Formation features of the Svirsk fresh groundwater deposit

The object of the study is the Svirsk deposit of fresh groundwater located in the central part of the Irkutsk artesian basin of the second order, which is a part of the Angara-Lena artesian basin of the first order (Irkutsk region, Russia). Geologically, the area under investigation is located within the Pre-Sayan depression, which is complicated by the Irkutsk basement bench. The studied Svirsk hydraulic depression is confined to the tectonic crush zone of the Lower Cambrian carbonate rocks stripping from the mouth of the Kotikha river valley to the mouth of the Kamenka river valley between the bedrock slope and the Angara river (Bratsk reservoir since 1967). The purpose of this study is to study the formation features, supply sources and hydrogeochemical conditions of the deposit based on the analysis of hydrogeological work carried out over the period from 1968 to 2012. The research methodology includes the search for a site with high reservoir properties and high quality of groundwater meeting drinking requirements, which is located in the influence area of constant head boundaries (attracted resources of the Angara river) using a comprehensive geomorphological analysis. The described deposit is characterized by the aquifer thickness from 13 to 38.7 m, composed of karst carbonate deposits. The water conductivity coefficient is 1284–2500 m2/day, well flow rates vary from 4.88 l/s (422 m3/day) to 18.2 l/s (1572 m3/day) with a decrease of 0.78–1m respectively. The qualitative composition of groundwater meets the standards, whereas outside the field, quality indicators deteriorate. The authors have studied the neotectonic formation conditions of the deposit of underground drinking water, whose quality meets the requirements of the centralized water supply, the main source of which is the attracted resources of the Bratsk reservoir.