Some material and data on the aquifer system in the vicinity of Listvyanka municipality are provided, along with stratification of hydrogeological section of the key site — Krestovaya valley. Listvyanka settlement is situated at the joint of the Irkutsk artesian basin and Baikal mountain-folded hydrogeological region. The peculiar hydrogeological conditions are caused by a combination of the environmental factors: the composition and jointing of water-bearing rocks, height above the Baikal level, position of the valley channels, and permafrost distribution. Fissure, fissure-formation, pore-fissure and pore-formation underground waters occur in crystalline and fine-grained deposits. They are calcium or magnesium hydrocarbonate in chemical composition with salinity not exceeding 0,5 g/L. Atmospheric precipitation is the main source of underground water recharge. Lake Baikal drains the underground waters as evidenced by their table which is inclined in its direction. The underground waters recharging the Baikal do not disturb the chemical stability of its water body owing to their low salinity, and chemical composition similar to that of the Baikal water.Keywords: underground water, aquifers, water chemical composition, spring output (yield of water supply source), permafrost.