Volga river

The Volga River is a river in the European part of Russia, one of the largest rivers on Earth and the largest in Europe. One of the branches of the lower reaches of the Volga - the Kigach River - crosses the territory of Kazakhstan.

The Volga originates in the Valdai Upland (at an altitude of 229 m), flows into the Caspian Sea. The mouth lies at 28 m below sea level. The total drop is 256 m. The Volga is the world's largest river of internal flow, that is, it does not flow into the world ocean. The river system of the Volga basin includes 151 thousand watercourses (rivers, streams and temporary watercourses) with total length of 574 thousand km. The Volga takes about 200 tributaries. The left tributaries are more numerous and more numerous than the right. After Kamyshin, there are no significant tributaries. The Volga basin occupies about 1 / 3 of the European territory of Russia and extends from the Valdai and Central Russian uplands in the west to The Urals In the east. The main, feeding part of the catchment area of ​​the Volga, from the source to the cities of Nizhny Novgorod and Kazan, is located in the forest zone, the middle part of the basin to the cities of Samara and Saratov - in the forest-steppe zone, the lower part - in the steppe zone to Volgograd, and to the south - in the semidesert zone . The Volga is divided into 3 parts: the upper Volga - from the source to the mouth of the Oka, the middle Volga - from the confluence of the Oka to the mouth of the Kama and the lower Volga - from the confluence of the Kama to the mouth.

The main supply of the Volga is carried out by snow (60% annual runoff), groundwater (30%) and rain (10%) waters. The natural regime is characterized by a spring flood (April-June), low water content during the summer and winter meadows, and autumn rainfalls (October). Annual fluctuations of the Volga level before regulation reached Tver 11 m, below the Kama estuary - 15-17 m and Astrakhan - 3 m. With the construction of the reservoirs, the flow of the Volga is regulated, fluctuations in the level have sharply decreased. At the same time, waves of a height of up to 1,5 meters are formed in wide multi-kilometer reservoirs (eg, in Rybinsk, Kuybyshevsky) in inclement weather, to counteract which in the water area of ​​a number of Volga ports (eg Kazan), artificial breakwaters were built. In addition, due to the rise in the level of reservoirs along low-lying shores, wide and often shallow-water marshy estuaries and creeks were formed in a number of cities, and engineering protective structures were built in the form of dams, reserve pumps, etc.

Average annual water discharge at the Verkhnevolzhsky Bayslot 29 m³/ Sec, near the city of Tver - 182, near the city of Yaroslavl - 1 110, near the city of Nizhny Novgorod - 2 970, near the city of Samara - 7 720, near the city of Volgograd - 8 060 m³/ Sec. Below Volgograd, the river loses about 2% of its expenditure on evaporation. The maximum water flow in the period of high water in the past below the confluence of the Kama reached 67 000 m³/ Sec, while in Volgograd as a result of flooding on the floodplain did not exceed 52 000 m³/ Sec. In connection with the regulation of flow, the maximum outflows have drastically decreased, while summer and winter low-cost expenditures have increased significantly. The water balance of the Volga basin to Volgograd on average over a long period is: precipitation 662 mm, or 900 km³ Per year, river flow 187 mm, or 254 km³ Per year, evaporation 475 mm, or 646 km³ in year. Before the creation of reservoirs during the year, the Volga carried to the mouth about 25 million tons of sediments and 40-50 million tons of dissolved minerals. The water temperature of the Volga in the middle of summer (July) reaches 20-25 ° C. The Volga opens near Astrakhan in mid-March, in the 1-half of April, an autopsy takes place on the upper Volga and below Kamyshin, in the rest of the stretch - in mid-April. It freezes in the upper and middle reaches at the end of November, in the lower - at the beginning of December; Free of ice remains about 200 days, and near Astrakhan about 260 days. With the creation of reservoirs the thermal regime of the Volga has changed: on the upper tunnels the duration of the ice phenomena has increased, and on the lower ones it has become shorter.