Abstract <p>Geosystem–hydrological studies encompass a wide range of methods within the geographic–hydrological field. For analyzing the formation of surface runoff on the southern coast of Lake Baikal, the basin concept, as well as landscape–hydrological and structural–hydrographic approaches, is applied. The primary spatial unit of analysis is the river basin, considered together with the landscape structure and the parameters of the hydrographic network. This study is aimed at determining the landscape and hydrographic conditions and features of the formation of surface runoff in the area. As a result, runoff-forming, runoff-regulating, transit, and accumulation landscape complexes are identified; areas of runoff formation, transit, and accumulation are identified; and the territory is zoned according to the conditions and magnitude of runoff formation. This study is primarily of fundamental importance, aimed at identifying patterns in the structure of river systems that determine runoff areas and which are expressed in the orographic and landscape features of the basin. The practical significance of the calculations lies in the indicative assessment of possible runoff, primarily in the mountainous part of river basins, under conditions of uneven distribution of the standard observation network sections and their insufficient duration. The identification of runoff formation areas and assessment of potential runoff from these areas can be used to develop recommendations for rational planning and use of basin lands, as well as to prevent the occurrence of negative natural consequences.</p>