Why did the Caspian Sea become a lake. Why the Caspian Sea cannot be called either a sea or a lake

The territory of Russia is washed by twelve seas belonging to the basins of three oceans. But one of these seas - the Caspian - is often called a lake, which sometimes confuses people who are poorly versed in geography.

Meanwhile, it is really more correct to call the Caspian a lake, not a sea. Why? Let's figure it out.

A bit of geography. Where is the Caspian Sea located?

Occupying an area that exceeds 370,000 square kilometers, the Caspian Sea stretches from north to south, dividing Europe and Asia with its water surface. Its coastline belongs to five different countries: Russia, Kazakhstan, Azerbaijan, Turkmenistan and Iran. Geographers conditionally divide its water area into three parts: Northern (25% of the area), Middle (36% of the area) and South Caspian (39% of the area), which differ in climate, geological setting and natural features. The coastline is mostly flat, indented by river channels, covered with vegetation, and in the northern part, where the Volga flows into the Caspian, it is also swampy.

The Caspian Sea has about 50 large and small islands, about a dozen bays and six large peninsulas. In addition to the Volga, about 130 rivers flow into it, and nine rivers form fairly wide and branched deltas. The annual drainage of the Volga is about 120 cubic kilometers. Together with other large rivers - the Terek, the Urals, the Emba and the Sulak - this accounts for up to 90% of the total annual runoff to the Caspian.

Why is the Caspian called a lake?

The main feature of any sea is the presence of straits connecting it with the ocean. The Caspian is a closed, or endorheic body of water, which receives river water, but does not connect with any ocean.


Its water contains a very small amount of salt compared to other seas (about 0.05%) and is considered slightly salty. Due to the lack of at least one strait connecting with the ocean, the Caspian is often called the largest lake in the world, since the lake is a completely closed reservoir, which is fed only by river water.

The waters of the Caspian Sea are not subject to international maritime laws, and its water area is divided among all countries that adjoin it, in proportion to the coastline.

Why is the Caspian called the sea?

Despite all of the above, most often in geography, as well as in international and domestic documents, the name “Caspian Sea” is used, and not “ Caspian lake". First of all, this is due to the size of the reservoir, which is much more typical for the sea than for the lake. Even, which is much smaller in area than the Caspian, locals often referred to as the sea. There are no other lakes in the world whose shores belong to five different countries at the same time.

In addition, attention should be paid to the structure of the bottom, which near the Caspian Sea has a pronounced oceanic type. Once the Caspian Sea, most likely, was connected with the Mediterranean, but tectonic processes and drying up separated it from the World Ocean. More than fifty islands are located in the Caspian Sea, and the area of ​​some of them is quite large, even by international standards they are considered large. All this makes it possible to call the Caspian a sea, not a lake.

origin of name

Why is this sea (or lake) called Caspian? The origin of any name is often associated with ancient history terrain. Different peoples who lived on the shores of the Caspian called it differently. More than seventy names of this reservoir have been preserved in history - it was called the Hyrcanian, Derbent, Sarai Sea, etc.


Iranians and Azerbaijanis still call it the Khazar Sea. It began to be called Caspian by the name of the ancient tribe of nomadic horse breeders who lived in the steppes adjacent to its coast - a large tribe of Caspians. It was they who gave the name to the largest lake on our planet - the Caspian Sea.

The Caspian Sea is located on the Eurasia continent. Surprisingly, the Caspian Sea with an area of ​​370 thousand square kilometers is actually the largest lake, since it has no connection with the ocean. Although it is difficult to call it a lake, because the composition of the water, flora and fauna are similar to those of the sea. The salinity of the water is close to oceanic (from 0.05% to 13%).

Photo: Seagulls on the shore of the Caspian Sea.

About 50 million years ago in the territory of Eastern Europe The Tethys Sea was located, which, drying up, was divided into several large reservoirs - the Caspian, Black and Mediterranean Seas.

Thanks to mineral waters and therapeutic mud near the Caspian Sea has a great recreational and health-improving potential. Therefore, there is an increase in the popularity of the coast of Turkmenistan, Iran, Azerbaijan and Russian Dagestan among tourists.

Especially popular is resort area in the Baku region, where popular resort in Amburan, as well as the area of ​​the village of Nardaran, sanatoriums in the villages of Zagulba and Bilgah. In the north of Azerbaijan, the resort in Nabran is gaining popularity.

Unfortunately, tourism in Turkmenistan is underdeveloped due to the isolation policy. And in Iran, Sharia law prohibits rest foreign tourists on the coast.

But if you decide to relax on the Caspian Lake, then you will like to walk in protected areas, you will see unusual floating islands, a variety of plants and animals that live in fresh and salt waters.

Here, throughout the year, a greater variety of ways to have a good time is offered. For example, you can go on boat cruises, go fishing or waterfowl hunting, or you can simply enjoy the healing waters, watching seals and various birds. The protected areas of the sea coast are very beautiful, for example, the Astrakhan International Biosphere Reserve and the Volga Delta with lotus fields.

A feature of the Caspian region is oriental flavor with a hookah and bewitching dances. Traditional music will delight your ears, and East Asian cuisine will satisfy your hunger.

See where the Caspian Sea is located on the world map.

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Video: Caspian Sea. Storm. 08.07.2012.

Caspian Sea

The Caspian Sea (Greek Káspion pélagos, Latin Caspium Mare), the world's largest enclosed body of water in the USSR (RSFSR, Kazakh SSR, Turkmen SSR, Azerbaijan SSR) and Iran. Often regarded as the greatest lake Earth, which is inaccurate, since in terms of its size, the nature of the processes and the history of the development of the sea, the sea. It received its name from the ancient tribes of the Caspians (See Caspians), who lived in the eastern part of the Caucasus. Other historical names - Hyrcanian, Khvalynsk (Khvalissk), Khazar - also by the names of the ancient peoples who lived on its shores.

Physico-geographical essay. General information. K. m. elongated from north to south by almost 1200 km, average width 320 km, the length of the coastline is about 7 thousand km. km(Of which more than 6,000 km within the USSR). The area is about 371 thousand sq. km 2; level at 28.5 m below the level of the World Ocean (1969). Maximum depth 1025 m. In 1929, before a significant decrease in the level of the K. m., its area was 422 thousand square meters. km 2. The largest bays are: in the north - Kizlyarsky, Komsomolets; in the east - Mangyshlaksky, Kenderli, Kazakhsky, Kara-Bogaz-Gol, Krasnovodsky; in the west - Agrakhansky, Baku Bay; in the south - shallow lagoons. There are up to 50 islands, mostly small ones (the total area is about 350 km 2), the most significant are Kulaly, Tyuleniy, Chechen, Artem, Zhiloy, Ogurchinsky.

The most significant rivers flow into the northern part of the sea - the Volga, Emba, Ural, Terek, the total annual flow of which is about 88% of the total river water flow into the Caspian. On the western coast, the large rivers Sulak, Samur, Kura and a number of smaller ones (about 7% of the flow) flow into it. The remaining 5% of the runoff is provided by the rivers of the Iranian coast (Gorgan, Heraz, Sefidrud). On the east coast, including the coast of Kara-Bogaz-Gol, there is not a single permanent watercourse.

Shores. The shores of the northern part of the Caspian are low-lying and very sloping, characterized by a wide development of droughts formed as a result of surge phenomena; deltaic shores are also developed here (deltas of the Volga, Ural, Terek). In general, the coasts of the northern part are intensively growing, which is facilitated by a drop in sea level, the rapid growth of deltas, and an abundant supply of terrigenous material. The western shores of the Caspian Sea are also mostly accumulative (numerous bays and spits), and some areas on the coasts of Dagestan and the Absheron Peninsula are abrasion. On the eastern coast of the sea, abrasion shores are dominated, worked out in limestones that make up the adjacent semi-desert and desert plateaus. There are also accumulative forms: the Karabogaz bay separating from the sea the largest bay of the Caspian - Kara-Bogaz-Gol, the Krasnovodskaya and Kenderli spits. To the south of the Krasnovodsk Peninsula, accumulative shores predominate.

Relief. According to the nature of the relief and hydrological features, the Caspian Sea is usually subdivided into the Northern Caspian, the Middle Caspian, and the Southern Caspian. Northern Caspian (area about 80 thousand sq. km 2) - the shallowest part of the sea with depths 4-8 m. The bottom relief is a slightly wavy accumulative plain with a series of banks and accumulative islands, the so-called Mangyshlak threshold, which separates the Northern Caspian from the Middle. Within the Middle Caspian (an area of ​​about 138 thousand sq. km 2) stand out: Derbent depression ( maximum depth 788 m), shelf and continental slope, complicated by underwater landslides and canyons; on the northern, rather gentle slope, relics of ancient river valleys were found. In the south, the basin of the Middle Caspian is separated from the basin of the South Caspian by the Apsheron threshold, on which a number of banks and islands are located. The basin of the South Caspian (the greatest depth is 1025 m), which is about 1/3 of the area of ​​the sea, has a narrow shelf off the western and southern (Iranian) coasts, and the shelf is much wider off the eastern coast. The bottom of the depression is a flat abyssal plain. In the northern part of the basin, there are several underwater ridges with northwestern and southeastern strikes.

Geological structure and minerals. The northern part of the Caspian sea is the margin of the Caspian syneclise of the East European platform; The Mangyshlak threshold is structurally connected with the Hercynian buried shaft of Karpinsky on the western coast of the sea and with the mountains of Mangyshlak on the east. The bottom of the Middle Caspian has a heterogeneous structure. Its eastern part is a submerged section of the epihercynian Turan platform; The Derbent depression, as well as the western parts of the shelf and the continental slope, are the marginal foredeep of the Greater Caucasus geosyncline. The Apsheron Sill corresponds to one of the branches of the newest structures formed on the subsidence of the folded formations of the Greater Caucasus and connecting them with the folded structures of the Kopetdag. The Southern Caspian is characterized by the suboceanic structure of the earth's crust; there is no granite layer here. Under the sedimentary layer up to 25 km(which obviously indicates the great antiquity of the South Caspian depression) there is a basalt layer up to 15 km.

Up to the Upper Miocene, the Caspian sea ​​pool in its geological history was closely associated with the Black Sea. After the Upper Miocene folding, this connection was interrupted, and the K. m. turned into a closed reservoir. Communication with the ocean resumed in the Upper Pliocene, in the Akchagyl age. In the Anthropogen, in connection with the alternation of glacial and postglacial epochs on the East European Plain, the Caspian Sea repeatedly experienced transgressions (Baku, Khazar, Khvalyn) and regressions, traces of which are preserved in the form of terraces on the sea coast and in the stratigraphy of the ancient Caspian deposits.

On the shelf, terrigenous-shell sands, shells, and oolitic sands are common; deep-water areas of the bottom are covered with silty and silty sediments with a high content of calcium carbonate. In some areas of the bottom, Neogene bedrocks are exposed. At the bottom of the sea there are rich deposits of oil and gas. Oil and gas are the Apsheron threshold, the Dagestan and Turkmen regions of the sea. Promising for oil and gas are the areas of the seabed adjacent to Mangyshlak, as well as the Mangyshlak threshold. The Kara-Bogaz-Gol Bay is the largest deposit of chemical raw materials (in particular, mirabilite).

Climate. The main baric centers that determine atmospheric circulation in the area of ​​the Caspian Sea are the spur of the Asian maximum in winter and the spurs of the Azores maximum and South Asian minimum in summer. Characteristic features of the climate are: significant continentality, the predominance of anticyclonic weather conditions, dry winds, severe frosty winters (especially in the northern part), sharp temperature changes throughout the year, poverty in precipitation (excluding the southwestern part of the reservoir). At atmospheric fronts, cyclonic activity is developing, which is also an important element of climate and weather in the Caspian. In the northern and middle parts of the Caspian Sea, easterly winds prevail from October to April, and northwestern winds prevail from May to September; in the southern part of the sea, the monsoon character of the winds is most pronounced. The region of the Apsheron Peninsula (Baku north blowing mainly in autumn), the eastern coast of the middle part and the northwestern region of the northern part are distinguished by the strongest winds; storms are frequent here, in which the wind speed reaches more than 24 m/sec.

The average long-term air temperature of the warm months (July-August) over the entire sea is 24-26 °C, the absolute maximum (up to 44 °C) is noted on the east coast. In the winter months, the temperature varies from -10 °C in the north to 12 °C in the south. An average of 200 mm precipitation per year, on the west coast - up to 400 mm, in the arid east - 90-100 mm, in the subtropical southwestern part of the coast - before 1700 mm. Evaporation from most of the sea surface is very high - up to 1000 mm in year; in the eastern part of the South Caspian and in the area of ​​the Apsheron Peninsula - up to 1400 mm in year.

hydrological regime. The cyclonic circulation of waters dominates in the sea, mainly due to river runoff and prevailing winds. Masses of water move from north to south along West Bank sea ​​to the Apsheron Peninsula, where the current splits: one branch continues along the western coast, the other crosses the K. m. in the area of ​​​​the Apsheron threshold and at east coast connects with waters moving northward along the eastern coast from the southern Caspian. In the South Caspian, cyclonic circulation is also observed, but less clearly expressed, and between Baku and the mouth of the river. Chickens complicated by local anticyclone circulation. Unstable wind currents of various directions prevail in the Northern Caspian. Their speed is usually 10-15 cm/sec, with strong winds coinciding with the direction of the currents, the speed can reach 30-40 and even 100 cm/sec. Frequent repetition of moderate and strong winds causes big number days of great excitement. Maximum observed wave height up to 11 m- in the area of ​​the Apsheron threshold. The water temperature in summer on the surface averages 24-26°C, in the south - up to 29°C, in the Krasnovodsk Bay - up to 32°C. Near the eastern shores in July and August the temperature sometimes drops to 10-12 °C. This phenomenon is associated with the driving effect of winds and the rise of deep waters. In winter, there are significant temperature contrasts: negative temperatures (down to -0.5°C) in the north, 3–7°C in the Middle Caspian, and 8–10°C in the South. The northern part of the sea usually freezes for 2-3 months., the ice thickness reaches 2 m. In the Middle Caspian, in severe winters, individual shallow bays freeze. There are frequent cases of intense breaking of ice by the wind and their drift from the North Caspian to the south along the western coast. In some years floating ice reach the area of ​​the Absheron Peninsula and are capable of causing significant damage to hydraulic structures in the sea.

The average salinity of the waters is 12.7-12.8 ‰, the maximum (not counting the Kara-Bogaz-Gol Bay) near the eastern shores is up to 13.2 ‰, the minimum is in the northwest. - 1-2 ‰. Fluctuations in salinity over the area of ​​the sea, along the vertical, and over time are insignificant, and only in the north are they more noticeable in connection with fluctuations in the flow of the Volga. The composition of salts differs from the usual oceanic salts in a high content of sulfates, calcium and magnesium carbonates and, accordingly, a lower content of chlorides, which is due to the influence of river runoff.

Vertical mixing of waters in winter covers the entire water column in the Northern Caspian and layer 200-300 m in deep-water areas, in summer and autumn it is limited to the upper layer 15-30 m. In these seasons, at the lower boundary of the upper well-heated and mixed layer (15-30 m) an intense layer of temperature jump (several degrees per meter) is formed, which prevents the spread of heat into the deep layers of the sea.

Level fluctuations. Short-term non-periodic fluctuations in the level of K. m. m or downgrade to 2 m. Seishi are observed with a period of 10 min to 12 h with amplitude up to 0.7 m. There are slight seasonal fluctuations in the level (about 30 cm).

The level of K. m. is subject to significant long-term and secular fluctuations, determined mainly by changes in its water balance. According to geological, archaeological, historical and geomorphological data, it has been established that a high level of K. m. (up to a mark of 22 m) was noted 4-6 thousand years ago, at the beginning of AD. e. and at the beginning of the 19th century. (New Caspian transgression). It is also known that in the 7-11 centuries. n. e. was low (perhaps 2-4 m below modern). The last major decline in the level occurred since 1929 (when the level was around 26 m) until 1956-57. Now the level fluctuates within several cm around 28.5 m. In addition to climatic changes, which led to a decrease in river runoff in the Caspian Sea and an increase in evaporation from its surface, the reasons for the last drop in the level were also hydraulic engineering construction on the Volga (creation of large artificial reservoirs) and the consumption of river waters for irrigating arid lands and for production needs. The runoff of the K. m. in the Kara-Bogaz-Gol Bay also negatively affects the water balance, the level of which is 4 m below the level of the Caspian Sea. In general, the components of the water balance for 1970: income - precipitation 66.8 km 3, river flow 266.4 km 3, underground inflow 5 km 3, consumption - evaporation 357.3 km 3, drain to Kara-Bogaz-Gol 4 km 3 , sea water intake 1 km 3 . The excess of the expenditure over the inflow of water causes an average annual decrease in the level (for the period 1966-67) by 7 cm. To prevent a further drop in sea level (by 2000, a decrease of 2 m) a number of measures are being developed. There is a project to divert the flow of the northern rivers - Vychegda and Pechora - into the Volga basin, which will give the Volga and K. m. about 32 km 3 water per year; a project was developed (1972) to regulate the flow of Caspian waters into the Kara-Bogaz-Gol Bay.

The flora and fauna of the K. m. are rather poor in species composition, but significant in biomass. More than 500 species of plants and 854 species of fish and animals, diverse in their origin, live in the Caspian Sea. Blue-green and diatom (rhizosolinae, etc.) algae predominate among the plants in the sea. Among recent invaders there are many red and brown algae. Of the flowering plants, zostera and ruppia are the most common. Chara algae provide the largest biomass (up to 30 kg for 1 m 3 bottoms). By origin, the fauna is mainly of the Neogene age, which has experienced great changes due to frequent and significant fluctuations in salinity. This group includes fish - sturgeons, herring, sprats, gobies, gobies, from mollusks - zebra mussels and cockles, from other invertebrates - gammarids, polychaetes, sponges, one type of jellyfish. In addition, 15 species of invaders from the Arctic and Mediterranean basins live here. A noticeable group is represented by organisms of freshwater origin (from fish - pike perch). In general, a high degree of endemism is characteristic. Some organisms have migrated to the K. m. quite recently or as a result of entering on the bottoms sea ​​vessels(mainly various fouling agents, for example, mytilaster, rhizosalina algae, balanus, and crabs), or by conscious acclimatization by humans (for example, from fish - mullet, from invertebrates - nereis, syndesmia).

Research History. Documentary evidence of the acquaintance of Russians with the K. m. and their voyages on it dates back to the 9th-10th centuries. (Arabic, Armenian, Iranian ancient manuscripts). Regular exploration of the Caspian Sea was begun by Peter I, on whose initiative an expedition was organized in 1714-15 under the leadership of A. Bekovich-Cherkassky, who explored, in particular, the eastern coast of the Caspian Sea. In the 20s. 18th century hydrographic studies of the sea were started by I.F. Soymonov; in the second half of the 18th century. they were continued by I. V. Tokmachev, M. I. Voinovich, at the beginning of the 19th century. - Kolodkin, who for the first time performed instrumental compass survey of the coast. In the middle of the 19th century a detailed instrumental hydrographic survey of the rock was carried out under the direction of N. A. Ivashintsev. The maps created from these surveys served as the basis for subsequent editions. nautical charts in the Caspian until the 30s. 20th century In the study of natural conditions K. m. in the 19th century. scientists made a great contribution - P. S. Pallas, S. G. Gmelin, G. S. Karelin, K. M. Baer, ​​G. V. Abikh, O. A. Grim, N. I. Andrusov, I. B. . Spindler. In 1897 the Astrakhan Research Station (now the Caspian Institute of Fisheries) was founded. In 1866, 1904, 1912-13, 1914-15 under the leadership of N. M. Knipovich, expeditionary research was carried out on the hydrology and hydrobiology of the Caspian Sea. These works were continued after 1917 by the Caspian Expedition created under the Academy of Sciences of the USSR, also led by Knipovich. In the first decades after the October Revolution, an outstanding role in the study of the geological structure and oil content of the Apsheron Peninsula and the geological history of the K. m. was played by the research of owls. geologists I. M. Gubkin, D. V. and V. D. Golubyatnikov, P. A. Pravoslavlev, V. P. Baturin, S. A. Kovalevsky. B. A. Appolov, V. V. Valedinsky, K. P. Voskresensky, and L. S. Berg made a significant contribution to the study of the water balance and fluctuations in the level of the sea level at that time. After the Great Patriotic War of 1941–45, systematic, versatile research began on the sea, aimed at studying the hydrometeorological regime, the biological conditions, and the geological structure of the sea (Moscow State University, the Institute of Geography of the Academy of Sciences of the Azerbaijan SSR, the State Oceanographic Institute, and the observatory of the hydrometeorological service. institutes of geology and development of fossil fuels (IGIRGI) and physics of the Earth of the Academy of Sciences of the USSR, the Laboratory of Aeromethods and the All-Russian Research Institute of Geophysics of the Ministry of Geology of the USSR, the Caspian Institute of Sturgeon Fisheries and other scientific institutions of the Republican Academy of Sciences and ministries].

Economic and geographical outline. The Caspian Sea has long been famous as an area for the production of valuable varieties of fish, especially sturgeon (82% of the world catch), herring, and freshwater fish (bream, pike perch, roach, and carp). As a result of the fall in sea level (which resulted in the disappearance of valuable spawning grounds), the regulation of the flow of the Volga, Kura and Araks rivers, which worsened the breeding conditions for anadromous and semi-anadromous fish, etc. the number and catch of primarily valuable varieties of fish (herring, sturgeon) have declined sharply. In 1936, the gross catch of fish was about 500,000 tonnes. T, in 1956 - 461 thousand. T(respectively, the catch of sturgeon - 21.5 and 15.0, roach - 197 and 18, pike perch - 55 and 8.4 thousand tons). T). A relatively small reduction in the gross catch is due to a sharp increase in the production of low-value fish, mainly kilka. Due to the decrease in the number of sturgeons, work is underway to breed and restore valuable fish species.

In 1924, oil production began for the first time in Ilyich Bay (Baku region), but production increased especially after the Great Patriotic War of 1941-45. Oil is extracted offshore from overpasses (Oil Rocks) and artificial islands. The main districts are the Apsheron, Sangachal west coast, Chelekensky - at the eastern. Offshore oil fields provide more than 50% of all oil produced in the Azerbaijan SSR. Of great economic importance is the extraction of sodium sulfate, mirabilite and epsomite in the Kara-Bogaz-Gol region.

The ever-increasing need for fresh water caused the appearance of desalination plants on the K. m. sea ​​water; the largest of them (by receiving fresh water for industrial and domestic needs in the adjacent desert and semi-desert regions) are being built (1972) in the years. Shevchenko and Krasnovodsk.

The metropolitan area is of great transport importance both for internal transportation and for external communications. The main cargoes transported across the Caspian are oil, timber, grain, cotton, rice, sulfate. Major ports- Astrakhan, Baku, Makhachkala, Krasnovodsk, Shevchenko - are also connected by regular flights passenger ships. Sea railways run between Baku and Krasnovodsk. ferries. A ferry service between Makhachkala and Shevchenko is being designed (1972). In Iran, the main ports are Pahlavi and Bandar Shah.

Lit.: Fluctuations in the level of the Caspian Sea, M., 1956; Fedorov P.V., Stratigraphy of Quaternary deposits and the history of the development of the Caspian Sea, M., 1957; Geological structure of the underwater slope of the Caspian Sea, M., 1962; Materials of the All-Union Conference on the Problem of the Caspian Sea, Baku, 1963; Zenkevich L. A., Biology of the Seas of the USSR, M., 1963; Leontiev O. K., Khalilov A. I., natural conditions formation of the shores of the Caspian Sea, Baku, 1965; Pakhomova A. S., Zatuchnaya B. M., Hydrochemistry of the Caspian Sea, Leningrad, 1966; Geology of oil and gas fields of Azerbaijan, M., 1966; Caspian Sea, M., 1969; Complex studies of the Caspian Sea. Sat. st., c. 1, M., 1970; Gul K. K., Lappalainen T. N., Polushkin V. A., Caspian Sea, Moscow, 1970; Gul K. K., Zhilo P. V., Zhirnov V. M., Bibliographic annotated guide to the Caspian Sea. Baku, 1970.

K. K. Gul, O. K. Leontiev.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

Synonyms:

See what the "Caspian Sea" is in other dictionaries:

Drainage, washes the shores of Russia (Dagestan, Kalmykia, Astrakhan region) and Azerbaijan, Iran, Kazakhstan, Turkmenistan. The earliest mention of the Caspian Sea is found in Assyrian. cuneiform inscriptions (VIII VII centuries BC), where it ... ... Geographic Encyclopedia

CASPIAN SEA, the world's largest endorheic lake. The area is 376 thousand km2. Lies 27.9 m below sea level (1986). From 1929 to 1977 there was a drop in the level, from 1978 a rise began. In the North Caspian the depth is 5-8 m, in the Middle Caspian up to 788 m... Modern Encyclopedia

Caspian Sea - the largest lake on Earth, drainless, located at the junction of Europe and Asia, called the sea because of its size, and also because its bed is composed of oceanic-type earth's crust. The water in the Caspian is salty - from 0.05 ‰ near the mouth of the Volga to 11-13 ‰ in the southeast. The water level is subject to fluctuations, according to 2009 data it was 27.16 m below sea level. The area of ​​the Caspian Sea is currently approximately 371,000 km², the maximum depth is 1025 m.

Geographical position

The Caspian Sea is located at the junction of two parts of the Eurasian continent - Europe and Asia. The length of the Caspian Sea from north to south is approximately 1200 kilometers (36°34 "-47°13" N), from west to east - from 195 to 435 kilometers, on average 310-320 kilometers (46°-56° v. d.). The Caspian Sea is conditionally divided according to physical and geographical conditions into 3 parts - the Northern Caspian, the Middle Caspian and the Southern Caspian. The conditional border between the North and Middle Caspian runs along the line of about. Chechnya - Cape Tyub-Karagansky, between the Middle and South Caspian - along the line of about. Residential - Cape Gan-Gulu. The area of ​​the Northern, Middle and Southern Caspian is 25, 36, 39 percent respectively.

The length of the coastline of the Caspian Sea is estimated at about 6500-6700 kilometers, with islands - up to 7000 kilometers. The shores of the Caspian Sea in most of its territory are low-lying and smooth. In the northern part, the coastline is indented by water channels and islands of the Volga and Ural deltas, the shores are low and swampy, and the water surface is covered with thickets in many places. The east coast is dominated by limestone shores adjacent to semi-deserts and deserts. The most winding coasts are on the western coast near the Apsheron Peninsula and on the eastern coast near the Kazakh Gulf and Kara-Bogaz-Gol. The territory adjacent to the Caspian Sea is called the Caspian Sea.

Peninsulas of the Caspian Sea

Large peninsulas of the Caspian Sea:

• Agrakhan Peninsula
• The Absheron Peninsula, located on the western coast of the Caspian Sea in the territory of Azerbaijan, at the northeastern end of the Greater Caucasus, the cities of Baku and Sumgayit are located on its territory
• Buzachi
• Mangyshlak is located on the eastern coast of the Caspian Sea, on the territory of Kazakhstan, on its territory is the city of Aktau
• Miankale
• Tyub-Karagan

Islands of the Caspian Sea

There are about 50 large and medium-sized islands in the Caspian Sea with a total area of ​​approximately 350 square kilometers. The largest islands:

• Ashur-Ada
• Garasu
• Boyuk Zira
• Zyanbil
• Cure Dashi
• Hara Zira
• Ogurchinsky
• Sengi-Mugan
• Seals
• Seal Islands
• Chechen
• Chygyl

Bays of the Caspian Sea

Large bays of the Caspian Sea:

• Agrakhan bay
• Kizlyar Bay
• Dead Kultuk (former Komsomolets, former Tsesarevich Bay)
• Kaydak
• Mangyshlak
• Kazakh
• Kenderly
• Turkmenbashi (bay) (former Krasnovodsk)
• Turkmen (bay)
• Gyzylagach (former bay named after Kirov)
• Astrakhan (bay)
• Hasan-kuli
• Gyzlar
• Hyrcanus (former Astarabad)
• Anzali (former Pahlavi)
• Kara-Bogaz-Gol

Rivers flowing into the Caspian Sea- 130 rivers flow into the Caspian Sea, of which 9 rivers have a mouth in the form of a delta. The major rivers flowing into the Caspian Sea are the Volga, Terek, Sulak, Samur (Russia), Ural, Emba (Kazakhstan), Kura (Azerbaijan), Atrek (Turkmenistan), Sefidrud (Iran) and others. The largest river flowing into the Caspian Sea is the Volga, its average annual runoff is 215-224 cubic kilometers. The Volga, Ural, Terek, Sulak and Emba provide up to 88-90% of the annual runoff to the Caspian Sea.

Physiography

Area, depth, volume of water- The area and volume of water in the Caspian Sea varies significantly depending on fluctuations in water levels. At a water level of -26.75 m, the area is approximately 371,000 square kilometers, the volume of water is 78,648 cubic kilometers, which is approximately 44% of the world's lake water reserves. The maximum depth of the Caspian Sea is in the South Caspian depression, 1025 meters from its surface level. In terms of maximum depth, the Caspian Sea is second only to Baikal (1620 m) and Tanganyika (1435 m). The average depth of the Caspian Sea, calculated from the bathygraphic curve, is 208 meters. At the same time, the northern part of the Caspian Sea is shallow, its maximum depth does not exceed 25 meters, and the average depth is 4 meters.

Water level fluctuations- The water level in the Caspian Sea is subject to significant fluctuations. According to modern science, over the past three thousand years, the magnitude of the change in the water level of the Caspian Sea has reached 15 meters. According to archeology and written sources, a high level of the Caspian Sea is recorded at the beginning of the 14th century. Instrumental measurement of the level of the Caspian Sea and systematic observations of its fluctuations have been carried out since 1837, during this time the highest water level was recorded in 1882 (−25.2 m), the lowest - in 1977 (−29.0 m), from In 1978, the water level rose and in 1995 it reached -26.7 m, since 1996 there has been a downward trend again. Scientists associate the causes of changes in the water level of the Caspian Sea with climatic, geological and anthropogenic factors. But in 2001, the sea level began to rise again, and reached -26.3 m.

Water temperature- water temperature is subject to significant latitudinal changes, most pronounced in winter, when the temperature changes from 0-0.5 °C at the ice edge in the north of the sea to 10-11 °C in the south, that is, the water temperature difference is about 10 ° C. For shallow water areas with depths less than 25 m, the annual amplitude can reach 25-26 °C. On average, the water temperature near the western coast is 1-2 °C higher than that of the eastern coast, and in the open sea the water temperature is 2-4 °C higher than near the coasts.

Water composition- the salt composition of the waters of the closed Caspian Sea differs from that of the ocean. There are significant differences in the ratios of the concentrations of salt-forming ions, especially for the waters of areas under the direct influence of continental runoff. The process of metamorphization of sea waters under the influence of continental runoff leads to a decrease in the relative content of chlorides in the total amount of salts in sea waters, an increase in the relative amount of carbonates, sulfates, and calcium, which are the main components in the chemical composition of river waters. The most conservative ions are potassium, sodium, chloride and magnesium. The least conservative are calcium and bicarbonate ion. In the Caspian Sea, the content of calcium and magnesium cations is almost two times higher than in the Sea of ​​Azov, and sulfate anion is three times higher.

Bottom relief- the relief of the northern part of the Caspian Sea is a shallow undulating plain with banks and accumulative islands, the average depth of the Northern Caspian is 4-8 meters, the maximum does not exceed 25 meters. The Mangyshlak threshold separates the Northern Caspian from the Middle. The Middle Caspian is quite deep, the depth of water in the Derbent depression reaches 788 meters. The Apsheron threshold separates the Middle and South Caspian. The South Caspian is considered deep water, the depth of water in the South Caspian depression reaches 1025 meters from the surface of the Caspian Sea. Shell sands are widespread on the Caspian shelf, deep-water areas are covered with silty sediments, and in some areas there is an outcrop of bedrock.

Climate- The climate of the Caspian Sea is continental in the northern part, temperate in the middle part and subtropical in the southern part. In winter average monthly temperature air varies from -8…-10 in the northern part to +8…+10 in the southern part, in summer - from +24…+25 in the northern part to +26…+27 in the southern part. The maximum temperature of +44 degrees was recorded on the east coast. The average annual rainfall is 200 millimeters, ranging from 90-100 millimeters in the arid eastern part to 1,700 millimeters off the southwestern subtropical coast. Evaporation of water from the surface of the Caspian Sea is about 1000 millimeters per year, the most intense evaporation in the area of ​​the Absheron Peninsula and in the eastern part of the South Caspian is up to 1400 millimeters per year. The average annual wind speed is 3-7 meters per second, the wind rose is dominated by northern winds. In the autumn and winter months, the winds increase, the wind speed often reaches 35-40 meters per second. The most windy areas are the Apsheron Peninsula, the environs of Makhachkala and Derbent, where the highest wave 11 meters high was also recorded.

currents- The circulation of waters in the Caspian Sea is connected with the runoff and winds. Since most of the water flow falls on the Northern Caspian, northern currents predominate. An intense northern current carries water from the Northern Caspian along the western coast to the Absheron Peninsula, where the current is divided into two branches, one of which moves further along the western coast, the other goes to the Eastern Caspian.

Economic development of the Caspian Sea

Oil and gas-Many oil and gas fields are being developed in the Caspian Sea. The proven oil resources in the Caspian Sea are about 10 billion tons, the total resources of oil and gas condensate are estimated at 18-20 billion tons. Oil production in the Caspian Sea began in 1820, when the first oil well was drilled on the Absheron shelf near Baku. In the second half of the 19th century, oil production began on an industrial scale on the Absheron Peninsula, and then on other territories. In 1949, Oil Rocks for the first time began to extract oil from the bottom of the Caspian Sea. So, on August 24 of this year, the team of Mikhail Kaverochkin started drilling a well, which on November 7 of the same year gave the long-awaited oil. In addition to oil and gas production, salt, limestone, stone, sand, and clay are also mined on the coast of the Caspian Sea and the Caspian shelf.

Shipping- Shipping is developed in the Caspian Sea. On the Caspian Sea ferry crossings, in particular, Baku - Turkmenbashi, Baku - Aktau, Makhachkala - Aktau. The Caspian Sea has a navigable connection with Sea of ​​Azov through the rivers Volga, Don and the Volga-Don Canal.

Fishing and seafood-fishing (sturgeon, bream, carp, pike perch, sprat), caviar production, as well as seal fishing. More than 90 percent of the world's sturgeon catch is carried out in the Caspian Sea. In addition to industrial production, illegal production of sturgeon and their caviar flourishes in the Caspian Sea.

Legal status of the Caspian Sea- after the collapse of the USSR, the division of the Caspian Sea has long been and still remains the subject of unsettled disagreements related to the division of the resources of the Caspian shelf - oil and gas, as well as biological resources. For a long time, negotiations were going on between the Caspian states on the status of the Caspian Sea - Azerbaijan, Kazakhstan and Turkmenistan insisted on dividing the Caspian along the median line, Iran - on dividing the Caspian along one fifth between all the Caspian states. The current legal regime of the Caspian is established by the Soviet-Iranian treaties of 1921 and 1940. These treaties provide for freedom of navigation throughout the sea, freedom of fishing, with the exception of ten-mile national fishing zones, and a ban on navigation in its waters of ships flying the flag of non-Caspian states. Negotiations on the legal status of the Caspian are currently ongoing.

V. N. MIKHAILOV

The Caspian Sea is the largest drainless lake on the planet. This body of water is called the sea for its huge size, brackish water and sea-like regime. The level of the Caspian Sea-lake lies much lower than the level of the World Ocean. At the beginning of 2000, he had a mark of about - 27 abs. m. At this level, the area of ​​the Caspian Sea is ~ 393 thousand km2 and the volume of water is 78,600 km3. The average and maximum depths are 208 and 1025 m, respectively.

The Caspian Sea is elongated from south to north (Fig. 1). The Caspian washes the shores of Russia, Kazakhstan, Turkmenistan, Azerbaijan and Iran. The reservoir is rich in fish, its bottom and banks are rich in oil and gas. The Caspian Sea is quite well studied, but many mysteries remain in its regime. The most characteristic feature of the reservoir is the instability of the level with sharp drops and rises. The last rise in the level of the Caspian took place before our eyes from 1978 to 1995. It gave rise to many rumors and speculation. Numerous publications appeared in the press, which spoke about catastrophic floods and ecological catastrophe. It was often written that the rise in the level of the Caspian Sea led to the flooding of almost the entire Volga delta. What is true in the statements made? What is the reason for such behavior of the Caspian Sea?

WHAT HAPPENED TO THE CASPIAN IN THE 20TH CENTURY

Systematic observations over the level of the Caspian Sea were started in 1837. In the second half of the 19th century, the average annual values ​​of the Caspian Sea level were in the range of marks from -26 to -25.5 abs. m and showed a slight downward trend. This trend continued into the 20th century (Fig. 2). In the period from 1929 to 1941, the sea level dropped sharply (by almost 2 m - from - 25.88 to - 27.84 abs. m). In subsequent years, the level continued to fall and, having decreased by approximately 1.2 m, reached in 1977 the lowest mark for the observation period - 29.01 abs. m. Then the sea level began to rise rapidly and, having risen by 2.35 m by 1995, reached a mark of 26.66 abs. m. In the next four years, the average sea level decreased by almost 30 cm. Its average marks were 26.80 in 1996, 26.95 in 1997, 26.94 in 1998 and 27.00 abs. m in 1999.

The decrease in sea level in the years 1930-1970 led to the shallowing of coastal waters, the extension of the coastline towards the sea, and the formation of wide beaches. The latter was perhaps the only positive consequence of the level drop. There were many more negative consequences. With a decrease in the level, the areas of forage land for fish stocks in the northern Caspian have decreased. The shallow estuarine coast of the Volga began to quickly overgrow with aquatic vegetation, which worsened the conditions for the passage of fish to spawn in the Volga. Catches of fish, especially valuable species such as sturgeon and sterlet, have sharply decreased. Shipping began to suffer damage due to the fact that the depths in the approach channels decreased, especially near the Volga delta.

The rise in the level from 1978 to 1995 was not only unexpected, but also led to even greater negative consequences. After all, both the economy and the population of coastal areas have already adapted to a low level.

Many sectors of the economy began to suffer damage. Significant territories turned out to be in the zone of flooding and flooding, especially in the northern (flat) part of Dagestan, in Kalmykia and the Astrakhan region. The cities of Derbent, Kaspiysk, Makhachkala, Sulak, Caspian (Lagan) and dozens of other smaller settlements suffered from the level rise. Significant areas of agricultural land have been flooded and flooded. Roads and power lines, engineering structures of industrial enterprises and public utilities are being destroyed. A threatening situation has developed with fish-breeding enterprises. Abrasion processes in the coastal zone and the effect of seawater surges have intensified. In recent years, the flora and fauna of the seashore and the coastal zone of the Volga delta suffered significant damage.

In connection with the increase in depth in the shallow waters of the Northern Caspian and the reduction in the areas occupied in these places by aquatic vegetation, the conditions for the reproduction of stocks of anadromous and semi-anadromous fish and the conditions for their migration to the delta for spawning have somewhat improved. However, the predominance of negative consequences from the rising sea level made us speak of an ecological catastrophe. The development of measures to protect national economic objects and settlements from the advancing sea began.

HOW UNUSUAL IS CURRENT CASPIAN BEHAVIOR?

Research into the life history of the Caspian Sea can help answer this question. Of course, there are no data from direct observations of the past regime of the Caspian Sea, but there are archaeological, cartographic and other evidence for historical time and the results of paleogeographic studies covering a longer period.

It is proved that during the Pleistocene (the last 700-500 thousand years) the level of the Caspian Sea underwent large-scale fluctuations in the range of about 200 m: from -140 to + 50 abs. m. In this period of time in the history of the Caspian, four stages are distinguished: Baku, Khazar, Khvalyn and New Caspian (Fig. 3). Each stage included several transgressions and regressions. The Baku transgression occurred 400-500 thousand years ago, the sea level rose to 5 abs. m. During the Khazar stage, there were two transgressions: the early Khazar (250-300 thousand years ago, the maximum level is 10 abs. m) and the late Khazar (100-200 thousand years ago, the highest level is 15 abs. m). The Khvalyn stage in the history of the Caspian included two transgressions: the largest for the Pleistocene period, the early Khvalyn (40-70 thousand years ago, the maximum level is 47 abs. m, which is 74 m higher than the modern one) and the late Khvalyn (10-20 thousand years ago, the rise level up to 0 abs. m). These transgressions were separated by a deep Enotaevskaya regression (22-17 thousand years ago), when the sea level dropped to -64 abs. m and was 37 m lower than the modern one.

Rice. 4. Fluctuations in the level of the Caspian Sea over the past 10 thousand years. P is the natural range of fluctuations in the level of the Caspian Sea under climatic conditions characteristic of the subatlantic epoch of the Holocene (risk zone). I-IV - stages of the New Caspian transgression; M - Mangyshlak, D - Derbent regression

Significant fluctuations in the level of the Caspian also occurred during the New Caspian stage of its history, which coincided with the Holocene (the last 10 thousand years). After the Mangyshlak regression (10 thousand years ago, a level decrease to -50 abs. m), five stages of the New Caspian transgression were noted, separated by small regressions (Fig. 4). Following sea level fluctuations, its transgressions and regressions, the outline of the reservoir also changed (Fig. 5).

Over the historical time (2000 years), the range of changes in the average level of the Caspian Sea was 7 m - from - 32 to - 25 abs. m (see Fig. 4). The minimum level in the last 2000 years was during the Derbent regression (VI-VII centuries AD), when it decreased to - 32 abs. m. During the time that has passed since the Derbent regression, the average sea level has changed in an even narrower range - from -30 to -25 abs. m. This range of level changes is called the risk zone.

Thus, the level of the Caspian has experienced fluctuations before, and in the past they were more significant than in the 20th century. Such periodic fluctuations are a normal manifestation of the unstable state of a closed reservoir with variable conditions at the outer boundaries. Therefore, there is nothing unusual in the lowering and rising of the level of the Caspian Sea.

Fluctuations in the level of the Caspian Sea in the past, apparently, did not lead to the irreversible degradation of its biota. Of course, sharp drops in sea level created temporary unfavorable conditions, for example, for fish stocks. However, with the rise in the level, the situation corrected itself. The natural conditions of the coastal zone (vegetation, benthic animals, fish) experience periodic changes along with fluctuations in sea level and, apparently, have a certain margin of stability and resistance to external influences. After all, the most valuable sturgeon herd has always been in the Caspian basin, regardless of fluctuations in sea level, quickly overcoming the temporary deterioration of living conditions.

Rumors that rising sea levels have caused flooding throughout the Volga Delta have not been confirmed. Moreover, it turned out that the increase in water levels, even in the lower part of the delta, is inadequate to the magnitude of the sea level rise. The increase in the water level in the lower part of the delta during the low water period did not exceed 0.2-0.3 m, and almost did not manifest itself during the flood. At the maximum level of the Caspian Sea in 1995, the backwater from the sea spread along the deepest branch of the Bakhtemir delta for no more than 90 km, and along other branches for no more than 30 km. Therefore, only islands on the seashore and a narrow coastal strip of the delta were flooded. Flooding in the upper and middle parts of the delta was associated with high floods in 1991 and 1995 (which is normal for the Volga delta) and with the unsatisfactory condition of protective dams. The reason for the weak effect of sea level rise on the regime of the Volga delta is the presence of a huge shallow coastal zone, which dampens the effect of the sea on the delta.

With regard to the negative impact of sea level rise on the economy and life of the population in the coastal zone, the following should be recalled. At the end of the last century, the sea level was higher than at present, and this was in no way perceived as an ecological disaster. And before the level was even at higher levels. Meanwhile, Astrakhan has been known since the middle of the 13th century, and Sarai-Batu, the capital of the Golden Horde, was located here in the 13th - mid-16th centuries. These and many more settlements on the coast of the Caspian Sea did not suffer from high level standing, since they were located on elevated places and at abnormal flood levels or during surges, people temporarily moved from low places to higher ones.

Why, then, are the consequences of a rise in sea level even to smaller levels perceived as a catastrophe? The reason for the enormous damage that the national economy suffers is not the rise in the level, but the thoughtless and short-sighted development of a strip of land within the mentioned risk zone, freed (as it turned out, temporarily!) From under the sea level after 1929, that is, with a decrease in the level below the mark - 26 abs. m. The buildings erected in the risk zone, of course, turned out to be flooded and partially destroyed. Now, when the territory developed and polluted by man is flooded, a dangerous ecological situation is really created, the source of which is not natural processes, but unreasonable economic activity.

ABOUT THE REASONS FOR THE CASPIAN LEVEL FLUCTUATIONS

Considering the question of the causes of fluctuations in the level of the Caspian Sea, it is necessary to pay attention to the confrontation in this area of ​​two concepts: geological and climatic. Significant contradictions in these approaches were revealed, for example, at the international conference "Caspian-95".

According to the geological concept, the causes of changes in the level of the Caspian include processes of two groups. The processes of the first group, according to geologists, lead to a change in the volume of the Caspian basin and, as a result, to changes in sea level. Such processes include vertical and horizontal tectonic movements of the earth's crust, accumulation of bottom sediments, and seismic events. The second group includes processes that, as geologists believe, affect the underground runoff into the sea, either increasing it or decreasing it. Such processes are called periodic extrusion or absorption of water, which saturate bottom sediments under the influence of changing tectonic stresses (changes in periods of compression and tension), as well as technogenic destabilization of the subsoil due to oil and gas production or underground nuclear explosions. One cannot deny the fundamental possibility of the influence of geological processes on the morphology and morphometry of the Caspian basin and underground runoff. However, at present, the quantitative relationship of geological factors with fluctuations in the level of the Caspian Sea has not been proven.

There is no doubt that tectonic movements played a decisive role in the initial stages of the formation of the Caspian depression. However, if we take into account that the Caspian Sea basin is located within a geologically heterogeneous territory, which results in periodic rather than linear tectonic movements with repeated sign changes, then one should hardly expect a noticeable change in the capacity of the basin. Not in favor of the tectonic hypothesis is also evidenced by the fact that coastlines New Caspian transgressions in all sections of the Caspian coast (with the exception of certain areas within the Apsheron archipelago) are at the same level.

There are no grounds to consider the change in the capacity of its basin due to the accumulation of precipitation to be the reason for fluctuations in the level of the Caspian Sea. The rate of filling the basin with bottom sediments, among which the main role is played by river runoff, is estimated, according to modern data, at a value of about 1 mm/year or less, which is two orders of magnitude less than the currently observed changes in sea level. Seismic deformations, which are observed only near the epicenter and attenuate at close distances from it, cannot have any significant effect on the volume of the Caspian Basin.

As for the periodic large-scale discharge of groundwater into the Caspian Sea, its mechanism is still unclear. At the same time, this hypothesis is contradicted, according to E.G. Maev, firstly, the undisturbed stratification of interstitial waters, indicating the absence of noticeable migrations of waters through the thickness of bottom sediments, and secondly, the absence of proven powerful hydrological, hydrochemical and sedimentation anomalies in the sea, which should have accompanied a large-scale discharge of groundwater capable of affect changes in water levels.

The main evidence of the insignificant role of geological factors at present is a convincing quantitative confirmation of the plausibility of the second, climatic, or rather, water-balance concept of fluctuations in the Caspian level.

CHANGES IN THE COMPONENTS OF THE CASPIAN WATER BALANCE AS THE MAIN CAUSE OF ITS LEVEL FLUCTUATIONS

For the first time, fluctuations in the level of the Caspian Sea were explained by a change climatic conditions(more specifically, the runoff of rivers, evaporation and precipitation on the surface of the sea) by E.Kh. Lenz (1836) and A.I. Voeikov (1884). Later, the leading role of changes in the components of the water balance in sea level fluctuations was again and again proved by hydrologists, oceanologists, physicogeographers and geomorphologists.

The key to most of the studies mentioned is the compilation of the water balance equation and the analysis of its components. The meaning of this equation is as follows: the change in the volume of water in the sea is the difference between the incoming (river and underground runoff, atmospheric precipitation on the sea surface) and outgoing (evaporation from the sea surface and outflow of water into the Kara-Bogaz-Gol Bay) components of the water balance. The change in the level of the Caspian is the quotient of dividing the change in the volume of its waters by the area of ​​the sea. The analysis showed that the leading role in the water balance of the sea belongs to the ratio of the flow of the Volga, Ural, Terek, Sulak, Samur, Kura rivers and visible or effective evaporation, the difference between evaporation and atmospheric precipitation on the sea surface. An analysis of the components of the water balance revealed that the largest contribution (up to 72% of the dispersion) to the level variability comes from the inflow of river waters, and more specifically, the runoff formation zone in the Volga basin. As for the reasons for the change in the flow of the Volga itself, they are associated, as many researchers believe, with the variability of atmospheric precipitation (mainly winter) in the river basin. And the mode of precipitation, in turn, is determined by the circulation of the atmosphere. It has long been proven that the increase in precipitation in the Volga basin is facilitated by the latitudinal type of atmospheric circulation, while the decrease is facilitated by the meridional type.

V.N. Malinin revealed that the root cause of moisture entering the Volga basin should be sought in the North Atlantic, and specifically in the Norwegian Sea. It is there that an increase in evaporation from the sea surface leads to an increase in the amount of moisture transferred to the continent, and, accordingly, to an increase in atmospheric precipitation in the Volga basin. The latest data on the water balance of the Caspian Sea, received by the staff of the State Oceanographic Institute R.E. Nikonova and V.N. Bortnik, are given with the author's clarifications in Table. 1. These data convincingly prove that the main reasons for both the rapid drop in sea level in the 1930s and the sharp rise in 1978-1995 were changes in river flow, as well as apparent evaporation.

Keeping in mind that river runoff is one of the main factors affecting the water balance and, as a result, the level of the Caspian Sea (and the Volga runoff provides at least 80% of the total river runoff in the sea and about 70% of the incoming part of the Caspian water balance), it would be interesting to find a connection between sea level and the flow of one Volga, measured most accurately. Direct correlation of these quantities does not give satisfactory results.

However, the relationship between the sea level and the Volga runoff is well traced if the river runoff is not taken into account for each year, but the ordinates of the difference integral runoff curve are taken, that is, the sequential sum of the normalized deviations of the annual runoff values ​​from the long-term average value (norm). Even a visual comparison of the course of the average annual levels of the Caspian Sea and the difference integral curve of the Volga runoff (see Fig. 2) makes it possible to reveal their similarity.

For the entire 98-year period of observations of the Volga runoff (the village of Verkhneye Lebyazhye at the head of the delta) and the sea level (Makhachkala), the correlation coefficient of the relationship between the sea level and the ordinates of the difference integral runoff curve was 0.73. If we discard years with small level changes (1900-1928), then the correlation coefficient increases to 0.85. If for analysis we take a period with a rapid decline (1929-1941) and a rise in the level (1978-1995), then the overall correlation coefficient will be 0.987, and separately for both periods 0.990 and 0.979, respectively.

The presented calculation results fully confirm the conclusion that during periods of a sharp decrease or rise in sea level, the levels themselves are closely related to the runoff (more precisely, to the sum of its annual deviations from the norm).

A special task is to assess the role of anthropogenic factors in fluctuations in the level of the Caspian Sea, and above all, the reduction in river flow due to its irretrievable losses for filling reservoirs, evaporation from the surface of artificial reservoirs, and water withdrawal for irrigation. It is believed that since the 1940s, irretrievable water consumption has been steadily increasing, which has led to a reduction in the inflow of river waters to the Caspian Sea and an additional decrease in its level compared to the natural one. According to V.N. Malinin, by the end of the 1980s, the difference between the actual sea level and the restored (natural) level reached almost 1.5 m. about 26 km3/year). If it were not for the withdrawal of river runoff, then the rise in sea level would have begun not in the late 70s, but in the late 50s.

The growth of water consumption in the Caspian basin by 2000 was projected first to 65 km3/year, and then to 55 km3/year (36 of them were in the Volga). Such an increase in irretrievable losses of river runoff should have lowered the level of the Caspian by more than 0.5 m by 2000. In connection with the assessment of the impact of irreversible water consumption on the level of the Caspian, we note the following. First, estimates of water withdrawal volumes and evaporation losses from the surface of reservoirs in the Volga basin found in the literature are apparently significantly overestimated. Secondly, forecasts of water consumption growth turned out to be erroneous. The forecasts included the rate of development of water-consuming sectors of the economy (especially irrigation), which not only turned out to be unrealistic, but also gave way to a decline in production in recent years. In fact, as A.E. Asarin (1997), by 1990 water consumption in the Caspian basin was about 40 km3/year, and has now decreased to 30-35 km3/year (in the Volga basin to 24 km3/year). Therefore, the "anthropogenic" difference between the natural and actual sea levels is currently not as large as predicted.

ON POSSIBLE FLUCTUATIONS OF THE CASPIAN LEVEL IN THE FUTURE

The author does not set himself the goal of analyzing in detail the numerous forecasts of fluctuations in the level of the Caspian Sea (this is an independent and difficult task). The main conclusion from the assessment of the results of forecasting fluctuations in the level of the Caspian can be drawn as follows. Although the forecasts were based on completely different approaches (both deterministic and probabilistic), there was not a single reliable forecast. The main difficulty in using deterministic forecasts based on the sea water balance equation is the lack of development of the theory and practice of ultra-long-term forecasts of climate change over large areas.

When the sea level decreased in the 1930s and 1970s, most researchers predicted its further fall. In the last two decades, when sea level rise began, most forecasts predicted an almost linear and even accelerating rise in level to -25 and even -20 abs. m and above at the beginning of the XXI century. In this case, three factors were not taken into account. First, the periodic nature of fluctuations in the level of all endorheic reservoirs. The instability of the Caspian level and its periodic nature are confirmed by the analysis of its current and past fluctuations. Secondly, at sea level close to - 26 abs. m, the flooding of large sor bays on the northeastern coast of the Caspian Sea - Dead Kultuk and Kaydak, as well as low-lying territories in other places of the coast, which have dried up at a low level, will begin. This would lead to an increase in the area of ​​shallow waters and, as a consequence, an increase in evaporation (up to 10 km3/year). With a higher sea level, the outflow of water to Kara-Bogaz-Gol will increase. All this should stabilize or at least slow down the level growth. Thirdly, level fluctuations under the conditions of the modern climatic epoch (the last 2000 years), as shown above, are limited by the risk zone (from -30 to -25 abs. m). Taking into account the anthropogenic decrease in runoff, the level is unlikely to exceed the mark of 26-26.5 abs. m.

The decrease in average annual levels in the last four years by a total of 0.34 m, possibly indicates that in 1995 the level reached its maximum (-26.66 abs. m), and a change in the trend of the Caspian level. In any case, the prediction that the sea level is unlikely to exceed 26 abs. m, apparently justified.

In the 20th century, the level of the Caspian Sea changed within 3.5 m, first dropping and then rising sharply. This behavior of the Caspian Sea is the normal state of a closed reservoir as an open dynamic system with variable conditions at its inlet.

Each combination of incoming (river runoff, precipitation on the sea surface) and outgoing (evaporation from the surface of the reservoir, outflow to the Kara-Bogaz-Gol Bay) components of the Caspian water balance corresponds to its own level of equilibrium. Since the components of the water balance of the sea also change under the influence of climatic conditions, the level of the reservoir fluctuates, trying to reach an equilibrium state, but never reaches it. Ultimately, the trend of changing the level of the Caspian in given time depends on the ratio of precipitation minus evaporation in the watershed (in the basins of the rivers that feed it) and evaporation minus precipitation over the reservoir itself. There is really nothing unusual about the recent rise of the Caspian Sea level by 2.3 m. Such level changes have happened many times in the past and did not cause irreparable damage to the natural resources of the Caspian. The current rise in sea level has become a catastrophe for the economy of the coastal zone only because of the unreasonable development of this risk zone by man.

Vadim Nikolaevich Mikhailov, Doctor of Geography, Professor of the Department of Terrestrial Hydrology of the Faculty of Geography of Moscow State University, Honored Worker of Science of the Russian Federation, full member of the Academy of Water Management Sciences. Area of ​​scientific interests – hydrology and water resources, interaction of rivers and seas, deltas and estuaries, hydroecology. Author and co-author of about 250 scientific works, including 11 monographs, two textbooks, four scientific and methodological manuals.