Angara-Lena artesian basin

ANGARA-LENA ARTESIAN BASIN (RU: Ангаро-Ленский артезианский бассейн) is situated within the Asian part of the territory of the RSFSR and is confined to the southern protrusion of the Siberian platform. The area is approximately 520 thousand square kilometres. The major aquiferous complexes are: the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic and Jurassic ones, there have lesser significance the Cretaceous, Paleogene-Neogene and Quaternary ones.

All the complexes are formed mainly of the carbonatic and clastic rocks (the Cambrian one is also formed of the chemogenic sediments, the significant role in the composition of the Permo-Triassic one belongs to the trappous formations and accompanying pyroclastic formations). The Jurassic depositions form the Irkutskaya, Kanskaya, Murskaya, and the series of the smaller depressions, which are forming the small independent artesian basins. There are most aquiferous the sandstones and limestones, especially their karstic varieties, which are feeding the water springs with the yields of up to several hundred litres per second. The feeding of the underground waters of the basin proceeds on the account of the infiltration of the precipitation, absorption of the river waters (especially within the places of the development of the karst), condensation of the moisture from the air. The discharge of the underground waters is performed with the help of the hydrographic network and along the zones of the rupture dislocations of the deep aquifers.

There is characteristic for the basin the vertical zonality of the variation of the chemical composition of the underground waters. From the top to the bottom, there are distinguished the following zones: of the hydrocarbonatic magnesium-calcium and calcium-magnesium fresh waters; of the hydrocarbonatic sodium slightly brackish waters (0.2-0.7 grams per litre); of the sulfatic calcium brackish waters (1-5 grams per litre); of the chloridic sodium, calcium-sodium and calcium waters from the strong to the completely saturated brines (150-600 grams per litre); of the chloridic mainly calcium and sodium-calcium brines (from 290-350 to 500 grams per litre). The temperature of the deep underground waters of the basin is 20-50 degrees Celsius, rising to 75 degrees Celsius or more within the certain places. The usable reserves of the underground waters of the explored southern part of the basin (the area is 231.5 thousand square kilometres) is estimated at 209 cubic metres per second. Approximately 1% of these reserves are consumed for the water supply. The salty waters and brines of the southern part of the basin are used for the obtainment of the sodium chloride, there is also possible the extraction of the bromine, potassium, magnesium, and other elements.