a river basin is highlighted. The dynamics of forest cover disturbance as a result of forest fires in the Nizhnyaya Tunguska River basin for 2001–2020 has been analyzed based on Landsat satellite imagery. It is found that, regarding the spatial aspect, evapotranspiration in the Nizhnyaya Tunguska River basin is differentiated between the test catchments, which differ in climatic conditions and vegetation cover. Concerning the temporal aspect, a decrease in the weighted average evapotranspiration is noted as the burned areas accumulated. It is revealed that the difference in the evapotranspiration decrease in undisturbed and disturbed areas depends both on the overall disturbance of the forest cover in the catchment area and on the area of current year burns, with the effect of fresh burned areas showing if their area is more than 3% of the catchment area.</p>