Moscow Artesian Basin

an artesian basin in the center of the Eastern European Plain. Structurally it belongs to the southwestern part of the Moscow tectonic depression. The area of the basin is approximately 360, 000 sq km. The water-bearing beds are confined to a complex of calcareous terrigenous rock ranging from Early Cambrian to Quaternary in age and resting on a folded crystalline basement. In accord with the general subsidence of the basement from the southwest to the northeast, the thickness of the sedimentary deposits changes from 100–300 to 4, 000–4, 500 m. The Moscow artesian basin is characterized by the presence of three vertical zones that differ with respect to the particular features of the hydrodynamic and hydrochemical conditions.

The upper zone, or the zone of intensive water exchange (intensive underground drainage), is characterized by conditions conducive to the infiltration of atmospheric water, by the interaction of individual water-bearing complexes, and by a hydraulic connection of the underground water with surface watercourses and reservoirs. The conditions for the feeding, drainage, discharge, and formation of the underground water resources are closely linked to the particular features of the topography and climate, as well as to the draining action of the river network. This zone, which is about 250–300 m thick, contains mainly fresh water (up to 1 g/l) of the hydrocarbonate class.

Below the upper zone is a zone of restricted water exchange, where the movement of underground water has been greatly impeded because of the great depth, the slight influence of river drainage, and minor fissuring of the rock. The leaching of salts is impeded, and sulfates and chlorides predominate in the composition of the water. The water is subsaline or saline with a mineralization ranging from 5–10 to 50 g/l. The thickness of the zone is 300–400 m.

In the deepest regions of the Moscow artesian basin lies a zone of greatly reduced water exchange. The flow of the water and the processes of rock elutriation are negligible here, and brines have developed with a high concentration from 50 to 270 g/l and with sodium chloride as the principal salt. The thickness of the zone varies from 400–500 to 1, 600–2, 000 m in the most subsided portions of the basin.

The underground fresh waters of the basin have long been a source of water for Moscow and the entire central industrial region of the European USSR. The underground water in the Moscow artesian basin constitutes as much as 40 percent of the total water resources of the basin’s territory. About 15–20 percent of the water supply for the aquifers comes from atmospheric precipitation. The Carboniferous water-bearing complexes are most abundant; their waters are widely used for drinking and industrial purposes.

The saline waters and brines from the zones of reduced water exchange, confined predominantly to the Devonian and Permian deposits, are used for therapeutic and balneological purposes (Staraia Russa, Kashin). The slightly mineralized waters (4g/l ) from the Upper Devonian strata in the Moscow region are known as Moscow mineral water.