The map is based on generalizing materials of the Institute of the Earth's Crust, and the Geological Surveys of Buryatia, Chita and Irkutsk using hydrogeological maps of 1:5000000 [Atlas..., 1983] and 1:4500000 scales [National Atlas ..., 1990].
During mapping the method of mapping the main aquifers (hydrogeological formations) was applied. Aquifers are distinguished according to structural and hydrogeological features, the prevailing type of water-ermeability, and reservoir properties of rocks.
In the Baikal basin pore-edge waters, confined to loose unconsolidated sediments of Mesozoic and Cenozoic age, have a wide distribution, as well as crack waters in all lithified metamorphic, igneous and sedimentary rocks of different ages from the Archaean to the end of the Paleozoic - Mesozoic inclusive.
Hydrogeologically, the Baikal basin is a complex system of artesian basins and hydrogeological massifs. Artesian basins occupy intermontane depressions composed of loose rocks of the sedimentary cover and crystalline basement rocks. They are characterized by pore-edge waters of the zone of active water exchange and crack waters, often pressure waters, and foundation waters. Hydrogeological massifs are composed with crystalline rocks of mountain- folded frame and can accommodate crack waters of exogenous fissuring. Thickness of the zone of active water exchange does not exceed 100-150 m.
Most watered are karst carbonate rocks, as well as zones of tectonic dislocations, intersecting the cropping-out foundation or spread along the contacts of sedimentary-metamorphic rocks with igneous and metamorphic rocks. They are often traced by upward unloading both of cold and thermal waters.
Atlas of hydrogeological and engineering-geological maps of the USSR. Scale 1:5000000. (1983).
National Atlas of the Mongolian People's Republic, scale 1:4500000. (1990).