Formation conditions of fresh groundwater deposits in Irkutsk artesian basin

The purpose of the research is to give a detailed description of hydrogeological conditions of the Irkutsk artesian basin, which is a large hydrogeological structure of the second order. The method of morphostructural analysis has been used to distinguish the territories with different formation conditions of fresh groundwater deposits as well as to identify the boundaries of large lowlands and uplands in comparison with the geological structure. To make a generalization, the author uses the data on 45 deposits of fresh drinking groundwater explored on the territory of the Irkutsk artesian basin of the second order with the operational reserves of more than 500 m 3 /day. Deposits of fresh groundwater in Jurassic terrigenous rocks are confined to large relief elevations within tectonic depressions while the deposits in both Cambrian carbonate and Jurassic-Ordovician terrigenous sediments are confined to tectonic uplifts.The deposits are replenished by natural resources. The production horizons of large deposits in Cambrian and Ordovician rocks are fed by attracted resources. In the lowlands the deposits of fresh groundwater are formed only in Quaternary alluvial deposits, due to infiltration from rivers (attracted resources). Neotectonic movements are the ones that had a dominant influence on the formation of natural resources and dynamic reserves as well as on underground flow localization as they ensured the distribution and localization of surface and underground flow. It is also noted that when identifying promising areas for searching for fresh underground water, it is advisable to rely on the distribution patterns of fresh underground water reserves of already explored deposits within the identified morphostructures.