The problem of assessing the ecological status of natural objects is one of the most important fundamental problems of modern geographical and geoecological studies. Interest in the integral assessment of ecological status is due to the need to obtain quantitative assessments of the state of eco- and geosystems and their integrative properties, their transformations under the influence of external influences. Studies of assessing the ecological status of water bodies are currently being developed in the EU and the Russian Federation based on multicriteria and integrated assessment methods. The article discusses the theoretical and methodological principles developed by the authors and the methodology for the integrated assessment of the ecological status of water bodies on the example of small lakes in the northwestern Ladoga area. An integrated assessment of the ecological status includes several stages: 1 – an integrated assessment of the trophic status of a water object, 2 – an integrated assessment of the quality and toxic pollution of water, 3 – an integrated assessment of the potential sustainability of a water object. At the next stage, the second level of convolution is performed to obtain an integral indicator of environmental status. The article discusses the issues of building multi-level and multi-criteria classifications of environmental status, stages and results of the study. Three hypotheses are considered to take into account the sustainability of water bodies in the construction of integral indicators of ecological status. The construction of integral indicators of ecological status was carried out on the example of Lake Suuri in the Leningrad Region for 2016-2018.