Including the tap water many of us don’t think about the fact that it implies a valuable mineral. "Water in the twenty-first century will be more important than oil" is the title of the published report of UN experts, which stated that the already acute water shortage faced by many cities on the planet. The depths of the Leningrad region is rich in fresh water, but its stocks still exhaustible. Look at the underground pantries in our area. Finding water in the bowels, especially its composition and distribution is subject to the geological structure of the territory. In hydrogeological respect, the Leningrad region is located within three hydrogeologic structures:
1) Baltic fissure and fissure-vein waters, covering the Northern part of the Karelian isthmus and a small area in the North, Podporozhsky district;
2) Moscow basin pressure water reservoir located in the Eastern parts of the Tikhvin and Boksitogorsky areas;
3) Leningrad basin reservoir pressure water, occupies the rest of the field.
Underground waters contain dissolved complex ions and molecules of various salts, colloids mineral and organic origin, as well as gases. The amount of solids dissolved in water, total mineralization, which is usually expressed in grams per litre or cubic decimeter of water.
Fresh water has salinity up to 1 g/l, brackish — 1-3, 3-35 salt. Water with salinity greater than 35 g/l, i.e. more than the average salinity of sea water are brines. The lower boundary of the distribution of fresh groundwater in the Leningrad region is located at depths of 100-200 m, increasing up to 3000 meters or more at the sites where permeable rocks (elevated areas on the Karelian isthmus, the South-Western part of the region) and reduced to 0-50 m in the valley of the river Volkhov, and Neva Predportoviy the lowlands. With depth, the groundwater salinity increases, freshwater and brackish are replaced by deeper saline waters and brines.
Fresh water common in the upper part of geological section and are allocated in all the levels — from the crystalline basement rocks to Quaternary deposits. Near surface groundwater is widely developed safe water. They are confined to different types of rocks mainly of Quaternary age. Water intertill horizons typically of potable quality and have a salinity of 0.1-0.8 g/l; only in certain areas, they are observed mineralization from 1.0 to 3.0 g/L. underground waters Often contain elevated concentrations of iron up to 3-10 mg/l, and in the district of Polyustrovo — 20-45 mg/L. These aquifers is quite vaudevillian and are used for water supply. For example, in the Resort area of St.-Petersburg partially explored and used several deposits intertill waters (Youth, Zelenogorsk, Dunes, Solar, etc.). In the Northern part of the region Vendian water complex are widely used for drinking water supply of settlements of Roschino, Solar, Repino, etc. Is usually the groundwater consumption for drinking water bottling ("Rosinka", etc.), they are produced of artificial mineral water ("Borzhomi", "Essentuki") and a variety of drinks. To the South, on the territory of St. Petersburg and suburban areas, saline water is extracted for water supply and is also used for balneological purposes. Vendian groundwater complex is protected from surface contamination by a layer of kotlin clays up to 60 m and are, therefore, reliable source of drinking water.
Natural hydrogeological conditions of the Leningrad region favorable for the formation of various mineral waters, and suitable for use in a variety of ways. In accordance with applicable standards to include mineral water with salinity over 1 g/l or less mineralization, but containing biologically active components (bromine, iron, etc.). According to its application and impact on human mineral drinking waters are used for domestic drinking and washing, and Spa, used in the form of baths, showers and bathing. Among common drinking mineral waters chalybeate, chloride and sulphate. Chalybeate mineral waters are confined to the upper intertill the horizon and occur on the Karelian isthmus and in Saint Petersburg. Significant reserves of ferruginous water containing biologically active ferrous iron (up to 20-35 mg/l) is known in Vsevolozhsk (der. Korkino, village Yanino) and Luga districts. Chloride mineral water with salinity of 1 to 8 g/l are common in Vendian aquifer complex in most parts of the region. Sulfate mineral water of different cationic composition developed in Boksitogorsk, Volkhov and Kirishi districts where they are confined to the upper Devonian, Ordovician, and Cambrian-Ordovician sediments. Their mineralization does not exceed 3.5-4 g/l. Radon water encountered in the weathering crust of granites in the Karelian isthmus and the sandstones of the lower Ordovician along the Baltic Ladoga scarp. Chloride, sodium, bromine developed in the South region (Luga, Kirishi, Tosno district). In Vendian aquifer complex the bromine content reaches 90-95 mg/l Underground water is perhaps the only minerals whose reserves are replenished naturally as the operation field. However, groundwater is also the only mineral, varying in quality in short time intervals. Under natural conditions, groundwater quality depends on the nature of the interaction system: water — rock — air — living matter. Each component of this system varies in time, and this is reflected in the composition of the water. Groundwater quality is determined not only by natural factors, but also largely formed under the influence of various economic activities and conditions of operation of water.