Hydrogeochemical characteristics of underground waters of Neogene sediments Paleo-Volga within the territory of Kazan

Abstract

Introduction: One of the sources of drinking water and industrial water supply in Kazan is the water-bearing Neogene terrigenous system. The aim of the study is to give hydrogeochemical characteristics to ground water of the Neogene system in terms of providing the city of Kazan with high-quality drinking water from protected underground sources. Methodology: The study used hydrochemical data from geological records and archives for the period from 1971 to 2017. The methods of mathematical statistics (basic, cluster, and factor analysis) allowed to differentiate natural and man-made components. GIS-modelling using the ArcGisMap package showed the spatial variability of the main components in the waters of the Neogene system at the turn of the 20th and 21st centuries. Results and discussion: 2 groups of components were distinguished in the studied water-bearing system: “natural” and “man-made”. The natural components include hydrocarbonates, magnesium, calcium, mineralisation, and total hardness. Man-made components are chlorides, total iron, sodium, and potassium. In the 21st century, there has been an increase in the anthropogenic impact on underground water wells of centralized water supply from the Neogene system, due to their long (40-50 years) service life. Conclusions: Hydrochemical characteristics of the water-bearing Neogene terrigenous system are estimated as being favourable, since nearly all key components do not exceed the limit values for the maximum permissible concentration (MPC) for drinking water. The high quality groundwater of the Volga paleovalleys allows us to consider them as being the most promising groundwater supply source in Kazan.